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201. In a dicot stem, the presence of cambium between xylem and phloem indicates:
ⓐ. The stem is capable of secondary growth, increasing its diameter
ⓑ. The stem is incapable of secondary growth and will remain herbaceous
ⓒ. The vascular bundles are scattered randomly in the stem
ⓓ. The stem lacks xylem and phloem altogether
Correct Answer: The stem is capable of secondary growth, increasing its diameter
Explanation: The cambium is a meristematic tissue that forms between the xylem and phloem in dicot stems. This cambium layer is essential for secondary growth, where new xylem and phloem are produced, causing the stem to thicken. This process is characteristic of dicot stems and is responsible for the formation of woody tissue. The presence of cambium ensures that the stem can undergo secondary growth and become thicker over time. Therefore, the correct answer is the stem’s capacity for secondary growth.
202. The vascular bundles in a dicot stem with cambium are typically:
ⓐ. Scattered randomly in the ground tissue of the stem
ⓑ. Conjoint with xylem and phloem forming a central core
ⓒ. Present as a single, central bundle surrounded by phloem
ⓓ. Arranged in a circle with cambium present between xylem and phloem
Correct Answer: Arranged in a circle with cambium present between xylem and phloem
Explanation: In dicot stems, the vascular bundles are arranged in a ring, and the cambium layer lies between the xylem and phloem. The cambium is responsible for secondary growth, which increases the diameter of the stem over time. This radial arrangement of vascular bundles with cambium is a key characteristic of dicot stems and allows them to grow in girth. This arrangement contrasts with monocot stems, where vascular bundles are scattered throughout the stem.
203. In a dicot stem with open vascular bundles and cambium present, the open bundles allow for:
ⓐ. A complete absence of secondary growth
ⓑ. The development of a continuous central vascular system with no cambium
ⓒ. The formation of new vascular tissue (secondary xylem and phloem) during secondary growth
ⓓ. The stem to remain thin and herbaceous throughout its life
Correct Answer: The formation of new vascular tissue (secondary xylem and phloem) during secondary growth
Explanation: Open vascular bundles in dicot stems allow for the formation of cambium between the xylem and phloem. The cambium is responsible for secondary growth, producing additional layers of xylem and phloem. This process results in the thickening of the stem over time, contributing to the overall growth and strengthening of the plant. Therefore, the key feature of open vascular bundles with cambium is the ability to form new vascular tissue, facilitating secondary growth.
204. The cambium in dicot stems with open vascular bundles primarily functions to:
ⓐ. Generate new leaves for photosynthesis
ⓑ. Allow for the formation of the central pith
ⓒ. Produce new xylem and phloem during secondary growth
ⓓ. Replace damaged epidermal cells
Correct Answer: Produce new xylem and phloem during secondary growth
Explanation: The cambium in dicot stems is a meristematic tissue found between the xylem and phloem. It is responsible for secondary growth, which leads to the formation of new xylem (wood) and phloem, allowing the stem to increase in girth. This process is essential for woody plants, as it allows them to grow in thickness over time. The cambium does not function in leaf production or epidermal replacement, making option C the most accurate description of its role.
205. In a dicot stem, the presence of cambium and open vascular bundles facilitates:
ⓐ. Decreased rigidity of the stem, limiting growth in height
ⓑ. Increased stem thickness due to secondary xylem and phloem production
ⓒ. The absence of vascular tissue in the stem
ⓓ. Direct transfer of water to the phloem for nutrient transport
Correct Answer: Increased stem thickness due to secondary xylem and phloem production
Explanation: The cambium in dicot stems is a key factor in secondary growth, which involves the production of additional xylem (wood) and phloem. This results in an increase in the stem’s diameter over time, allowing the plant to become more structurally supported. The cambium’s role in producing secondary vascular tissues is critical for the plant’s ability to grow in thickness, making option B the correct answer. Secondary growth is a defining characteristic of dicot stems.
