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1. In a typical root, the main function of the root cap is to:
ⓐ. Absorb water by increasing surface area
ⓑ. Protect the root apical meristem during penetration of soil
ⓒ. Conduct food from leaves to root
ⓓ. Produce lateral roots from its tissue
Correct Answer: Protect the root apical meristem during penetration of soil
Explanation: The root cap is a thimble-like covering present at the root tip that shields the delicate apical meristem from mechanical injury as the root pushes through soil particles. Its cells are continuously worn off and replaced, maintaining protection while allowing growth. The cap also secretes mucilage that lubricates the tip, reducing friction and easing soil penetration. This structure is therefore essential for safe, continuous root elongation. Additionally, it helps the root sense gravity, guiding downward growth. Hence, its key role is protective support for the growing root tip.
2. The zone of a root where most water and mineral absorption occurs is mainly due to the presence of:
ⓐ. Lateral roots with thick bark
ⓑ. Mature xylem vessels near the base
ⓒ. Numerous root hairs that increase surface area
ⓓ. A well-developed root cap at the tip
Correct Answer: Numerous root hairs that increase surface area
Explanation: The absorption zone of a root is characterized by a large number of thin-walled root hairs that arise from epidermal cells. These root hairs greatly increase the surface area in contact with soil water, making uptake of water and dissolved minerals efficient. Their walls are permeable, and their close association with soil particles helps in rapid diffusion and osmosis. This region is functionally specialized for absorption rather than conduction or protection. Because root hairs are short-lived and constantly replaced, absorption remains continuous. Therefore, the presence of root hairs is the main reason for maximum absorption in this zone.
3. A student uproots two seedlings: one shows a primary root with lateral branches; the other shows many similar roots arising from the base of the stem. The second seedling most likely has a:
ⓐ. Fibrous root system, typical of monocots
ⓑ. Tap root system, typical of dicots
ⓒ. Tap root system, typical of monocots
ⓓ. Fibrous root system, typical of dicots
Correct Answer: Fibrous root system, typical of monocots
Explanation: A fibrous root system consists of many roots of nearly equal size that originate from the base of the stem, usually replacing the short-lived primary root. This pattern is commonly seen in monocot plants such as grasses and cereals. In contrast, dicots generally retain a prominent primary root that forms a tap root system with lateral branching. The observed “many similar roots from stem base” is a hallmark of fibrous roots. This arrangement provides strong anchorage and effective absorption over a wide soil area. Hence, the second seedling is best identified as having a fibrous root system typical of monocots.
4. Which pair is correctly matched with a root modification and its primary adaptive role?
ⓐ. Stilt roots — gaseous exchange in marshy soil
ⓑ. Pneumatophores — mechanical support in maize
ⓒ. Prop roots — absorption of atmospheric moisture in epiphytes
ⓓ. Pneumatophores — respiration in waterlogged conditions
Correct Answer: Pneumatophores — respiration in waterlogged conditions
Explanation: Pneumatophores are specialized aerial roots commonly found in plants growing in waterlogged, oxygen-poor soils, where normal roots cannot obtain enough oxygen for respiration. These roots grow upward out of the soil and bear pores (lenticels) that facilitate gaseous exchange with the atmosphere. This adaptation ensures adequate oxygen supply to underground tissues. It is especially associated with mangrove habitats where soil is saturated and anaerobic. Because the primary challenge is lack of oxygen, the key function is respiration rather than support or moisture absorption. Therefore, pneumatophores are correctly matched with respiration in waterlogged conditions.
5. In leguminous plants, root nodules are primarily significant because they:
ⓐ. Store starch to support seed formation
ⓑ. House nitrogen-fixing bacteria that enrich the plant’s nitrogen supply
ⓒ. Absorb oxygen efficiently in flooded soils
ⓓ. Provide climbing support by coiling around objects
Correct Answer: House nitrogen-fixing bacteria that enrich the plant’s nitrogen supply
Explanation: Root nodules in leguminous plants contain symbiotic nitrogen-fixing bacteria (commonly Rhizobium) that convert atmospheric nitrogen into usable nitrogenous compounds. This biological nitrogen fixation supports protein synthesis and overall growth, especially in nitrogen-poor soils. The plant provides carbohydrates and a suitable environment for the bacteria, making it a mutualistic relationship. Nodules often contain a pigment that helps maintain oxygen levels optimal for nitrogenase activity, protecting the fixation process. This adaptation improves soil fertility and reduces dependence on external nitrogen sources. Hence, the primary significance of nodules is housing nitrogen-fixing bacteria that supplement the plant’s nitrogen requirement.
6. Mycorrhiza is best described as an association between:
ⓐ. A fungus and roots, improving mineral and water uptake
ⓑ. Bacteria and stems, aiding cellulose digestion
ⓒ. Algae and roots, enabling photosynthesis underground
ⓓ. Virus and roots, inducing rapid cell division
Correct Answer: A fungus and roots, improving mineral and water uptake
Explanation: Mycorrhiza refers to a symbiotic association between fungal hyphae and plant roots in which both partners benefit. The fungal network extends far beyond the root surface, increasing the effective absorptive area and enhancing uptake of water and minerals, especially phosphates. In return, the plant supplies the fungus with organic food derived from photosynthesis. This relationship can improve plant growth, tolerance to drought, and resistance to certain root pathogens. It is common in many flowering plants and plays an important role in nutrient cycling in ecosystems. Therefore, mycorrhiza is correctly defined as a fungus–root association that improves mineral and water absorption.
7. Aerial roots covered with a spongy, multilayered tissue that absorbs atmospheric moisture are most characteristically found in:
ⓐ. Desert succulents for water storage
ⓑ. Wheat plants for rapid absorption in topsoil
ⓒ. Mangroves for oxygen uptake in mud
ⓓ. Epiphytic orchids for moisture absorption from air
Correct Answer: Epiphytic orchids for moisture absorption from air
Explanation: Many epiphytic orchids possess aerial adventitious roots that are covered by a specialized tissue called velamen. Velamen is multilayered and spongy, allowing rapid absorption of moisture from humid air and rainwater, which is crucial because epiphytes grow on other plants without direct access to soil. This tissue also reduces water loss by limiting transpiration and protects roots from mechanical damage. Since orchids often rely on atmospheric sources for water and dissolved minerals, such roots are a key survival adaptation. The presence of velamen is therefore strongly associated with epiphytic orchids. Hence, epiphytic orchids are the best match.
8. Which example correctly represents a supporting root modification?
ⓐ. Conical roots in carrot that store food
ⓑ. Nodulated roots in pea for nitrogen fixation
ⓒ. Prop roots in banyan that provide pillar-like support
ⓓ. Pneumatophores in mangroves for oxygen uptake
Correct Answer: Prop roots in banyan that provide pillar-like support
Explanation: Prop roots are adventitious roots that arise from branches and grow downward into the soil, where they thicken and act like supporting pillars. This modification increases mechanical stability, allowing large trees like banyan to spread widely without branch collapse. The roots function primarily in support rather than storage or respiration. As they mature, they become woody and can bear substantial weight, effectively extending the trunk’s supportive base. This adaptation is especially useful in trees with extensive horizontal branching. Therefore, prop roots in banyan correctly represent a supporting root modification.
9. Storage roots in sweet potato are best categorized as:
ⓐ. Modified primary roots that thicken uniformly
ⓑ. Modified adventitious roots that store food
ⓒ. Modified lateral roots that store oxygen
ⓓ. Modified root caps that store starch
Correct Answer: Modified adventitious roots that store food
Explanation: Sweet potato develops swollen roots that store reserve food materials, but these are adventitious roots arising from the stem region rather than thickened primary roots. Such storage helps the plant survive unfavorable conditions and supports regrowth and reproduction by providing an energy reserve. Adventitious roots can undergo enlargement due to accumulation of carbohydrates, leading to tuberous structures in certain plants. This is distinct from carrot and radish, where storage occurs mainly in the primary tap root. Because sweet potato storage structures originate adventitiously and function in food storage, they are classified as modified adventitious storage roots.
10. Which statement best distinguishes the region of maturation (differentiation) in a young root?
ⓐ. It bears root hairs and shows differentiation of tissues
ⓑ. It contains actively dividing cells protected by root cap
ⓒ. It consists of elongating cells increasing root length rapidly
ⓓ. It is the oldest region where lateral roots never arise
Correct Answer: It bears root hairs and shows differentiation of tissues
Explanation: The region of maturation, also called the differentiation zone, is where root cells complete their specialization into permanent tissues. It is characterized by the presence of root hairs that arise from the epidermis and greatly enhance absorption of water and minerals. Unlike the meristematic zone (cell division) or elongation zone (rapid length increase), this zone focuses on functional maturity and tissue differentiation. Vascular tissues become more effective for conduction here, while epidermal modifications support absorption. Root hairs are a prominent external indicator of this region’s function. Therefore, the region of maturation is correctly identified by root hairs and differentiated tissues.
11. The primary reason the root tip can push through compact soil without damaging its growth tissue is because:
ⓐ. The epidermis at the tip becomes heavily cutinized
ⓑ. The root cap covers and protects the apical meristem
ⓒ. The pericycle forms a hard protective ring at the tip
ⓓ. The endodermis develops thick Casparian strips early
Correct Answer: The root cap covers and protects the apical meristem
Explanation: The root apical meristem is made of actively dividing, delicate cells that would be easily injured by friction and mechanical pressure in soil. The root cap forms a protective covering over this meristem and is continuously renewed as its outer cells get worn away. This ensures uninterrupted root growth even in abrasive conditions. The cap also helps in smooth penetration by maintaining a barrier between soil particles and the meristematic tissue. Because protection of the growing point is essential for elongation, the root cap is a key adaptation. Hence, its protective coverage is the main reason the root tip can advance safely through soil.
12. A major role of the mucilage secreted by root cap cells is to:
ⓐ. Increase light absorption at the root tip
ⓑ. Stimulate chlorophyll formation in the cortex
ⓒ. Convert nitrates into amino acids near the tip
ⓓ. Reduce friction and help the root move through soil
Correct Answer: Reduce friction and help the root move through soil
Explanation: Root cap cells secrete mucilage, a slimy substance that coats the root tip and surrounding soil particles. This mucilage acts as a lubricant, lowering friction as the root penetrates through the soil matrix. By binding fine soil particles, it creates a smoother path and reduces mechanical resistance against the growing tip. This support complements the protective function of the root cap by minimizing abrasion and cell damage. The lubricating effect is especially valuable in dry or compact soils where resistance is higher. Therefore, reducing friction to facilitate soil penetration is a major function of root cap mucilage.
13. The perception of gravity that helps roots grow downward is mainly linked to specialized cells located in the:
ⓐ. Root cap region (statocyte-containing tissue)
ⓑ. Pericycle of the maturation zone
ⓒ. Endodermis with Casparian strips
ⓓ. Phloem near the root base
Correct Answer: Root cap region (statocyte-containing tissue)
Explanation: The root cap contains specialized gravity-sensing cells commonly termed statocytes, which help the root respond to gravitational pull. These cells contain dense starch-filled bodies (statoliths) that settle under gravity and provide directional information. This sensing mechanism allows the root tip to orient growth downward, supporting proper anchorage and access to water and minerals. Because the root cap is positioned at the tip, it is ideally located to detect directional cues and guide growth. This function is closely integrated with the root’s growth processes at the apex. Hence, gravity perception is primarily associated with statocyte-containing tissue in the root cap region.