206. The vascular bundles in a dicot stem are described as “open” because:
ⓐ. The xylem and phloem are completely fused, with no space between them
ⓑ. There is a distinct cambium layer present that allows for secondary growth
ⓒ. The vascular bundles are arranged in a scattered manner without any central pattern
ⓓ. The xylem is absent, and only phloem remains for conduction
Correct Answer: There is a distinct cambium layer present that allows for secondary growth
Explanation: “Open” vascular bundles in dicot stems refer to the presence of a cambium layer between the xylem and phloem. This cambium is essential for secondary growth, which increases the stem’s girth by producing additional layers of xylem and phloem. The term “open” is used because the cambium allows for the growth of new vascular tissue, unlike “closed” bundles in monocots, where no cambium is present. Therefore, the presence of cambium is what makes the vascular bundles “open” in dicot stems.
207. Which of the following is NOT a characteristic of dicot stems with open vascular bundles?
ⓐ. Vascular bundles are arranged in a ring around the pith
ⓑ. Cambium is present between xylem and phloem for secondary growth
ⓒ. The vascular bundles are scattered throughout the stem
ⓓ. Secondary growth results in the thickening of the stem
Correct Answer: The vascular bundles are scattered throughout the stem
Explanation: In dicot stems, vascular bundles are arranged in a circle around the central pith. The presence of cambium between the xylem and phloem in these bundles allows for secondary growth, leading to the thickening of the stem. Scattered vascular bundles are a characteristic feature of monocot stems, not dicot stems. Therefore, option C, which describes scattered vascular bundles, is not a characteristic of dicot stems with open vascular bundles.
208. The main difference between dicot and monocot stems in terms of vascular bundles is:
ⓐ. Dicot stems have vascular bundles arranged in a circle, while monocot stems have them scattered
ⓑ. Monocot stems have vascular bundles in a circle, while dicot stems have them scattered
ⓒ. Dicot stems lack vascular bundles altogether
ⓓ. Monocot stems lack cambium in their vascular bundles
Correct Answer: Dicot stems have vascular bundles arranged in a circle, while monocot stems have them scattered
Explanation: The key difference between dicot and monocot stems lies in the arrangement of vascular bundles. In dicot stems, vascular bundles are arranged in a ring around the central pith, and the presence of cambium allows for secondary growth. In contrast, monocot stems have vascular bundles scattered throughout the ground tissue, with no cambium and no secondary growth. This distinction is used to differentiate between dicot and monocot stems in basic plant anatomy.
209. The cambium layer in dicot stems with open vascular bundles is responsible for:
ⓐ. Providing mechanical support to the plant’s roots
ⓑ. Secreting waxes to form a protective cuticle on the epidermis
ⓒ. Generating secondary vascular tissues (xylem and phloem) for growth in girth
ⓓ. Allowing the movement of water from the root to the leaves
Correct Answer: Generating secondary vascular tissues (xylem and phloem) for growth in girth
Explanation: The cambium layer in dicot stems is responsible for secondary growth, which increases the stem’s girth. This occurs because the cambium produces new xylem (wood) towards the center and new phloem towards the outside. This continuous production of vascular tissue is a key feature of dicot stems, allowing them to grow thicker over time. The cambium does not produce waxes or directly facilitate water movement, so option C is the correct answer.
210. The presence of open vascular bundles in dicot stems contributes to:
ⓐ. Reduced stem diameter and lack of secondary growth
ⓑ. Loss of ability to photosynthesize in older plant parts
ⓒ. Limited water and nutrient transport between roots and leaves
ⓓ. Increased stem thickness due to continuous formation of xylem and phloem
Correct Answer: Increased stem thickness due to continuous formation of xylem and phloem
Explanation: Open vascular bundles, where the cambium is present between the xylem and phloem, allow for secondary growth in dicot stems. The cambium produces additional xylem and phloem over time, leading to an increase in stem diameter. This ability for continuous secondary growth is essential for woody dicots and results in the thickening of the stem, which provides structural support for the plant as it grows. This is a major feature distinguishing dicot stems from monocot stems, which do not typically undergo secondary growth.
211. In monocot stems, the vascular bundles are described as:
ⓐ. Arranged in a circle with cambium between xylem and phloem
ⓑ. Scattered randomly throughout the ground tissue
ⓒ. Forming a single large bundle at the center surrounded by ground tissue
ⓓ. Located only in the outermost layer, just beneath the epidermis
Correct Answer: Scattered randomly throughout the ground tissue
Explanation: In monocot stems, vascular bundles are typically scattered throughout the ground tissue, rather than forming a ring as in dicot stems. These bundles contain xylem and phloem and are distributed evenly across the stem. This arrangement is characteristic of monocots and is a key distinction from dicot stems, where vascular bundles are arranged in a ring around a central pith. The scattered arrangement in monocots allows for greater flexibility and is associated with the lack of secondary growth in most monocots.
212. The key characteristic of vascular bundles in monocot stems is that they are:
ⓐ. Conjoint, with phloem and xylem fused in the same bundle
ⓑ. Open, allowing for secondary growth of vascular tissue
ⓒ. Scattered without a defined pattern in the stem
ⓓ. Closed, incapable of forming secondary vascular tissue
Correct Answer: Closed, incapable of forming secondary vascular tissue
Explanation: In monocot stems, the vascular bundles are described as “closed,” meaning they lack cambium between the xylem and phloem, and thus, they do not undergo secondary growth. As a result, monocot stems generally cannot increase in girth by producing new vascular tissue, unlike dicot stems where open vascular bundles allow for secondary growth. This closed arrangement limits the stem’s ability to thicken, a characteristic feature that distinguishes monocots from dicots.
213. Which of the following best describes the arrangement of vascular tissue in monocot stems?
ⓐ. Vascular bundles are arranged in a ring around the central pith
ⓑ. Xylem and phloem are arranged in separate, concentric rings
ⓒ. The vascular tissue forms a single continuous band around the stem
ⓓ. Vascular bundles are scattered throughout the ground tissue without a clear pattern
Correct Answer: Vascular bundles are scattered throughout the ground tissue without a clear pattern
Explanation: In monocot stems, vascular bundles are scattered throughout the ground tissue and do not form a ring like in dicot stems. The scattered arrangement is a defining characteristic of monocot stem anatomy, which differs from the radial arrangement in dicots. This pattern allows for flexibility but limits the capacity for secondary growth since monocots lack a cambium layer between xylem and phloem.
214. A root section shows scattered vascular bundles with no cambium between xylem and phloem. Which of the following is most likely true about the root?
ⓐ. It is a monocot root, which has scattered vascular bundles and lacks secondary growth
ⓑ. It is a dicot root with secondary growth occurring in the vascular bundles
ⓒ. The root is herbaceous, and secondary growth is already underway
ⓓ. It is a stem, as roots do not exhibit scattered vascular bundles
Correct Answer: It is a monocot root, which has scattered vascular bundles and lacks secondary growth
Explanation: Monocot roots, like monocot stems, typically have scattered vascular bundles, which do not possess cambium for secondary growth. The lack of cambium means there is no production of new vascular tissue, and the root cannot thicken over time. This feature is typical of monocots, in contrast to dicots where vascular bundles are arranged in a ring with cambium present for secondary growth.
215. A monocot stem with scattered vascular bundles will likely exhibit:
ⓐ. Secondary growth due to the presence of cambium in the bundles
ⓑ. Primary growth only, as the bundles are not capable of secondary growth
ⓒ. Formation of a central pith with no vascular bundles
ⓓ. Extensive formation of sclerenchyma in the cortex for support
Correct Answer: Primary growth only, as the bundles are not capable of secondary growth
Explanation: In monocot stems, vascular bundles are scattered throughout the ground tissue and lack cambium, meaning they cannot undergo secondary growth. This results in the stem growing in length but not in girth. As a result, monocot stems remain herbaceous and do not form wood or increase in diameter over time. The absence of cambium is a key feature of monocot stems that prevents secondary growth.
216. In a monocot stem, the absence of cambium in the vascular bundles means:
ⓐ. The stem will undergo extensive secondary growth and thickening
ⓑ. The stem will only grow in height but not in diameter
ⓒ. The xylem and phloem will fuse into a single vascular tissue
ⓓ. The phloem will be positioned toward the center of the stem
Correct Answer: The stem will only grow in height but not in diameter
Explanation: The absence of cambium in monocot stems prevents secondary growth, which is the process that increases stem diameter. Without cambium, monocot stems can only grow in height through primary growth, which elongates the stem but does not thicken it. Secondary growth, which contributes to the thickening of stems in dicots, does not occur in monocots because they lack the necessary cambium layer between xylem and phloem.