14. The zone just behind the root cap where cells show maximum mitotic activity is the:
ⓐ. Zone of elongation
ⓑ. Zone of maturation
ⓒ. Meristematic zone
ⓓ. Region of secondary growth
Correct Answer: Meristematic zone
Explanation: The meristematic zone lies immediately behind the root cap and is characterized by rapid, continuous cell division. Cells here are small, thin-walled, have dense cytoplasm, prominent nuclei, and minimal vacuolation—features typical of actively dividing tissue. This zone produces new cells that later enlarge in the elongation zone and then differentiate in the maturation zone. Since root lengthening depends on a steady supply of new cells, mitosis is most intense here. The root cap protects this sensitive region while it maintains growth potential. Therefore, the region of maximum mitotic activity behind the root cap is the meristematic zone.
15. Which cellular feature is most typical of root meristematic cells (compared to cells in the maturation zone)?
ⓐ. Large central vacuole and thin cytoplasm
ⓑ. Dense cytoplasm with a prominent nucleus and small vacuoles
ⓒ. Thick cutinized walls and abundant intercellular spaces
ⓓ. Fully developed xylem vessels with lignified walls
Correct Answer: Dense cytoplasm with a prominent nucleus and small vacuoles
Explanation: Meristematic cells are specialized for rapid division, so they maintain dense cytoplasm and a large, prominent nucleus to support active DNA replication and mitosis. Vacuoles are small or poorly developed because extensive vacuolation is more typical of mature cells that have stopped dividing. Cell walls remain thin and flexible, supporting frequent cytokinesis. In contrast, cells in the maturation zone are larger, highly vacuolated, and structurally specialized for absorption or conduction. These differences reflect the functional shift from division to differentiation. Hence, dense cytoplasm with a prominent nucleus and small vacuoles best describes meristematic cells.
16. A small region within the root apical meristem that divides slowly and helps maintain the meristem’s organization is called the:
ⓐ. Quiescent center
ⓑ. Root hair zone
ⓒ. Casparian zone
ⓓ. Vascular cambium
Correct Answer: Quiescent center
Explanation: The quiescent center is a group of cells in the root apical meristem that shows relatively low mitotic activity under normal conditions. Despite slow division, it plays an important role in maintaining the surrounding meristematic initials by regulating organization and stability of the root apex. If the actively dividing cells are damaged, quiescent center cells can become more active and help in regeneration of meristematic tissue. This contributes to sustained root growth and recovery from injury. Its presence supports long-term integrity of the root growth region. Therefore, the correct term for this slowly dividing, organizing region is the quiescent center.
17. In the root tip, the correct sequence of regions from the extreme tip moving upward is:
ⓐ. Meristematic zone → root cap → elongation zone → maturation zone
ⓑ. Root cap → maturation zone → elongation zone → meristematic zone
ⓒ. Root cap → meristematic zone → elongation zone → maturation zone
ⓓ. Root cap → elongation zone → meristematic zone → maturation zone
Correct Answer: Root cap → meristematic zone → elongation zone → maturation zone
Explanation: The root cap occupies the extreme tip and protects the actively dividing tissues immediately behind it. Just above the cap lies the meristematic zone, where cells divide repeatedly to produce new cells for growth. These newly formed cells then enter the elongation zone, where they increase in size and push the root tip forward, contributing significantly to root lengthening. Above that lies the maturation (differentiation) zone, where cells specialize and root hairs commonly develop for absorption. This ordered arrangement reflects the developmental progression from protection to division, elongation, and specialization. Hence, the correct sequence is root cap → meristematic zone → elongation zone → maturation zone.
18. If the root cap is repeatedly removed from a growing root tip, the most immediate effect on the plant is likely to be:
ⓐ. Increased photosynthesis in root tissues
ⓑ. Immediate formation of lateral roots at the tip
ⓒ. Higher risk of damage to the apical meristem during soil penetration
ⓓ. Instant conversion of the tap root into a fibrous root system
Correct Answer: Higher risk of damage to the apical meristem during soil penetration
Explanation: The root cap is the protective structure that shields the apical meristem from mechanical injury and abrasion as the root moves through soil. When it is repeatedly removed, the delicate meristematic cells become directly exposed to friction and pressure. This increases the chance of physical damage, which can disrupt cell division and impair root elongation. The loss of cap-derived mucilage also reduces lubrication, further increasing resistance during penetration. Because growth depends on the integrity of the meristem, injury at the tip can significantly slow or alter root development. Therefore, the most immediate consequence is increased damage risk to the apical meristem during soil penetration.
19. A key functional outcome of continuous cell division in the meristematic zone is the:
ⓐ. Direct formation of root hairs on the dividing cells
ⓑ. Continuous supply of new cells for elongation and differentiation
ⓒ. Immediate development of lignified xylem vessels at the tip
ⓓ. Rapid deposition of cuticle to prevent water loss in roots
Correct Answer: Continuous supply of new cells for elongation and differentiation
Explanation: The meristematic zone acts as the primary source of new cells in a growing root, producing cells through repeated mitosis. These newly formed cells do not remain meristematic; they move into the elongation zone where they enlarge, contributing to root lengthening. Later, they enter the maturation zone, where they differentiate into specialized tissues such as epidermis, cortex, and vascular elements. This flow from division to elongation to differentiation is essential for continuous root growth and functional development. Without a steady supply of new cells, both elongation and tissue specialization would be limited. Hence, the main outcome of meristematic division is a continuous supply of new cells for elongation and differentiation.
20. A botanist observes small, actively dividing cells with dense cytoplasm directly behind a protective cap-like structure at the root tip. This region is best identified as:
ⓐ. Root apical meristem (meristematic zone)
ⓑ. Root hair zone (absorption zone)
ⓒ. Zone of maturation with differentiated tissues
ⓓ. Region of secondary growth with cambial activity
Correct Answer: Root apical meristem (meristematic zone)
Explanation: The presence of a cap-like protective structure indicates the root cap, which covers the extreme tip of the root. Immediately behind it lies the root apical meristem, where cells are small, tightly packed, and show active mitotic division. These cells have dense cytoplasm and prominent nuclei, reflecting their high metabolic and division activity. This region is responsible for producing new cells that later elongate and differentiate, driving root growth. Such features clearly distinguish it from the root hair zone and maturation zone, which contain larger, more specialized cells. Therefore, the observed region is correctly identified as the root apical meristem (meristematic zone).
21. The primary reason the zone of elongation contributes most to increase in root length is that cells in this zone:
ⓐ. Differentiate into root hair cells for absorption
ⓑ. Rapidly increase in size due to vacuolation and cell wall loosening
ⓒ. Divide repeatedly to add more cells at the tip
ⓓ. Develop lignified vessels to strengthen the root tip
Correct Answer: Rapidly increase in size due to vacuolation and cell wall loosening
Explanation: In the zone of elongation, newly formed cells expand dramatically, mainly because their vacuoles enlarge and the cell walls become more extensible. This expansion pushes the root tip forward through the soil, producing a noticeable increase in length even without a large increase in cell number. The process is driven by water uptake and controlled loosening of the cell wall, allowing turgor pressure to stretch the cells. Because many cells elongate simultaneously in this region, the cumulative effect on root length is substantial. This is why elongation, not differentiation, is the most direct contributor to rapid length increase. Hence, rapid cell enlargement via vacuolation and wall loosening is the key reason.
22. A root region where cells stop increasing in length and begin specializing into permanent tissues is the:
ⓐ. Root cap region
ⓑ. Meristematic zone
ⓒ. Zone of elongation
ⓓ. Zone of maturation (differentiation)
Correct Answer: Zone of maturation (differentiation)
Explanation: The zone of maturation is the region where cells complete their growth in size and begin differentiating into specialized permanent tissues such as epidermis, cortex, endodermis, and vascular elements. This shift from general growth to specialization allows the root to perform functions like absorption, conduction, and support efficiently. Root hairs typically appear in this zone, indicating epidermal differentiation for absorption. Compared to the elongation zone, cells here have more stable size and structure and develop features suited to their roles. This region therefore marks the transition to functional maturity. Hence, the correct region is the zone of maturation (differentiation).
23. Root hairs are most accurately described as:
ⓐ. Unicellular extensions of epidermal cells that increase absorptive surface area
ⓑ. Multicellular outgrowths of cortex that store starch reserves
ⓒ. Modified endodermal cells that regulate ion movement into xylem
ⓓ. Lateral roots that arise from the pericycle and branch repeatedly
Correct Answer: Unicellular extensions of epidermal cells that increase absorptive surface area
Explanation: Root hairs are slender, tube-like outgrowths of individual epidermal cells that significantly increase the surface area available for absorption. Being unicellular and thin-walled, they maintain close contact with soil particles and facilitate efficient uptake of water and dissolved minerals. They are short-lived and are continuously replaced as the root grows, ensuring sustained absorption. Their placement in the maturation region aligns with the need for differentiated epidermal function. Root hairs do not originate from cortex or pericycle and do not function as storage structures. Therefore, they are best described as unicellular epidermal extensions increasing absorptive area.
24. If a young root is shifted from moist soil to a very dry medium, the earliest functional impact is most likely a reduction in:
ⓐ. Cell division in the meristem due to immediate DNA damage
ⓑ. Formation of lateral roots because pericycle cells die instantly
ⓒ. Water absorption because root hairs lose effective contact with moisture
ⓓ. Secondary growth because cambium activity stops within minutes
Correct Answer: Water absorption because root hairs lose effective contact with moisture
Explanation: Root hairs are the primary structures responsible for absorbing water from the soil because they provide a large surface area and intimate contact with soil water films. In a dry medium, the thin water film around soil particles decreases, and root hairs cannot maintain effective contact for osmosis and diffusion. As a result, water uptake drops quickly even before deeper developmental changes occur in division or differentiation zones. The immediate limitation is availability and accessibility of water at the root surface rather than sudden structural collapse of internal tissues. This directly affects the plant’s hydration status and mineral uptake coupled to water flow. Hence, reduced water absorption due to ineffective root hair contact is the earliest impact.
25. A key anatomical reason root hairs are effective at absorption is that they:
ⓐ. Have thick cutinized walls that prevent water loss to soil
ⓑ. Are thin-walled and greatly increase surface area at the root–soil interface
ⓒ. Contain lignified tissues that actively pump minerals into the plant
ⓓ. Possess stomata-like pores that open and close to regulate uptake
Correct Answer: Are thin-walled and greatly increase surface area at the root–soil interface
Explanation: Root hairs are highly effective absorptive structures because they are long, narrow, and numerous, creating a large surface area in contact with the soil. Their walls are thin and permeable, allowing easy movement of water by osmosis and minerals by diffusion and active transport through the plasma membrane. By extending between soil particles, they access water films that the main root surface cannot reach efficiently. Their close association with soil also supports continuous ion exchange and uptake of dissolved nutrients. This design maximizes absorption without requiring thick protective layers. Therefore, thin walls and increased surface area at the root–soil interface make root hairs effective.