217. Which of the following structures is typically absent in monocot stems, making it impossible for them to undergo secondary growth?
ⓐ. Xylem
ⓑ. Phloem
ⓒ. Pith
ⓓ. Cambium
Correct Answer: Cambium
Explanation: The absence of cambium is a defining characteristic of monocot stems. Cambium is a meristematic tissue located between the xylem and phloem that enables secondary growth, allowing the stem to thicken over time. Since monocots lack cambium, they are incapable of undergoing secondary growth. As a result, monocot stems generally grow in height but do not increase in diameter. The absence of cambium is the key factor that prevents monocots from forming woody tissue.
218. Which feature best distinguishes monocot stems with scattered vascular bundles from dicot stems?
ⓐ. The presence of secondary growth and the cambium layer in monocots
ⓑ. The absence of vascular bundles in the cortex of monocot stems
ⓒ. The radial arrangement of vascular bundles in dicot stems and scattered bundles in monocots
ⓓ. The presence of a large central pith in monocot stems
Correct Answer: The radial arrangement of vascular bundles in dicot stems and scattered bundles in monocots
Explanation: The most distinguishing feature between monocot and dicot stems is the arrangement of vascular bundles. In dicot stems, vascular bundles are typically arranged in a circle or ring around the central pith, while in monocot stems, vascular bundles are scattered throughout the stem. This arrangement in monocots prevents secondary growth, as the lack of cambium means that the stem cannot thicken over time. The presence of a central pith is not a key differentiator between the two, as both types of stems can have a pith, but its prominence varies.
219. Which of the following is true for monocot stems with scattered vascular bundles?
ⓐ. They can perform secondary growth like dicot stems
ⓑ. They can grow in diameter due to the activity of the cambium
ⓒ. They show primary growth only and remain herbaceous
ⓓ. They lack vascular tissue entirely in the stem
Correct Answer: They show primary growth only and remain herbaceous
Explanation: Monocot stems have scattered vascular bundles and lack cambium, meaning they cannot undergo secondary growth. Therefore, monocot stems only grow in length through primary growth and do not thicken over time. This is in contrast to dicot stems, which have vascular bundles arranged in a ring and possess cambium for secondary growth, allowing them to become woody. Monocot stems typically remain herbaceous and do not form woody tissue.
220. Which of the following statements about monocot stems is true regarding the vascular bundles?
ⓐ. The vascular bundles are arranged in a circle, allowing for secondary growth
ⓑ. The vascular bundles are absent, and the stem is incapable of water transport
ⓒ. The vascular bundles are arranged in a single central bundle for water transport
ⓓ. The vascular bundles are scattered, and the stem does not undergo secondary growth
Correct Answer: The vascular bundles are scattered, and the stem does not undergo secondary growth
Explanation: In monocot stems, vascular bundles are scattered throughout the stem’s ground tissue. These bundles lack cambium, meaning monocot stems cannot undergo secondary growth to increase their diameter. The scattered vascular bundle arrangement allows for the efficient transport of water and nutrients but limits the plant’s ability to thicken over time. Unlike dicot stems, which undergo secondary growth, monocot stems remain herbaceous and grow primarily in length, not in girth.
221. In monocot stems, the vascular bundles are described as:
ⓐ. Scattered throughout the ground tissue, lacking cambium
ⓑ. Arranged in a ring around the central pith
ⓒ. Open, with cambium between xylem and phloem
ⓓ. Located at the center of the stem with phloem inside
Correct Answer: Scattered throughout the ground tissue, lacking cambium
Explanation: In monocot stems, vascular bundles are scattered throughout the ground tissue. These bundles are closed, meaning they lack cambium, which prevents secondary growth. Without cambium, monocot stems cannot increase in diameter and remain herbaceous, growing only in height. This is a key characteristic of monocot stems compared to dicot stems, where vascular bundles are arranged in a ring.
222. The absence of cambium in monocot stems results in:
ⓐ. Secondary growth leading to an increase in stem diameter
ⓑ. A continuous increase in stem height
ⓒ. The inability to increase the stem’s diameter, remaining herbaceous
ⓓ. The formation of secondary phloem and xylem
Correct Answer: The inability to increase the stem’s diameter, remaining herbaceous
Explanation: The absence of cambium in monocot stems prevents secondary growth, which is responsible for thickening the stem. Without cambium, monocot stems cannot form new vascular tissue, and as a result, they remain herbaceous, growing only in height. Secondary growth, which is common in dicots, does not occur in monocots.