26. Which observation best indicates that a root segment belongs to the zone of elongation rather than the maturation zone?
ⓐ. Cells are increasing rapidly in length with limited tissue specialization
ⓑ. Numerous root hairs are visible as fine, fuzzy outgrowths
ⓒ. Epidermal cells show fully differentiated hair and non-hair regions
ⓓ. Mature xylem and phloem appear fully functional with stable anatomy
Correct Answer: Cells are increasing rapidly in length with limited tissue specialization
Explanation: The zone of elongation is characterized by rapid increase in cell length, which contributes directly to root growth in length. In this region, cells have begun to expand but have not yet fully specialized into permanent tissue types. Root hairs and clear epidermal differentiation are typically associated with the maturation zone, not the elongation zone. Similarly, fully functional, mature vascular tissues are more evident as differentiation progresses upward. Therefore, the best indicator of the elongation zone is predominance of rapid cell elongation with minimal specialization. Hence, observing actively lengthening cells with limited differentiation identifies the zone of elongation.
27. Root hairs are most commonly present because the epidermis in the maturation zone differentiates into a specialized layer called:
ⓐ. Endodermis
ⓑ. Hypodermis
ⓒ. Epidermis with a thick cuticle
ⓓ. Piliferous layer
Correct Answer: Piliferous layer
Explanation: In the maturation zone, the epidermis differentiates into a root hair-bearing region often referred to as the piliferous layer. This layer gives rise to root hairs, which are extensions of epidermal cells adapted specifically for absorption. The piliferous layer is typically thin and lacks a heavy cuticle, which would otherwise hinder water uptake. Its structural specialization supports intimate contact with the soil and maximizes absorptive efficiency. This differentiation aligns with the functional role of the maturation zone as the main site of absorption. Therefore, the root hair-bearing epidermis is correctly termed the piliferous layer.
28. Which statement correctly links the elongation zone and maturation zone in terms of root growth and function?
ⓐ. Both zones primarily protect the root tip from mechanical injury
ⓑ. Elongation zone forms root hairs, while maturation zone produces new cells by mitosis
ⓒ. Elongation zone increases root length by cell expansion, while maturation zone specializes tissues for absorption and conduction
ⓓ. Maturation zone has maximum cell enlargement, while elongation zone has fully differentiated xylem and phloem
Correct Answer: Elongation zone increases root length by cell expansion, while maturation zone specializes tissues for absorption and conduction
Explanation: The elongation zone contributes to root lengthening mainly through rapid cell enlargement, which physically pushes the root forward in the soil. In contrast, the maturation zone is where cells undergo differentiation into permanent tissues, enabling specialized functions such as absorption through root hairs and transport through developing vascular tissues. This division of roles ensures that growth and function progress in an organized sequence along the root axis. The root thus elongates first and then becomes functionally efficient as tissues mature. The two zones are therefore complementary: one drives extension, the other enables mature physiological activity. Hence, the correct linkage is elongation by expansion and maturation by specialization.
29. Root hairs are generally absent near the extreme tip of the root mainly because:
ⓐ. The root cap releases chemicals that dissolve root hairs instantly
ⓑ. The meristematic and elongation regions have cells not yet fully differentiated to form hairs
ⓒ. The pericycle suppresses epidermal outgrowths until lateral roots appear
ⓓ. The endodermis prevents epidermal cells from contacting soil near the tip
Correct Answer: The meristematic and elongation regions have cells not yet fully differentiated to form hairs
Explanation: Root hairs form when epidermal cells become functionally specialized, which occurs in the maturation zone after cells have completed division and elongation. Near the tip, cells in the meristematic region are actively dividing, and cells in the elongation zone are primarily expanding in size; neither region has fully differentiated epidermal cells capable of producing stable hair outgrowths. Hair formation requires specific cellular architecture and membrane transport machinery associated with mature epidermal cells. This developmental timing ensures that root hairs appear where tissues can support efficient absorption. Therefore, absence of root hairs near the tip is mainly due to incomplete differentiation in meristematic and elongation regions.
30. A student notes that root hairs are short-lived and disappear as the root segment becomes older. The most accurate interpretation is that root hairs:
ⓐ. Are replaced by stomata-like structures on older root regions
ⓑ. Are continuously formed in the maturation zone and lost as that region ages and moves upward
ⓒ. Convert into lateral roots when absorption demand increases
ⓓ. Become lignified and transform into supportive fibers over time
Correct Answer: Are continuously formed in the maturation zone and lost as that region ages and moves upward
Explanation: Root hairs are transient epidermal outgrowths that develop in the maturation zone where absorption is active. As the root continues to grow, the region bearing root hairs shifts forward, and older segments move away from the actively absorbing zone. In older regions, epidermal cells often lose the conditions needed to maintain root hairs, and the hairs break off or degenerate. This turnover keeps absorption concentrated near the actively growing portion of the root where soil contact and nutrient availability are optimal. Continuous formation at the newer maturation region maintains effective uptake. Hence, root hairs are continuously formed in the maturation zone and lost as that region ages and moves upward.
31. A seedling shows one prominent primary root that persists and gives rise to secondary and tertiary roots. This root system is best identified as:
ⓐ. Tap root system
ⓑ. Fibrous root system
ⓒ. Adventitious root system
ⓓ. Pneumatophore system
Correct Answer: Tap root system
Explanation: A tap root system develops when the radicle (primary root) of the embryo persists as the main root and continues to grow downward. From this primary root, lateral branches arise as secondary and tertiary roots, creating a clear main axis with side branches. This pattern is typical of many dicot plants and is strongly associated with deep anchorage and access to water from deeper layers. The key diagnostic feature is the dominance and persistence of the primary root. Fibrous roots, in contrast, lack a single dominant main root. Therefore, the described pattern corresponds to a tap root system.
32. In many grasses, the primary root is short-lived and is replaced by a cluster of roots arising from the base of the stem. The origin of this root system is mainly:
ⓐ. Pericycle of the primary root
ⓑ. Root cap cells at the tip
ⓒ. Adventitious roots arising from stem tissues
ⓓ. Secondary growth from vascular cambium
Correct Answer: Adventitious roots arising from stem tissues
Explanation: In grasses and many other monocots, the radicle does not remain the dominant root for long; instead, numerous roots develop from the base of the stem. Because these roots arise from parts other than the radicle—most commonly the stem base—they are classified as adventitious in origin. When these adventitious roots occur in large numbers and are similar in size, they collectively form a fibrous root system. This arrangement increases absorption near the soil surface and provides strong anchorage over a wide area. The defining point is the stem-based origin rather than branching from a persistent primary root. Hence, the origin is adventitious roots arising from stem tissues.
33. Which pair correctly matches a plant group with its most typical root system pattern at the seedling-to-adult stage?
ⓐ. Monocots — persistent tap root with strong primary root dominance
ⓑ. Dicots — persistent tap root formed by continuation of the radicle
ⓒ. Dicots — fibrous roots formed exclusively from stem nodes
ⓓ. Monocots — tap root formed mainly from pericycle proliferation
Correct Answer: Dicots — persistent tap root formed by continuation of the radicle
Explanation: In most dicot plants, the embryonic radicle continues to grow after germination and becomes the primary root, forming a tap root system. This persistent main root then produces lateral branches, creating a clear hierarchy of primary, secondary, and tertiary roots. Monocots commonly show replacement of the primary root by many adventitious roots from the stem base, leading to a fibrous appearance rather than primary root dominance. The diagnostic criterion is whether the radicle persists as the main root axis. Therefore, the correct matching is dicots with a tap root system derived from the radicle.
34. A student is asked to identify an example of a fibrous root system. Which choice is the best example?
ⓐ. Mustard
ⓑ. Pea
ⓒ. Mango
ⓓ. Wheat
Correct Answer: Wheat
Explanation: Wheat is a typical monocot plant in which the primary root is soon replaced by numerous roots arising from the base of the stem. These roots are similar in size and spread out in the soil without a single dominant main root, producing the characteristic fibrous root system. This structure improves absorption from upper soil layers and provides strong anchorage, especially in loose soil. In contrast, mustard, pea, and mango are commonly cited as plants with tap roots where the primary root persists and branches laterally. The key distinction is the presence of many similar roots rather than one main root. Hence, wheat is the best example of a fibrous root system.
35. Which statement most accurately defines “adventitious roots” based on origin?
ⓐ. Roots that arise only from the radicle and persist throughout life
ⓑ. Roots that arise from organs other than the radicle, such as stem or leaves
ⓒ. Roots that arise only as lateral branches from the primary root
ⓓ. Roots that arise only after secondary growth begins in the root
Correct Answer: Roots that arise from organs other than the radicle, such as stem or leaves
Explanation: Adventitious roots are defined by their site of origin rather than their function or appearance. They develop from parts of the plant other than the radicle—commonly from stems (nodes, internodes, base) or even from leaves under certain conditions. This feature allows plants to adapt by forming supportive roots (like in banyan), climbing or clinging roots (like in ivy), or storage roots (like in sweet potato). The defining concept is that they are not direct continuations of the embryonic primary root. Because they can form in response to environmental or developmental cues, they are also important in vegetative propagation. Therefore, adventitious roots are roots arising from organs other than the radicle.
36. Sweet potato stores food in swollen roots that originate from the stem region rather than from the primary root. These storage roots are best classified as:
ⓐ. Tuberous adventitious roots
ⓑ. Fleshy tap roots
ⓒ. Pneumatophores
ⓓ. Parasitic haustorial roots
Correct Answer: Tuberous adventitious roots
Explanation: In sweet potato, the thickened storage structures are roots that arise adventitiously from the stem region and enlarge due to accumulation of reserve food. Because their origin is not the radicle-based primary root, they are not classified as tap roots. The term “tuberous adventitious roots” captures both the function (storage with swelling) and the origin (adventitious). This differs from carrot or radish where the primary tap root becomes fleshy for storage. The key diagnostic clue is stem-region origin followed by swelling. Hence, sweet potato shows tuberous adventitious roots.
37. A plant shows multiple roots emerging from the lower nodes of the stem and providing extra support, as seen in maize. These roots are best described as:
ⓐ. Tap roots with secondary branching
ⓑ. Respiratory roots for gaseous exchange
ⓒ. Stilt roots formed as adventitious roots from stem nodes
ⓓ. Storage roots formed by primary root thickening
Correct Answer: Stilt roots formed as adventitious roots from stem nodes
Explanation: In maize, additional roots develop from the lower nodes of the stem and grow obliquely into the soil, acting like supportive braces. Because they arise from stem nodes rather than the radicle, they are adventitious in origin. Their primary role is mechanical support, helping the plant remain upright against wind and lodging. This modification is specifically termed stilt roots, commonly associated with maize and sugarcane. The defining features are node-based origin and supportive function. Therefore, they are correctly identified as stilt roots formed as adventitious roots from stem nodes.
38. Which option correctly pairs a plant with a tap root modified mainly for storage?
ⓐ. Wheat — fibrous roots storing starch
ⓑ. Maize — stilt roots storing oils
ⓒ. Banyan — prop roots storing proteins
ⓓ. Carrot — conical tap root storing food
Correct Answer: Carrot — conical tap root storing food
Explanation: Carrot is a classic example where the primary tap root becomes fleshy and conical due to storage of reserve food materials. The storage involves enlargement of the main root axis, which is derived from the radicle, preserving the tap root identity. This differs from fibrous systems where many similar roots dominate, and from adventitious storage roots like sweet potato that arise from stems. The conical shape is characteristic of carrot among storage tap roots and is commonly used as an identification point in morphology questions. Because the modification is storage within the tap root itself, carrot fits precisely. Hence, carrot has a conical tap root modified for food storage.