223. The closed vascular bundles in monocot stems are:
ⓐ. Arranged in a continuous ring around the pith
ⓑ. Scattered throughout the stem without any central arrangement
ⓒ. Open, allowing for secondary growth and thickening
ⓓ. Located at the center of the stem with phloem inside
Correct Answer: Scattered throughout the stem without any central arrangement
Explanation: In monocot stems, vascular bundles are scattered throughout the stem. These bundles lack cambium, which prevents secondary growth. This scattered arrangement allows flexibility but limits the stem’s ability to thicken. This is a major difference from dicot stems, where vascular bundles are typically arranged in a ring.
224. In monocot stems, the lack of cambium results in:
ⓐ. The ability for the stem to thicken through secondary growth
ⓑ. The formation of new vascular tissue for transport
ⓒ. The stem remaining herbaceous and growing only in height
ⓓ. The development of woody tissue in the stem
Correct Answer: The stem remaining herbaceous and growing only in height
Explanation: The lack of cambium in monocot stems means that they cannot undergo secondary growth. Secondary growth allows stems to thicken by producing additional xylem and phloem. Without cambium, monocot stems remain herbaceous and grow only in height. This is a key difference between monocots and dicots, where dicots can form wood through secondary growth.
225. Monocot stems are typically herbaceous because:
ⓐ. They have vascular bundles arranged in a ring for secondary growth
ⓑ. They lack cambium and cannot form secondary xylem or phloem
ⓒ. They form wood-like tissues in older parts of the stem
ⓓ. They have a continuous central vascular system
Correct Answer: They lack cambium and cannot form secondary xylem or phloem
Explanation: The lack of cambium in monocot stems means that they cannot undergo secondary growth, which is responsible for forming new vascular tissues and increasing stem thickness. As a result, monocot stems remain herbaceous and grow only in height. In contrast, dicot stems can form secondary vascular tissues through cambium, resulting in wood formation.
226. The vascular bundles in monocot stems contribute to:
ⓐ. The formation of a woody central vascular cylinder
ⓑ. The transport of water and nutrients through the xylem and phloem
ⓒ. The stem’s ability to grow in diameter and form wood
ⓓ. The production of aerenchyma for gas exchange
Correct Answer: The transport of water and nutrients through the xylem and phloem
Explanation: Despite the lack of cambium, monocot stems still rely on vascular bundles to perform essential functions, such as transporting water, minerals, and nutrients. The xylem moves water and minerals, while the phloem transports sugars and other nutrients. These vascular bundles are key to monocot plant function, even though secondary growth does not occur.
227. Monocot stems lack the ability to thicken because:
ⓐ. The vascular bundles are arranged in a central cylinder
ⓑ. The xylem and phloem are fused together, blocking secondary growth
ⓒ. There is no cambium between the xylem and phloem
ⓓ. The stem has a central pith that absorbs nutrients
Correct Answer: There is no cambium between the xylem and phloem
Explanation: The absence of cambium in monocot stems prevents the formation of new xylem and phloem. Cambium is necessary for secondary growth, which increases the stem’s diameter. Without cambium, monocot stems cannot thicken and remain herbaceous, unlike dicot stems, which undergo secondary growth and form woody tissue.
228. Which of the following is true for monocot stems with closed vascular bundles?
ⓐ. They undergo secondary growth, increasing stem thickness
ⓑ. They have vascular bundles arranged in a ring around the pith
ⓒ. They remain herbaceous and do not form woody tissue
ⓓ. They possess a central vascular cylinder that allows for thickening
Correct Answer: They remain herbaceous and do not form woody tissue
Explanation: Monocot stems with closed vascular bundles cannot undergo secondary growth because they lack cambium. This means they do not form woody tissue and remain herbaceous. Unlike dicot stems, which have cambium and undergo secondary growth, monocot stems grow only in height and do not thicken.
229. The lack of secondary growth in monocot stems is due to:
ⓐ. The presence of cambium, which produces new vascular tissue
ⓑ. The closed vascular bundles, which lack cambium
ⓒ. The scattered arrangement of vascular bundles throughout the stem
ⓓ. The formation of aerenchyma for gas exchange
Correct Answer: The closed vascular bundles, which lack cambium
Explanation: The closed vascular bundles in monocot stems lack cambium, which is required for secondary growth. Cambium produces new vascular tissue, allowing the stem to thicken. Without cambium, monocot stems cannot form new vascular tissue and remain herbaceous, growing only in height. Secondary growth, which occurs in dicot stems, is absent in monocots.
230. In monocot stems, the vascular bundles are typically:
ⓐ. Scattered throughout the stem, without a clear pattern
ⓑ. Arranged in a ring around the central pith
ⓒ. Concentric, with xylem and phloem alternating in separate layers
ⓓ. Found in a continuous vascular cylinder around the stem
Correct Answer: Scattered throughout the stem, without a clear pattern
Explanation: In monocot stems, vascular bundles are scattered throughout the ground tissue. This scattered arrangement is characteristic of monocot stems, allowing flexibility but preventing secondary growth. Unlike dicot stems, where vascular bundles are arranged in a ring, monocots do not undergo secondary growth and remain herbaceous, growing only in height.
231. In dorsiventral leaves, the palisade mesophyll is responsible for:
ⓐ. Transporting water and nutrients to the leaf cells
ⓑ. Providing structural support to the leaf
ⓒ. Performing the majority of photosynthesis due to its tightly packed cells
ⓓ. Storing water and sugars for the plant
Correct Answer: Performing the majority of photosynthesis due to its tightly packed cells
Explanation: The palisade mesophyll is located just beneath the upper epidermis of dorsiventral leaves and is the primary site for photosynthesis. This layer consists of column-shaped cells that are tightly packed with chloroplasts. The high concentration of chloroplasts allows for maximum light absorption and efficient conversion of light energy into chemical energy, which is essential for the plant’s growth and development. The close packing of these cells ensures that the leaf can absorb as much light as possible for photosynthesis.
232. The spongy mesophyll in dorsiventral leaves plays an important role in:
ⓐ. Providing structural rigidity to the leaf
ⓑ. Facilitating the movement of gases (oxygen, carbon dioxide) for photosynthesis
ⓒ. Maximizing light absorption for photosynthesis
ⓓ. Protecting the leaf from excessive water loss
Correct Answer: Facilitating the movement of gases (oxygen, carbon dioxide) for photosynthesis
Explanation: The spongy mesophyll is composed of loosely arranged cells with large intercellular spaces that allow gases such as carbon dioxide and oxygen to diffuse easily within the leaf. This facilitates the gas exchange necessary for photosynthesis, as carbon dioxide enters the leaf and oxygen exits during the process. These cells also contribute to the movement of water vapor during transpiration. The structure of the spongy mesophyll ensures efficient gas exchange and supports the overall process of photosynthesis.
233. The majority of stomata in a dorsiventral leaf are found:
ⓐ. On the upper surface of the leaf
ⓑ. On the lower surface of the leaf
ⓒ. Equally distributed on both the upper and lower surfaces
ⓓ. Only on the epidermis surrounding the vascular bundles
Correct Answer: On the lower surface of the leaf
Explanation: In dorsiventral leaves, most of the stomata are located on the lower surface. This positioning helps minimize water loss through transpiration, as the lower surface is less exposed to direct sunlight and wind. The stomata open and close to regulate the exchange of gases, allowing carbon dioxide to enter for photosynthesis and oxygen to exit as a byproduct. By positioning stomata on the underside of the leaf, the plant reduces water loss while still allowing for gas exchange.
234. The primary function of the palisade mesophyll in dorsiventral leaves is:
ⓐ. Storing nutrients and sugars
ⓑ. Protecting the leaf from pathogens
ⓒ. Providing a barrier to water loss
ⓓ. Performing photosynthesis
Correct Answer: Performing photosynthesis
Explanation: The palisade mesophyll is the primary site for photosynthesis in dorsiventral leaves. These cells contain numerous chloroplasts, which capture light energy and use it to convert carbon dioxide and water into glucose, an essential source of energy for the plant. The palisade mesophyll is positioned just beneath the upper epidermis, allowing it to absorb sunlight efficiently. This dense layer of cells ensures that the plant can produce enough energy for growth and reproduction through photosynthesis.