39. A botanist notes that the dominant “main root” in a plant developed directly from the embryo’s radicle. Which inference is most accurate?
ⓐ. The plant initially developed a tap root system by origin
ⓑ. The plant must be a monocot with fibrous roots
ⓒ. The plant’s roots are necessarily adventitious by origin
ⓓ. The plant can form only prop roots throughout life
Correct Answer: The plant initially developed a tap root system by origin
Explanation: The radicle is the embryonic structure that gives rise to the primary root during germination. When the radicle persists and continues as the main root axis, the root system is classified as tap root by origin, regardless of later modifications. This foundational criterion separates tap roots (radicle-derived primary root dominance) from adventitious roots (arising from stem/leaf tissues) and from fibrous systems where the primary root is replaced by many similar roots. While some plants may later develop additional adventitious roots, the initial presence of a radicle-derived main root indicates tap root origin. This is a standard diagnostic inference used in morphology. Therefore, the most accurate inference is a tap root system by origin.
40. A teacher asks for the best example of adventitious roots used for climbing or attachment. Which is the most suitable example?
ⓐ. Mustard roots
ⓑ. Ivy roots
ⓒ. Radish roots
ⓓ. Gram roots
Correct Answer: Ivy roots
Explanation: Ivy develops adventitious roots from its stem that help it cling to and climb on vertical surfaces such as walls or tree trunks. These roots are not derived from the radicle, and their main role is attachment rather than absorption from soil. Such clinging roots enable the plant to gain height and access more light without investing heavily in a thick supporting stem. This is a common morphological adaptation in climbers and creepers. The defining feature is stem-based origin combined with attachment function. Hence, ivy is the most suitable example of adventitious roots used for climbing or attachment.
41. A storage tap root that is broad at the top and gradually tapers toward the lower end is termed:
ⓐ. Fusiform root
ⓑ. Napiform root
ⓒ. Conical root
ⓓ. Tuberous root
Correct Answer: Conical root
Explanation: A conical storage root shows maximum thickness near the upper region and then steadily narrows downwards like a cone. This form develops due to deposition of reserve food in the primary tap root, increasing its girth without losing the tapering pattern. Carrot is a standard example where the tap root becomes conical and fleshy for storage. The gradual taper distinguishes it from fusiform roots, which swell more in the middle, and from napiform roots, which look more top-heavy and abruptly narrow. Since the defining feature is broad top with gradual narrowing, conical root is the correct term.
42. Which plant is the most appropriate example of a conical storage tap root?
ⓐ. Carrot
ⓑ. Radish
ⓒ. Turnip
ⓓ. Sweet potato
Correct Answer: Carrot
Explanation: Carrot develops a fleshy storage organ mainly by thickening of the primary tap root, producing a characteristic conical shape. The upper portion is thicker and the diameter decreases progressively toward the tip, matching the conical definition. Radish typically shows fusiform swelling, and turnip commonly shows napiform form with a more rounded top and abrupt tapering. Sweet potato stores food in adventitious roots rather than a modified tap root, so it is not a tap-root storage example. Hence, carrot is the most appropriate example of a conical storage tap root.
43. A storage tap root that is swollen in the middle and tapers toward both the top and the bottom is best described as:
ⓐ. Conical
ⓑ. Napiform
ⓒ. Tuberous
ⓓ. Fusiform
Correct Answer: Fusiform
Explanation: Fusiform storage roots have a spindle-like outline, showing maximum swelling around the middle portion and tapering at both ends. This shape results from reserve food accumulation in the tap root, creating a thickened central region while retaining narrower ends. Radish is a commonly cited example that displays this fusiform form clearly. The key distinction from conical roots is that conical roots are thickest near the top, not in the middle. Napiform roots, in contrast, are more rounded at the top and then narrow abruptly. Therefore, the spindle-shaped middle swelling indicates a fusiform root.
44. Which plant is the best example of a fusiform storage tap root?
ⓐ. Carrot
ⓑ. Radish
ⓒ. Turnip
ⓓ. Maize
Correct Answer: Radish
Explanation: Radish develops a storage organ by thickening of the primary tap root, producing a fusiform (spindle-shaped) form. The root becomes thickest in the middle and then narrows toward both ends, which is the defining feature of fusiform roots. Carrot typically shows a conical pattern, while turnip is generally categorized as napiform with a more rounded upper swelling and abrupt tapering. Maize, being a monocot, commonly shows adventitious roots and does not form fusiform tap-root storage structures. Hence, radish is the best example of a fusiform storage tap root.
45. A storage root that becomes markedly swollen at the upper part, almost spherical, and then abruptly tapers into a thin tail-like end is termed:
ⓐ. Napiform root
ⓑ. Fusiform root
ⓒ. Conical root
ⓓ. Stilt root
Correct Answer: Napiform root
Explanation: Napiform storage roots show a pronounced swelling near the top that gives a rounded or turnip-like appearance, followed by a sudden narrowing into a slender lower portion. This happens due to heavy deposition of reserves in the upper region of the tap root, often involving adjacent upper root region in overall swelling. The abrupt taper distinguishes napiform roots from conical roots, which taper gradually, and from fusiform roots, which swell most in the middle. Stilt roots are supportive adventitious roots and are unrelated to storage shapes. Therefore, the described spherical-top with abrupt tapering matches a napiform root.
46. Which plant is most appropriately matched with a napiform storage root?
ⓐ. Radish
ⓑ. Carrot
ⓒ. Sweet potato
ⓓ. Turnip
Correct Answer: Turnip
Explanation: Turnip is a standard example of a napiform storage root, where the upper portion becomes prominently swollen and rounded while the lower portion narrows sharply. This morphology aligns with the napiform definition of a top-heavy swelling followed by an abrupt taper. Radish typically shows fusiform swelling concentrated in the middle, and carrot shows a conical taper that is more gradual. Sweet potato stores food in adventitious roots and is not used as a classic napiform tap-root example. Hence, turnip is the most appropriately matched plant with a napiform storage root.
47. In terms of the region of maximum swelling, which pairing is most accurate?
ⓐ. Fusiform—middle region thickest; Conical—upper region thickest
ⓑ. Conical—middle region thickest; Napiform—lower region thickest
ⓒ. Napiform—uniform thickness; Fusiform—upper region thickest
ⓓ. Conical—lower region thickest; Napiform—middle region thickest
Correct Answer: Fusiform—middle region thickest; Conical—upper region thickest
Explanation: Fusiform roots are spindle-shaped and therefore show their greatest girth in the middle portion, tapering toward both ends. Conical roots, on the other hand, are thickest near the upper part and gradually narrow toward the lower end. This difference in swelling distribution is a key diagnostic feature used in morphology questions. Napiform roots are thickest at the upper part but with a more rounded swelling and a more abrupt taper than conical roots. Because the statement correctly captures the hallmark swelling pattern for both fusiform and conical roots, it is the most accurate pairing.
48. A student finds a swollen edible underground structure and claims it is a “tuberous storage tap root.” Which observation would most strongly refute that claim and suggest an adventitious storage root instead?
ⓐ. It has lateral branches and a main axis
ⓑ. It shows root hairs near the tip
ⓒ. It arises clearly from the radicle region in seedlings
ⓓ. It develops from stem region and multiple similar swollen roots occur
Correct Answer: It develops from stem region and multiple similar swollen roots occur
Explanation: A storage tap root is defined by persistence and thickening of the radicle-derived primary root, usually showing a dominant main root axis. If the swollen roots originate from the stem region and occur as multiple similar swollen roots, the origin is adventitious rather than radicle-based. This pattern is typical of adventitious storage roots (such as in sweet potato), where several roots from stem tissue enlarge to store food. The site of origin is the most decisive criterion for distinguishing tap-root storage from adventitious storage. Therefore, development from the stem region with multiple similar swollen roots strongly refutes the “storage tap root” claim.
49. Which statement best captures why conical, fusiform, and napiform forms are grouped together under “storage tap roots”?
ⓐ. They arise from stem nodes and replace the primary root early
ⓑ. They are aerial roots specialized for support and attachment
ⓒ. They develop by thickening of radicle-derived primary root to store reserves
ⓓ. They are lateral roots that become swollen after secondary growth only
Correct Answer: They develop by thickening of radicle-derived primary root to store reserves
Explanation: Conical, fusiform, and napiform roots are all classic shapes produced when the primary tap root thickens due to reserve food accumulation. The defining point is origin from the radicle, which persists as the main root and becomes fleshy for storage. While shape and swelling distribution differ among these types, the shared basis is that the tap root itself is modified for storage. This distinguishes them from storage roots of adventitious origin (like sweet potato) and from supportive or respiratory root modifications. Because the core reason for grouping is radicle-derived thickening for reserve storage, that statement is correct.
50. Beetroot is commonly included with napiform storage roots in basic morphology classification because it typically shows:
ⓐ. A middle swelling tapering at both ends like a spindle
ⓑ. A rounded upper swelling with a distinctly tapering lower end
ⓒ. A gradual cone-like taper from top to bottom without abrupt narrowing
ⓓ. Numerous equal-sized roots arising from the stem base
Correct Answer: A rounded upper swelling with a distinctly tapering lower end
Explanation: Beetroot is often grouped with napiform storage roots because it commonly exhibits a pronounced swelling toward the upper region with a narrower lower continuation. This produces an overall turnip-like or top-heavy appearance, followed by a tapering end, which aligns with the napiform pattern used in standard morphology descriptions. The key distinction from fusiform is that fusiform roots swell mainly in the middle, and from conical roots is that conical tapering is more gradual and less top-rounded. It is also not a fibrous system, as it is discussed under storage forms of tap roots in basic classification. Therefore, the rounded upper swelling with a tapering lower end is the best match.
51. Prop roots are best described as roots that:
ⓐ. Arise from underground stems and store food reserves
ⓑ. Grow upward from soil for respiration in waterlogged conditions
ⓒ. Originate from aerial branches and grow down to provide pillar-like support
ⓓ. Develop as swollen tap roots with conical shape for storage
Correct Answer: Originate from aerial branches and grow down to provide pillar-like support
Explanation: Prop roots are adventitious roots that develop from aerial branches and extend downward into the soil, where they thicken and act as supportive pillars. This modification increases mechanical stability, allowing trees with extensive horizontal branching to spread without branches collapsing. The roots eventually become woody and function like additional trunks, distributing weight over a wider base. This is classically seen in banyan, where prop roots enable a broad canopy. The defining features are branch origin, downward growth, and support function. Hence, prop roots are roots from aerial branches that provide pillar-like support.
52. In maize, the supportive roots that arise from the lower stem nodes and enter the soil obliquely are called:
ⓐ. Prop roots
ⓑ. Stilt roots
ⓒ. Pneumatophores
ⓓ. Haustorial roots
Correct Answer: Stilt roots
Explanation: Stilt roots are adventitious roots that develop from the lower nodes of the stem and grow obliquely into the soil to provide extra support. In maize, these roots act like braces that help the plant remain upright, especially against wind and lodging. Their stem-node origin distinguishes them from tap root branches, and their supportive role differentiates them from respiratory roots or parasitic roots. This modification is common in certain tall grasses where the aerial shoot needs reinforcement at the base. Because the classic example is maize, the correct term is stilt roots. Therefore, maize shows stilt roots for support.
53. Which example is the most appropriate match for prop roots?
ⓐ. Banyan
ⓑ. Mangrove
ⓒ. Cuscuta
ⓓ. Carrot
Correct Answer: Banyan
Explanation: Banyan is a classic example of prop roots, where adventitious roots arise from aerial branches and grow down toward the soil. Once these roots reach the ground, they thicken and function as strong supportive pillars that help bear the weight of large, spreading branches. This adaptation allows the banyan to expand laterally over a wide area while maintaining structural stability. The feature is not primarily for respiration, parasitism, or storage; it is for mechanical support of the canopy. Because banyan demonstrates this modification prominently, it is the most appropriate match. Hence, banyan is the correct example for prop roots.
54. Buttress roots are best associated with which adaptive advantage?
ⓐ. Increasing oxygen uptake in swampy soil
ⓑ. Providing stability to tall trees by widening the base near the trunk
ⓒ. Absorbing atmospheric moisture in epiphytic habitats
ⓓ. Storing large amounts of starch in the primary root
Correct Answer: Providing stability to tall trees by widening the base near the trunk
Explanation: Buttress roots are large, plank-like extensions at the base of the trunk that spread outward and partially above the ground. They increase the surface area of anchorage and distribute mechanical stress, helping tall trees remain stable, especially in shallow or nutrient-poor soils where deep roots may not develop effectively. This adaptation is common in many large tropical rainforest trees that face strong winds and heavy canopy loads. The structural design supports the trunk like supportive flanges, reducing the risk of toppling. Because the key advantage is mechanical stability through a widened base, this option is correct. Therefore, buttress roots provide stability by widening the trunk base.
55. A student confuses prop roots and stilt roots. Which statement best distinguishes them?
ⓐ. Prop roots arise from leaves, while stilt roots arise from root hairs
ⓑ. Prop roots arise from aerial branches, while stilt roots arise from lower stem nodes
ⓒ. Prop roots occur only in monocots, while stilt roots occur only in dicots
ⓓ. Prop roots are respiratory, while stilt roots are storage modifications
Correct Answer: Prop roots arise from aerial branches, while stilt roots arise from lower stem nodes
Explanation: Prop roots develop from aerial branches and grow downward into the soil, often forming pillar-like supports as seen in banyan. Stilt roots, in contrast, arise from the lower stem nodes near the base of the plant and grow obliquely into the soil, acting as braces, as seen in maize and sugarcane. Both are supportive and both are adventitious in origin, but their points of origin differ clearly. This distinction is central to identifying them in morphology questions. Because location of origin is the most reliable separator, the statement comparing branch versus lower node origin is correct. Hence, prop roots come from aerial branches, while stilt roots come from lower stem nodes.
56. Which scenario most strongly suggests buttress roots rather than prop or stilt roots?
ⓐ. Multiple thin roots hang from branches and later become pillar-like after touching soil
ⓑ. Several roots emerge from lower nodes and enter soil at an angle to brace the stem
ⓒ. Broad, plate-like root extensions radiate from the trunk base above ground level
ⓓ. Upward-growing roots with pores project from muddy soil around the plant
Correct Answer: Broad, plate-like root extensions radiate from the trunk base above ground level
Explanation: Buttress roots are characterized by large, flattened, plank-like extensions that emerge from the base of the trunk and spread outward, often visible above the ground. Their main role is to stabilize tall trees by increasing the effective base width and providing strong anchorage in shallow soils. This is distinct from prop roots, which descend from branches, and stilt roots, which emerge from lower stem nodes as braces. The described broad, plate-like radiating structures match the classic buttress form rather than pillar-like or angled brace roots. Such roots are especially common in large tropical trees. Therefore, broad plate-like root extensions at the trunk base indicate buttress roots.
57. Supportive adventitious roots in sugarcane that arise from basal nodes are functionally similar to maize stilt roots. They are primarily meant to:
ⓐ. Increase surface area for absorption by forming root hairs
ⓑ. Prevent lodging by providing extra mechanical support to the stem
ⓒ. Absorb oxygen directly from air in waterlogged habitats
ⓓ. Store reserve food as swollen underground structures
Correct Answer: Prevent lodging by providing extra mechanical support to the stem
Explanation: In tall, grass-like plants such as sugarcane, additional adventitious roots arise from basal stem nodes and penetrate the soil to strengthen anchorage. Their primary function is mechanical support, helping the plant resist bending or falling (lodging) due to wind, rain, or heavy aerial parts. These roots act like braces, increasing stability at the base rather than specializing for storage or respiration. While they may also absorb water and minerals, their adaptive significance in this context is support. This is the same supportive concept as stilt roots in maize. Hence, the main purpose is to prevent lodging by providing extra mechanical support.
58. Which statement correctly identifies the origin category of prop roots, stilt roots, and buttress roots?
ⓐ. All are modified lateral roots arising only from the pericycle
ⓑ. All are modified tap roots formed by thickening of the primary root
ⓒ. All are modified adventitious roots that enhance mechanical support
ⓓ. All are modified root hairs that become woody at maturity
Correct Answer: All are modified adventitious roots that enhance mechanical support
Explanation: Prop roots, stilt roots, and buttress roots are all support-related root modifications that generally develop from parts other than the radicle-derived primary root. Because they arise from stems or branches (or the trunk base region) and not as simple branches of the primary root axis, they are classified as adventitious in origin. Their common functional theme is providing mechanical stability—prop roots act as pillars, stilt roots act as braces, and buttress roots broaden the base. This shared adaptive role makes them a cohesive group under supportive modifications. They are not root hairs and are not primarily storage forms. Therefore, they are best identified as modified adventitious roots enhancing support.
59. A banyan tree spreads widely and continues to expand its canopy. The main mechanical advantage provided by prop roots is that they:
ⓐ. Reduce transpiration by forming a thick cuticle around roots
ⓑ. Increase the number of leaves by inducing branching at nodes
ⓒ. Provide additional points of anchorage and load-bearing support under heavy branches
ⓓ. Convert atmospheric nitrogen into ammonia through symbiotic bacteria
Correct Answer: Provide additional points of anchorage and load-bearing support under heavy branches
Explanation: Prop roots in banyan descend from branches and, after reaching the soil, thicken into strong, woody supports. This creates multiple supplementary “trunk-like” pillars that share the weight of massive horizontal branches. By increasing the number of ground contact points, the tree gains improved stability and can expand laterally without structural failure. This adaptation is mechanical rather than physiological processes like nitrogen fixation or transpiration control. The load distribution across many supports allows the canopy to grow larger and spread farther. Hence, prop roots provide additional anchorage and load-bearing support under heavy branches.
60. Which plant type is most likely to show prominent buttress roots as a common field observation?
ⓐ. Tall rainforest tree growing in shallow soil layers
ⓑ. Desert cactus with thick cuticle and reduced leaves
ⓒ. Submerged aquatic plant with flexible stems
ⓓ. Short grass growing in loose topsoil
Correct Answer: Tall rainforest tree growing in shallow soil layers
Explanation: Buttress roots are commonly seen in large tropical rainforest trees that grow rapidly and reach great heights while often rooting in shallow, nutrient-rich surface layers. In such habitats, deep rooting may be limited, and the heavy canopy plus wind exposure creates a risk of toppling. Buttress roots provide broad, plank-like supports at the base, increasing stability by widening the effective trunk base and distributing mechanical forces. This modification is therefore strongly associated with tall trees in tropical forests rather than aquatic plants, grasses, or desert cacti. The characteristic visibility of these root flanges above ground makes them a common field feature in rainforests. Hence, tall rainforest trees in shallow soils are most likely to show prominent buttress roots.
61. Pneumatophores are most likely to be observed in plants growing in:
ⓐ. Waterlogged, oxygen-poor soils where normal roots face low aeration
ⓑ. Rocky deserts where water storage is the main challenge
ⓒ. Alpine regions where freezing prevents root activity for months
ⓓ. Deep forest soils where humus is abundant and loose
Correct Answer: Waterlogged, oxygen-poor soils where normal roots face low aeration
Explanation: Pneumatophores are specialized respiratory roots that develop when the soil is saturated with water and becomes deficient in oxygen. In such anaerobic conditions, underground roots cannot get enough oxygen for aerobic respiration. Pneumatophores grow upward above the soil or water surface, enabling direct gaseous exchange with the atmosphere. They commonly bear openings (lenticels) that facilitate oxygen intake and carbon dioxide release. This adaptation is especially useful in marshy, swampy, or tidal habitats. Therefore, waterlogged and oxygen-poor soils are the typical conditions where pneumatophores are found.
62. A key structural feature that enables pneumatophores to exchange gases efficiently is the presence of:
ⓐ. Stomata-like pores that open and close rhythmically
ⓑ. A thick cuticle that prevents any gas movement
ⓒ. Lenticels (aeration pores) on the exposed root surface
ⓓ. Root hairs that absorb oxygen dissolved in soil water
Correct Answer: Lenticels (aeration pores) on the exposed root surface
Explanation: Pneumatophores function as respiratory roots by allowing gaseous exchange between internal tissues and the external atmosphere. The exposed portions of these roots commonly bear lenticels, which are specialized aeration pores facilitating diffusion of gases. Through these pores, oxygen enters and supports aerobic respiration in submerged root tissues, while carbon dioxide diffuses out. This mechanism is crucial where soil air spaces are filled with water and diffusion of oxygen through soil is severely reduced. The adaptation is structural and continuous, not dependent on rhythmic opening and closing like stomata. Hence, lenticels on the exposed surface are the key feature enabling efficient gas exchange.
63. Which plant is the most appropriate example where pneumatophores are commonly developed?
ⓐ. Wheat
ⓑ. Carrot
ⓒ. Pea
ⓓ. Mangrove plants in marshy coastal habitats
Correct Answer: Mangrove plants in marshy coastal habitats
Explanation: Pneumatophores are a classic adaptation of plants growing in swampy, marshy, or tidal coastal areas where soil is waterlogged and oxygen availability is low. Mangrove plants frequently develop these upward-growing respiratory roots to access atmospheric oxygen. The pneumatophores project above the mud or water surface and contain aeration structures that support gas diffusion. This adaptation is strongly associated with coastal wetland ecosystems and is often used as an identifying feature of mangrove vegetation. In contrast, wheat, carrot, and pea typically grow in well-aerated soils and do not require such respiratory roots. Therefore, mangrove plants in marshy coastal habitats are the correct example.