235. The stomata in leaves are responsible for:
ⓐ. Absorbing sunlight for photosynthesis
ⓑ. Allowing the exchange of gases, such as oxygen and carbon dioxide
ⓒ. Storing water and nutrients
ⓓ. Protecting the leaf from pathogens
Correct Answer: Allowing the exchange of gases, such as oxygen and carbon dioxide
Explanation: Stomata are small pores on the surface of leaves, primarily on the lower epidermis, that regulate gas exchange between the plant and the environment. They allow carbon dioxide to enter the leaf for photosynthesis and oxygen to exit as a byproduct. Additionally, stomata facilitate transpiration, which is the process of water vapor exiting the plant. The opening and closing of stomata are controlled by guard cells, which respond to environmental conditions to balance gas exchange and water conservation.
236. The palisade mesophyll is typically located:
ⓐ. Beneath the upper epidermis, near the leaf surface
ⓑ. Beneath the lower epidermis
ⓒ. In the center of the leaf
ⓓ. In the vascular bundle
Correct Answer: Beneath the upper epidermis, near the leaf surface
Explanation: The palisade mesophyll is located just beneath the upper epidermis of dorsiventral leaves. This position allows it to receive the most direct sunlight, making it the ideal site for photosynthesis. The tightly packed columnar cells of the palisade mesophyll contain numerous chloroplasts, which absorb light and convert it into chemical energy through photosynthesis. This layer is the most important for the plant’s energy production and is crucial for overall plant health and growth.
237. The primary function of the spongy mesophyll in dorsiventral leaves is:
ⓐ. Absorbing sunlight for photosynthesis
ⓑ. Protecting the leaf from water loss
ⓒ. Providing structural support to the leaf
ⓓ. Facilitating gas exchange and storing nutrients
Correct Answer: Facilitating gas exchange and storing nutrients
Explanation: The spongy mesophyll is located beneath the palisade mesophyll and consists of loosely arranged cells with large intercellular spaces. These spaces allow for efficient gas exchange, enabling carbon dioxide to enter the leaf for photosynthesis and oxygen to exit as a byproduct. The spongy mesophyll also serves as a storage area for water and other nutrients. While the palisade mesophyll is the main site for photosynthesis, the spongy mesophyll supports this process by allowing gases to diffuse and participate in the plant’s overall metabolic activities.
238. Stomatal regulation is important in dorsiventral leaves to:
ⓐ. Maximize photosynthesis by opening stomata continuously
ⓑ. Minimize water loss while allowing gas exchange
ⓒ. Protect the plant from herbivores
ⓓ. Provide nutrients to the leaf through stomatal pores
Correct Answer: Minimize water loss while allowing gas exchange
Explanation: Stomatal regulation is crucial for maintaining water balance in plants. Stomata open to allow carbon dioxide to enter for photosynthesis and oxygen to exit as a byproduct. However, when stomata are open, water vapor can also escape through transpiration. Therefore, stomatal regulation helps balance the need for gas exchange with the need to conserve water. In dry or hot conditions, stomata may close to reduce water loss, while still allowing the plant to obtain the necessary gases for photosynthesis.
239. The major difference between the palisade and spongy mesophyll is:
ⓐ. Palisade mesophyll is responsible for gas exchange, while spongy mesophyll performs photosynthesis
ⓑ. Spongy mesophyll cells are more densely packed than palisade mesophyll cells
ⓒ. Palisade mesophyll contains more chloroplasts and is primarily responsible for photosynthesis
ⓓ. Spongy mesophyll is located near the epidermis, while palisade mesophyll is deep inside the leaf
Correct Answer: Palisade mesophyll contains more chloroplasts and is primarily responsible for photosynthesis
Explanation: The palisade mesophyll is composed of tightly packed column-shaped cells that contain a high concentration of chloroplasts. This enables it to be the primary site for photosynthesis in dorsiventral leaves. In contrast, the spongy mesophyll consists of loosely arranged cells with large intercellular spaces, facilitating gas exchange and the movement of water vapor. While both mesophyll types contribute to photosynthesis, the palisade mesophyll plays the dominant role due to its higher chloroplast content and closer proximity to light.