64. The most accurate functional statement about pneumatophores is that they primarily help in:
ⓐ. Storing reserve food to survive drought
ⓑ. Facilitating respiration by improving oxygen supply to submerged root tissues
ⓒ. Absorbing atmospheric moisture in epiphytic conditions
ⓓ. Providing climbing support by attaching to surfaces
Correct Answer: Facilitating respiration by improving oxygen supply to submerged root tissues
Explanation: In waterlogged soils, oxygen diffusion is slow because air spaces are replaced by water, making aerobic respiration difficult for underground roots. Pneumatophores develop as specialized roots that grow upward into the air, where oxygen is readily available. They allow oxygen to diffuse inward and reach internal tissues that otherwise suffer from oxygen deficiency. This supports energy production via aerobic pathways, enabling normal root functioning in anaerobic substrates. Their morphology is therefore primarily linked to gas exchange, not storage, attachment, or moisture absorption. Hence, their main role is facilitating respiration by improving oxygen supply.
65. Haustoria are best defined as specialized structures in parasitic plants that:
ⓐ. Penetrate host tissues to obtain water and nutrients directly from the host
ⓑ. Increase soil absorption by forming extra root hairs in dry conditions
ⓒ. Enhance mechanical support by forming pillar-like roots from branches
ⓓ. Enable gaseous exchange by growing upward with aeration pores
Correct Answer: Penetrate host tissues to obtain water and nutrients directly from the host
Explanation: Haustoria are specialized invasive organs developed by parasitic plants to establish a physiological connection with the host. They penetrate host tissues and connect with conducting elements, enabling the parasite to draw water, minerals, and often organic nutrients. This direct tapping allows parasitic plants to survive even when their own absorptive capacity is reduced or absent. The structure is adapted for attachment and internal access rather than for soil absorption or support. Because the central concept is host penetration and nutrient withdrawal, haustoria are a hallmark of plant parasitism. Therefore, haustoria are correctly defined as penetrating structures that obtain resources from the host.
66. Which example most strongly represents a parasitic plant commonly associated with haustoria?
ⓐ. Cuscuta (dodder) twining on host plants
ⓑ. Banyan producing hanging roots from branches
ⓒ. Mangrove producing upward-growing respiratory roots
ⓓ. Maize producing brace-like roots from stem nodes
Correct Answer: Cuscuta (dodder) twining on host plants
Explanation: Cuscuta is a well-known parasitic plant that lacks effective independent nutrition and depends on a host for sustenance. It forms haustoria that penetrate the host tissues, establishing connections to extract water and nutrients. The plant typically twines around host stems, increasing contact points for haustorial development. This parasitic strategy is distinct from supportive root modifications (like banyan or maize) or respiratory adaptations (like mangroves). The key indicator is nutritional dependence achieved through host penetration. Hence, Cuscuta twining on host plants is the strongest example linked with haustoria.
67. In many stem parasites, haustoria are most directly important because they allow the parasite to:
ⓐ. Fix atmospheric nitrogen in root nodules
ⓑ. Access the host’s conducting tissues for resource withdrawal
ⓒ. Perform photosynthesis more efficiently by increasing leaf area
ⓓ. Store starch in the parasite’s primary tap root
Correct Answer: Access the host’s conducting tissues for resource withdrawal
Explanation: The success of a parasitic plant depends on its ability to obtain essential resources from the host plant. Haustoria function by penetrating host tissues and establishing contact with conducting pathways, enabling transfer of water, minerals, and often organic solutes. This connection reduces the parasite’s dependence on soil-based absorption and can allow rapid growth even with limited root development. The adaptation is fundamentally about host exploitation rather than independent synthesis or storage. Because transport access is the core physiological benefit, the best description is access to the host’s conducting tissues. Therefore, haustoria are crucial for connecting to host transport systems for resource withdrawal.
68. A student says “pneumatophores and haustoria are both mainly for absorption from soil.” The best correction is:
ⓐ. Both are mainly storage roots, not absorptive structures
ⓑ. Pneumatophores are for attachment, haustoria are for support
ⓒ. Pneumatophores are for respiration, while haustoria obtain resources from a host plant
ⓓ. Both are primarily for increasing surface area via root hairs
Correct Answer: Pneumatophores are for respiration, while haustoria obtain resources from a host plant
Explanation: Pneumatophores develop when soil oxygen is limiting, so their primary role is to enable respiration by allowing gaseous exchange with the atmosphere. Haustoria, in contrast, are parasitic organs that penetrate host tissues to withdraw water and nutrients, often bypassing normal soil absorption requirements. These two modifications arise under different ecological pressures: low aeration for pneumatophores and nutritional dependence for haustoria. Neither is correctly described as “mainly absorbing from soil,” because pneumatophores are about gas exchange and haustoria are about host tapping. The functional distinction is central to understanding root modifications. Hence, pneumatophores are respiratory, while haustoria are host-resource extracting structures.
69. In a coastal swamp plant, upward-growing pencil-like roots projecting above the mud are most likely:
ⓐ. Pneumatophores adapted for gas exchange in anaerobic soil
ⓑ. Stilt roots adapted mainly to brace the stem against wind
ⓒ. Prop roots adapted to support spreading branches like pillars
ⓓ. Tuberous roots adapted for food storage in the soil
Correct Answer: Pneumatophores adapted for gas exchange in anaerobic soil
Explanation: Pencil-like roots projecting above muddy, waterlogged substrates are a classic external sign of respiratory roots. In anaerobic swamp soils, underground roots struggle to obtain oxygen, so these specialized roots grow upward to access atmospheric oxygen. Their exposed surfaces commonly contain aeration pores that allow diffusion of gases into internal tissues. This adaptation is strongly associated with coastal swamps and marshes where tidal waterlogging is frequent. The described form and habitat align with respiration rather than support or storage. Therefore, such upward pencil-like roots are most likely pneumatophores for gas exchange.
70. Which statement best reflects a key ecological advantage of haustorial parasitism?
ⓐ. It allows plants to survive only by increasing root hair density in dry soil
ⓑ. It eliminates the need for any contact with other plants
ⓒ. It enables a parasite to obtain resources even when soil nutrients or its own roots are insufficient
ⓓ. It ensures respiration in flooded habitats by producing aeration pores
Correct Answer: It enables a parasite to obtain resources even when soil nutrients or its own roots are insufficient
Explanation: Haustorial parasitism allows a plant to tap directly into a host’s resource stream, providing access to water, minerals, and often organic nutrients. This strategy can be advantageous when the parasite has reduced absorptive capability or grows in environments where independent acquisition is difficult. By connecting to host tissues, the parasite can maintain growth and reproduction with limited reliance on soil nutrient availability. The advantage is therefore nutritional and physiological, rooted in host dependence rather than enhanced soil absorption. This relationship can significantly increase survival prospects for the parasite in competitive habitats. Hence, haustoria provide an ecological advantage by enabling resource acquisition even when soil nutrients or the parasite’s own roots are insufficient.
71. In leguminous root nodules, the most direct benefit to the plant is the:
ⓐ. Increased transpiration due to larger root surface
ⓑ. Faster secondary growth due to cambial stimulation
ⓒ. Direct absorption of atmospheric oxygen by root hairs
ⓓ. Conversion of atmospheric nitrogen into usable nitrogenous forms
Correct Answer: Conversion of atmospheric nitrogen into usable nitrogenous forms
Explanation: Root nodules in many legumes house symbiotic nitrogen-fixing bacteria that can reduce atmospheric nitrogen into forms the plant can assimilate for making amino acids and proteins. This is especially valuable because atmospheric nitrogen is abundant but not directly usable by most plants. The association improves the plant’s nitrogen nutrition without relying solely on soil nitrates or ammonium. The plant, in return, supplies carbohydrates and a protected habitat to the bacteria. This mutual exchange enhances growth in nitrogen-poor soils and supports higher protein synthesis. Therefore, the key direct benefit is conversion of atmospheric nitrogen into usable nitrogenous forms.
72. A farmer observes better growth of legume seedlings after adding a specific bacterial culture to soil. The culture most likely promotes:
ⓐ. Formation of effective root nodules that enhance nitrogen fixation
ⓑ. Development of thicker cuticle on roots to prevent water loss
ⓒ. Production of pneumatophores to increase root respiration
ⓓ. Swelling of tap roots into conical storage organs
Correct Answer: Formation of effective root nodules that enhance nitrogen fixation
Explanation: Certain soil bacteria establish a symbiotic association with legume roots and stimulate the development of nodules where nitrogen fixation occurs. When an effective culture is introduced, the likelihood of successful colonization increases, improving nitrogen availability to the plant. This directly supports synthesis of chlorophyll, enzymes, and proteins, resulting in stronger vegetative growth. The interaction is mutualistic: bacteria gain food and shelter, while the plant gains a nitrogen source. This is why inoculated legumes often perform better in soils lacking suitable native strains. Hence, the culture most likely promotes effective nodule formation and nitrogen fixation.
73. The symbiotic association between a fungus and roots that improves phosphate uptake is called:
ⓐ. Lenticel association
ⓑ. Rhizosphere coupling
ⓒ. Mycorrhiza
ⓓ. Haustorial linkage
Correct Answer: Mycorrhiza
Explanation: Mycorrhiza is a mutualistic relationship in which fungal hyphae associate with plant roots and extend the effective absorptive area into the soil. This enhanced reach particularly improves uptake of relatively immobile nutrients like phosphates, and often also supports better water absorption. In exchange, the fungus receives organic carbon compounds from the plant’s photosynthate supply. The association can improve plant vigor, drought tolerance, and resistance to certain root pathogens. It is widely present across many flowering plants and is ecologically important in nutrient cycling. Therefore, the correct term is mycorrhiza.
74. Compared to root hairs alone, mycorrhizal hyphae are especially effective because they:
ⓐ. Replace xylem vessels and transport sugars upward
ⓑ. Spread through fine soil pores, increasing absorptive reach beyond the root surface
ⓒ. Convert atmospheric nitrogen directly into nitrate without microbes
ⓓ. Form woody prop roots that support heavy branches
Correct Answer: Spread through fine soil pores, increasing absorptive reach beyond the root surface
Explanation: Mycorrhizal hyphae form a fine network that can penetrate tiny soil pores not easily accessed by thicker root tissues. This substantially increases the soil volume explored for water and minerals, improving nutrient capture efficiency. The advantage is especially pronounced for nutrients like phosphate that diffuse slowly and are often depleted near the root surface. By extending the effective root system, hyphae increase contact with nutrient-rich microzones in the soil. In return, the plant supplies the fungus with carbohydrates, maintaining the mutualistic exchange. Thus, their key effectiveness comes from expanded absorptive reach through fine soil pores.
75. Root nodules are most specifically associated with which type of symbiosis?
ⓐ. Mutualism between nitrogen-fixing bacteria and legume roots
ⓑ. Parasitism where roots penetrate host vascular tissues
ⓒ. Commensalism where fungi attach without nutrient exchange
ⓓ. Predation where roots capture and digest insects
Correct Answer: Mutualism between nitrogen-fixing bacteria and legume roots
Explanation: Root nodules represent a mutualistic relationship in which bacteria live within specialized root structures and provide fixed nitrogen to the host plant. The plant benefits by obtaining nitrogen for protein and nucleic acid synthesis, often improving growth in low-nitrogen environments. The bacteria benefit by receiving carbohydrates and a stable, protected microenvironment within the nodule. This reciprocal exchange is central to the definition of mutualism. The structure and function of nodules are therefore tightly linked to bacterial nitrogen fixation rather than host exploitation. Hence, nodules are most specifically associated with mutualism between nitrogen-fixing bacteria and legume roots.
76. A key functional reason nodules maintain controlled oxygen levels is to:
ⓐ. Prevent mineral absorption from the soil solution
ⓑ. Increase transpiration pull through the xylem
ⓒ. Stop root hair formation in the maturation zone
ⓓ. Protect nitrogen-fixation enzymes that are sensitive to high oxygen
Correct Answer: Protect nitrogen-fixation enzymes that are sensitive to high oxygen
Explanation: Nitrogen fixation depends on enzyme systems that are inhibited or damaged when oxygen levels are too high. Yet, bacterial and plant cells still need oxygen for respiration to generate energy for the fixation process. Nodules therefore regulate oxygen availability so respiration can continue without inactivating nitrogen-fixation enzymes. This controlled environment allows efficient conversion of atmospheric nitrogen into plant-usable forms. The balance is crucial: too little oxygen limits energy supply, while too much harms fixation capacity. Thus, the core reason for oxygen control is protection of oxygen-sensitive nitrogen-fixation enzymes.
77. A non-leguminous plant shows markedly improved growth in phosphate-poor soil when associated with a fungus. The most likely explanation is:
ⓐ. The fungus produces root caps that protect the meristem
ⓑ. The fungus increases phosphate acquisition via a mycorrhizal association
ⓒ. The fungus induces formation of stilt roots for mechanical support
ⓓ. The fungus converts nitrate into nitrogen gas for faster uptake
Correct Answer: The fungus increases phosphate acquisition via a mycorrhizal association
Explanation: In phosphate-poor soils, plant growth is often limited because phosphate ions are relatively immobile and quickly depleted near roots. A mycorrhizal fungus extends hyphae into a larger soil volume, improving access to phosphate beyond the depletion zone. This enhanced uptake supports ATP formation, nucleic acid synthesis, and membrane development, which directly boosts growth. The plant supplies carbohydrates to the fungus, maintaining the mutualistic relationship. This mechanism is well-known across many flowering plants and is not restricted to legumes. Therefore, improved growth is best explained by increased phosphate acquisition via mycorrhiza.
78. Which pair is correctly matched as a symbiotic root modification and its principal outcome?
ⓐ. Haustoria — improved oxygen uptake in marshy soils
ⓑ. Pneumatophores — extraction of sugars from host tissues
ⓒ. Mycorrhiza — improved mineral uptake, especially phosphates
ⓓ. Prop roots — conversion of atmospheric nitrogen into ammonia
Correct Answer: Mycorrhiza — improved mineral uptake, especially phosphates
Explanation: Mycorrhiza is a symbiotic association where fungal hyphae collaborate with roots to improve absorption of water and minerals. The most emphasized mineral benefit is enhanced phosphate uptake because fungal hyphae explore soil microspaces efficiently. This supports plant metabolism, growth, and often stress tolerance, while the fungus receives organic carbon from the plant. The relationship is mutualistic and widespread among flowering plants. It is distinct from respiratory adaptations like pneumatophores and parasitic structures like haustoria. Hence, the correct match is mycorrhiza with improved mineral uptake, especially phosphates.
79. If a legume is grown in nitrogen-poor soil but fails to form nodules, the most likely immediate nutritional limitation is:
ⓐ. Reduced availability of usable nitrogen for amino acid and protein synthesis
ⓑ. Reduced uptake of carbon dioxide from air due to fewer stomata
ⓒ. Reduced light absorption because chlorophyll cannot bind magnesium
ⓓ. Reduced water absorption because root cap cells cannot secrete mucilage
Correct Answer: Reduced availability of usable nitrogen for amino acid and protein synthesis
Explanation: Nodules provide a biological route for converting atmospheric nitrogen into forms that plants can incorporate into amino acids and proteins. Without nodules, the plant must depend entirely on available soil nitrogen, which may be insufficient in nitrogen-poor conditions. This quickly constrains synthesis of proteins, enzymes, and nucleic acids, slowing growth and affecting overall vigor. While other nutrients matter, nitrogen is often the first limiting factor in such soils for legumes that normally benefit from fixation. The absence of nodulation therefore leads to a direct nitrogen nutrition shortfall. Hence, the immediate limitation is reduced usable nitrogen for amino acid and protein synthesis.
80. Which statement best distinguishes mycorrhiza from bacterial root nodules?
ⓐ. Mycorrhiza is always harmful, while nodules are always beneficial
ⓑ. Mycorrhiza mainly improves mineral/water uptake, while nodules mainly improve nitrogen supply via fixation
ⓒ. Mycorrhiza occurs only in legumes, while nodules occur only in non-legumes
ⓓ. Mycorrhiza forms in aerial roots, while nodules form only in leaves
Correct Answer: Mycorrhiza mainly improves mineral/water uptake, while nodules mainly improve nitrogen supply via fixation
Explanation: Mycorrhiza involves fungi that extend the root’s absorptive capacity, commonly enhancing phosphate and water uptake and improving stress resilience. Bacterial root nodules, in contrast, are specialized structures where nitrogen-fixing bacteria provide fixed nitrogen, directly supporting protein and nucleic acid synthesis. Both are mutualistic, but their principal contributions differ in the nutrient they most directly improve. The distinction is functional rather than limited to a single plant group or organ location. This conceptual separation is frequently tested because students often mix “better uptake” with “nitrogen fixation.” Therefore, mycorrhiza mainly improves mineral/water uptake, while nodules mainly improve nitrogen supply via fixation.
81. In a typical flowering plant stem, a “node” is best defined as the region where:
ⓐ. Leaves and axillary buds are borne on the stem
ⓑ. The stem shows maximum secondary thickening only
ⓒ. Root hairs emerge for water absorption
ⓓ. Xylem vessels are absent and only phloem is present
Correct Answer: Leaves and axillary buds are borne on the stem
Explanation: A node is the part of the stem that serves as the attachment point for leaves and commonly bears an axillary bud in the angle between the leaf and the stem. Because nodes are the sites where lateral organs arise, they are crucial for branching patterns and leaf arrangement. The presence of axillary buds at nodes enables the formation of lateral shoots, flowers, or inflorescences depending on the plant and season. This structural role also makes nodes key landmarks in identifying stem segments. Internodes lie between nodes and lack leaf attachment points. Therefore, the defining feature of a node is bearing leaves and axillary buds.
82. The “internode” of a stem refers to the:
ⓐ. Terminal bud at the shoot tip
ⓑ. Leaf base that wraps around the stem
ⓒ. Region where adventitious roots originate
ⓓ. Stem segment between two successive nodes
Correct Answer: Stem segment between two successive nodes
Explanation: An internode is the portion of the stem located between two adjacent nodes, and it largely contributes to elongation of the shoot. Since nodes are the sites of leaf and bud attachment, the internode is identified by the absence of such attachments along its length. Changes in internode length strongly influence plant height and spacing of leaves and branches. In many plants, rapid elongation during growth phases occurs mainly through internodal expansion. This concept is widely tested because students often confuse nodes with internodes in diagrams. Hence, the internode is correctly defined as the stem segment between two successive nodes.
83. An axillary bud is typically located:
ⓐ. At the root tip beneath the root cap
ⓑ. In the axil of a leaf at the node
ⓒ. Along the middle of an internode without any leaf nearby
ⓓ. Inside the xylem to regulate water movement
Correct Answer: In the axil of a leaf at the node
Explanation: The axillary bud develops in the angle (axil) formed between a leaf and the stem, which is anatomically associated with the node. This position is significant because axillary buds are the usual source of lateral branches, flowers, or inflorescences depending on developmental signals. Their presence at nodes explains why branching commonly originates from nodal regions rather than random points on internodes. Buds remain dormant or grow out based on hormonal control and environmental cues. Recognizing the axillary position is a standard morphology skill in practical identification. Therefore, an axillary bud is located in the leaf axil at the node.
84. The terminal (apical) bud primarily contributes to:
ⓐ. Lateral branch formation at each node
ⓑ. Formation of root hairs for absorption
ⓒ. Increase in stem length through primary growth
ⓓ. Storage of reserve food in the cortex only
Correct Answer: Increase in stem length through primary growth
Explanation: The terminal bud contains the shoot apical meristem, which is responsible for primary growth that increases the length of the stem. Continuous cell division and differentiation at this meristem produce new stem tissues, leaves, and new nodes and internodes as the shoot extends. This is why removal of the terminal bud can reduce vertical elongation and alter plant architecture. While lateral branches arise from axillary buds, the main upward extension is chiefly governed by the apical bud. This concept links structure with growth pattern in a directly testable way. Hence, the terminal bud primarily drives increase in stem length via primary growth.
85. One major functional advantage of having distinct nodes and internodes in a stem is that it:
ⓐ. Allows organized placement of leaves and buds for efficient branching and light capture
ⓑ. Prevents all lateral growth by permanently suppressing buds
ⓒ. Ensures that water moves only downward in the plant body
ⓓ. Eliminates the need for vascular tissues in the stem
Correct Answer: Allows organized placement of leaves and buds for efficient branching and light capture
Explanation: Nodes act as structured points for leaf attachment and bud placement, while internodes provide spacing between these points, creating a predictable architectural pattern. This organization supports efficient display of leaves for light interception and allows controlled branching through axillary bud outgrowth. By adjusting internode length, plants can optimize spacing of leaves and branches to reduce self-shading. The node–internode pattern also makes it easier to distribute reproductive structures at suitable positions. This structural plan is a core feature of stems that connects directly to plant form and function. Therefore, distinct nodes and internodes enable organized leaf and bud placement for effective branching and light capture.
86. When the apical bud is removed, many plants show increased growth of axillary buds mainly due to reduced:
ⓐ. Mineral absorption by root hairs
ⓑ. Lenticel formation in the stem surface
ⓒ. Apical dominance controlled by the shoot tip
ⓓ. Secondary thickening by vascular cambium
Correct Answer: Apical dominance controlled by the shoot tip
Explanation: Apical dominance refers to the inhibitory effect of the shoot apex on the growth of axillary buds, leading to stronger upward growth and limited lateral branching. When the apical bud is removed, the suppressive influence decreases and axillary buds are more likely to grow out into lateral branches. This shift changes plant architecture from a single dominant axis to a bushier form. The phenomenon is widely used in horticulture to promote branching and increase yield in certain crops. It is directly tied to the functional role of buds at nodes. Hence, removal of the apical bud increases axillary bud growth by reducing apical dominance.
87. A bud that develops at an unusual position such as on an internode or on older stem tissue (not in the leaf axil) is best termed:
ⓐ. Terminal bud
ⓑ. Axillary bud
ⓒ. Floral bud
ⓓ. Adventitious bud
Correct Answer: Adventitious bud
Explanation: Adventitious buds arise from locations other than the typical axillary position at nodes, such as internodes, older stems, roots, or even leaves. Their development is important for regeneration, vegetative propagation, and recovery after injury. Because they do not originate in the standard leaf axil, they are considered “adventitious” with respect to position. This concept helps explain how some plants sprout new shoots from cut stems or damaged regions. It is also frequently tested by presenting scenarios involving shoot emergence from unexpected places. Therefore, a bud forming on an internode or older stem tissue is an adventitious bud.
88. Which statement correctly links internode length with a visible growth outcome?
ⓐ. Longer internodes always reduce plant height and keep stems compact
ⓑ. Shorter internodes produce a compact plant with leaves and nodes closer together
ⓒ. Internode length has no effect on spacing of leaves and branches
ⓓ. Internodes determine only root branching patterns, not shoot architecture
Correct Answer: Shorter internodes produce a compact plant with leaves and nodes closer together
Explanation: Internode length determines the spacing between successive nodes, and nodes carry leaves and axillary buds. When internodes are short, nodes are closer, resulting in a compact appearance with reduced distance between leaves and potential branches. Conversely, longer internodes increase spacing and often contribute to a taller, more spaced-out shoot. This relationship is commonly assessed through plant habit descriptions such as “rosette” or “elongated” growth forms. Because internodes directly set node-to-node distance, they strongly influence overall shoot architecture. Hence, shorter internodes lead to a compact plant with closely spaced leaves and nodes.
89. A practical field clue that confirms a structure is a stem (not a root) is the presence of:
ⓐ. Root cap and root hair zone at the tip
ⓑ. Endodermis with Casparian strips visible externally
ⓒ. Pneumatophores projecting above water
ⓓ. Nodes bearing leaves and buds along the axis
Correct Answer: Nodes bearing leaves and buds along the axis
Explanation: Stems are characterized by nodes and internodes, and nodes typically bear leaves, buds, or scars of these structures. This nodal organization is a reliable external marker that distinguishes stems from roots in field identification. Roots lack nodes and do not bear leaves or buds in the typical shoot pattern. The presence of buds, especially axillary buds at nodes, further confirms shoot identity and future branching capacity. Since this feature is visible without anatomical sectioning, it is a practical diagnostic tool. Therefore, nodes bearing leaves and buds along the axis confirm the structure is a stem.
90. The protective role of bud scales (when present) is mainly to:
ⓐ. Increase photosynthesis by exposing chlorophyll-rich tissues
ⓑ. Conduct water upward through specialized pores
ⓒ. Shield the delicate meristematic tissues from desiccation and mechanical injury
ⓓ. Convert atmospheric nitrogen into usable compounds for the bud
Correct Answer: Shield the delicate meristematic tissues from desiccation and mechanical injury
Explanation: Bud scales are modified protective structures that cover buds and help safeguard the developing meristem and young leaf primordia. They reduce water loss by limiting exposure to dry air and also protect against physical damage, especially during unfavorable seasons. This protection is important because the tissues inside buds are tender and actively dividing, making them vulnerable to injury. In many plants, bud scales also help the bud survive cold or dry periods until conditions become favorable for growth. The function is therefore defensive rather than conductive or nutritional conversion, and it supports bud survival and future shoot development. Hence, bud scales primarily shield delicate meristematic tissues from desiccation and mechanical injury.
91. A horizontal underground stem with distinct nodes, internodes, scale leaves, and axillary buds, often used for vegetative propagation, is best identified as a:
ⓐ. Rhizome
ⓑ. Bulb
ⓒ. Corm
ⓓ. Tap root
Correct Answer: Rhizome
Explanation: A rhizome is an underground stem that grows horizontally and shows clear stem characters such as nodes, internodes, scale leaves, and buds. These buds can give rise to aerial shoots, making rhizomes important for perennation and vegetative propagation. The presence of nodes and buds distinguishes it from true roots, while its horizontal growth and scaly leaf remnants are typical identification traits. Rhizomes also store food reserves, helping the plant survive unfavorable seasons and regrow. This structure is common in several perennials and is frequently tested via “stem-like underground with nodes” clues. Therefore, the described underground stem is a rhizome.
92. Which structure is best described as a swollen underground stem with “eyes” that represent buds capable of forming new shoots?
ⓐ. Bulb
ⓑ. Tuber
ⓒ. Corm
ⓓ. Fusiform root
Correct Answer: Tuber
Explanation: A tuber is a modified underground stem that becomes swollen mainly for storage and bears buds known as “eyes.” These eyes are actually nodes with axillary buds, which can sprout into new shoots, making tubers important in vegetative propagation. The presence of eyes is a strong stem-character clue that differentiates tubers from storage roots, which do not bear buds in this pattern. Tubers commonly store carbohydrates, supporting regrowth and survival during adverse periods. Their irregular, thickened form is distinct from the layered bulb or the vertically solid corm. Hence, a swollen underground stem with eyes is best identified as a tuber.
93. A short, vertical, solid underground stem with a tunic-like covering and buds, commonly confused with a bulb, is called a:
ⓐ. Rhizome
ⓑ. Corm
ⓒ. Tuber
ⓓ. Pneumatophore
Correct Answer: Corm
Explanation: A corm is a modified underground stem that is typically short, vertical, and solid (not layered), and it stores food in its swollen stem tissue. It often has a protective outer covering made of dry, scaly leaves, giving a tunic-like appearance. Buds on the corm can produce new shoots, and the structure serves in perennation and vegetative propagation. The solid internal stem tissue distinguishes a corm from a bulb, which consists largely of fleshy leaf bases. Because corms and bulbs can look similar externally, the “solid stem” clue is key. Therefore, the described structure is a corm.
94. A bulb is best identified by the fact that its major food storage tissue is mainly:
ⓐ. Thickened leaf bases arranged in concentric layers
ⓑ. A solid swollen stem with nodes compressed
ⓒ. A horizontal stem with internodes and scaly leaves
ⓓ. A swollen stem with scattered buds called eyes
Correct Answer: Thickened leaf bases arranged in concentric layers
Explanation: A bulb is a specialized underground structure in which the main storage tissue consists of fleshy, swollen leaf bases arranged in layers around a small stem disc. These layers store reserve food and protect the central bud, enabling the plant to survive adverse seasons and regrow. The stem portion in a bulb is usually reduced and forms a basal plate from which adventitious roots can develop. This “layered” organization is the key trait that separates bulbs from corms, which are solid stem swellings, and from tubers, which bear eyes. The concentric leaf-base arrangement is therefore the defining identification point. Hence, bulbs store food mainly in thickened leaf bases in layers.
95. Which set of traits most strongly indicates a rhizome rather than a root-based storage organ?
ⓐ. Presence of root cap and abundant root hairs
ⓑ. Nodes with scale leaves and axillary buds on an underground axis
ⓒ. Absence of buds and presence of a single main root axis
ⓓ. Upward-growing extensions with aeration pores
Correct Answer: Nodes with scale leaves and axillary buds on an underground axis
Explanation: Rhizomes are underground stems, so they retain stem features such as nodes, internodes, scale leaves, and axillary buds. These buds can produce aerial shoots and new rhizome branches, which supports vegetative propagation. Roots, even when modified for storage, do not show nodes and scale leaves in the stem-like pattern, and they do not bear axillary buds along the axis. The presence of a root cap and root hairs would indicate a true root, not a stem modification. The nodal arrangement with buds is therefore the strongest differentiator. Hence, nodes with scale leaves and axillary buds on an underground axis indicate a rhizome.
96. A student cuts an underground structure and sees a solid, starchy interior with a central bud, without concentric leaf layers. The best identification is:
ⓐ. Bulb
ⓑ. Conical root
ⓒ. Rhizome
ⓓ. Corm
Correct Answer: Corm
Explanation: A corm is characterized by a solid internal stem tissue that stores food, often appearing starchy when cut. It bears buds that can give rise to shoots, but unlike bulbs it does not show thick concentric layers of fleshy leaf bases. This internal “solid stem” feature is a core identification trait used to separate corms from bulbs, which have a layered structure. Rhizomes are typically horizontal and show nodes and internodes along a creeping axis, while conical roots are storage tap roots lacking buds. The described solid interior with a central bud aligns closely with a corm. Therefore, the best identification is a corm.
97. The “eyes” of potato are most correctly interpreted as:
ⓐ. Root hairs specialized for mineral absorption
ⓑ. Lenticels meant for gaseous exchange in waterlogged soils
ⓒ. Axillary buds located at nodes on a modified stem
ⓓ. Adventitious roots arising from the stem base
Correct Answer: Axillary buds located at nodes on a modified stem
Explanation: Potato is a stem tuber, and the eyes represent nodes that bear axillary buds. These buds can sprout into new shoots, which is why potato tubers are effective for vegetative propagation. The presence of buds and nodes confirms the stem nature of the tuber, distinguishing it from a storage root which would not show such bud-bearing eyes. While tubers may have small pores for gas exchange, the defining functional feature of eyes is shoot formation capability. This nodal-bud arrangement is a classic identification point in morphology questions. Hence, potato eyes are axillary buds at nodes on a modified stem.
98. Which option correctly matches a common example with the underground stem modification type?
ⓐ. Ginger — rhizome
ⓑ. Onion — tuber
ⓒ. Potato — bulb
ⓓ. Colocasia — rhizome only, never a corm
Correct Answer: Ginger — rhizome
Explanation: Ginger is widely recognized as a rhizome because it is an underground horizontal stem showing nodes, internodes, scale leaves, and buds. These features support both storage and vegetative propagation, which is why ginger pieces with buds can regenerate plants. Onion is classically a bulb, not a tuber, and potato is a tuber, not a bulb. Colocasia is commonly cited as a corm example in basic morphology, so stating it is “never a corm” is not accurate. The most reliable correct pairing among the options is ginger with rhizome. Therefore, ginger — rhizome is the correct match.
99. A key identifying trait that favors “bulb” over “corm” is:
ⓐ. Presence of a root cap at the tip of the structure
ⓑ. Storage mainly in fleshy leaf bases arranged in layers
ⓒ. Presence of upward-growing respiratory roots
ⓓ. Absence of any bud on the structure
Correct Answer: Storage mainly in fleshy leaf bases arranged in layers
Explanation: The most diagnostic difference between a bulb and a corm is the tissue responsible for storage. In bulbs, storage primarily occurs in thickened, fleshy leaf bases arranged in concentric layers around a reduced stem. In corms, storage is mainly in the solid swollen stem tissue, not in layered leaf bases. This layered arrangement in bulbs is visible when cut, making it a practical identification method. Bud presence is not a reliable separator because both bulbs and corms bear buds for regeneration. Therefore, storage in layered fleshy leaf bases strongly favors identification as a bulb.
100. An underground stem modification that mainly enables perennation and rapid regrowth by storing reserves and bearing buds is best represented by:
ⓐ. Rhizome, tuber, bulb, and corm
ⓑ. Fusiform, napiform, and conical roots only
ⓒ. Pneumatophores and haustoria only
ⓓ. Prop roots and stilt roots only
Correct Answer: Rhizome, tuber, bulb, and corm
Explanation: Rhizomes, tubers, bulbs, and corms are all underground stem modifications that store reserve food and bear buds capable of producing new shoots. This combination supports perennation, allowing plants to survive unfavorable seasons and regrow when conditions improve. Their stem nature is reflected in the presence of buds, nodes, or basal plates that enable vegetative propagation. Although they differ in structure—horizontal rhizomes, eye-bearing tubers, layered bulbs, and solid corms—the shared functional theme is storage plus regeneration. Root storage types like conical or fusiform do not represent the full set of underground stem modifications. Hence, rhizome, tuber, bulb, and corm correctly represent underground stem modifications for perennation and regrowth.