240. The stomata in dorsiventral leaves are typically located:
ⓐ. On the lower surface of the leaf
ⓑ. On the upper surface of the leaf
ⓒ. Equally distributed on both the upper and lower surfaces
ⓓ. Only on the epidermis surrounding the vascular bundles
Correct Answer: On the lower surface of the leaf
Explanation: In dorsiventral leaves, most of the stomata are located on the lower surface. This helps reduce water loss through transpiration, as the lower surface is typically less exposed to direct sunlight and wind. The stomata allow for gas exchange, permitting carbon dioxide to enter the leaf for photosynthesis and oxygen to exit as a byproduct. By positioning stomata on the underside, the plant conserves water while still ensuring that necessary gases can diffuse into and out of the leaf.
241. The palisade mesophyll is primarily responsible for:
ⓐ. Storing water and sugars
ⓑ. Performing the majority of photosynthesis in the leaf
ⓒ. Facilitating the exchange of gases for respiration
ⓓ. Providing mechanical support to the leaf
Correct Answer: Performing the majority of photosynthesis in the leaf
Explanation: The palisade mesophyll is the main site for photosynthesis in dorsiventral leaves. It consists of tightly packed, elongated cells that contain numerous chloroplasts. These chloroplasts capture light energy, allowing the plant to convert carbon dioxide and water into glucose and oxygen. The palisade mesophyll is located just beneath the upper epidermis to maximize sunlight exposure, making it the most efficient layer for photosynthesis in the leaf.
242. The spongy mesophyll in dorsiventral leaves is characterized by:
ⓐ. Tightly packed cells that absorb sunlight for photosynthesis
ⓑ. Cells filled with water that support the plant structure
ⓒ. A high concentration of chloroplasts for efficient photosynthesis
ⓓ. Loosely arranged cells with large intercellular spaces for gas exchange
Correct Answer: Loosely arranged cells with large intercellular spaces for gas exchange
Explanation: The spongy mesophyll consists of loosely packed cells with large intercellular spaces that facilitate the movement of gases such as carbon dioxide and oxygen. These spaces allow for efficient gas exchange necessary for photosynthesis and respiration. While the palisade mesophyll is responsible for absorbing sunlight, the spongy mesophyll plays a key role in ensuring the plant has access to the gases required for these processes.
243. Most of the stomata in dorsiventral leaves are located on:
ⓐ. The upper surface of the leaf, exposed to sunlight
ⓑ. The lower surface of the leaf, protected from direct sunlight
ⓒ. Both the upper and lower surfaces, in equal numbers
ⓓ. The edges of the leaf for maximum gas exchange
Correct Answer: The lower surface of the leaf, protected from direct sunlight
Explanation: In dorsiventral leaves, most of the stomata are located on the lower surface of the leaf. This positioning helps minimize water loss through transpiration since the lower surface is less exposed to direct sunlight and wind. Stomata allow the exchange of gases such as carbon dioxide, which enters for photosynthesis, and oxygen, which exits as a byproduct. This arrangement helps the plant balance the need for gas exchange with water conservation.
244. In dorsiventral leaves, the presence of the palisade mesophyll contributes primarily to:
ⓐ. The storage of sugars and water
ⓑ. Gas exchange between the leaf and atmosphere
ⓒ. The majority of light absorption for photosynthesis
ⓓ. The production of hormones and growth factors
Correct Answer: The majority of light absorption for photosynthesis
Explanation: The palisade mesophyll is the primary site for photosynthesis in dorsiventral leaves. It consists of tightly packed, elongated cells that contain many chloroplasts, which are responsible for absorbing light energy. This enables the plant to convert light into chemical energy through photosynthesis, where carbon dioxide and water are transformed into glucose and oxygen. This efficient light absorption is essential for the plant’s energy production.
245. The primary function of stomata in dorsiventral leaves is to:
ⓐ. Absorb light for photosynthesis
ⓑ. Protect the leaf from pathogens
ⓒ. Store nutrients for the plant
ⓓ. Regulate water loss and gas exchange
Correct Answer: Regulate water loss and gas exchange
Explanation: The stomata in dorsiventral leaves regulate the exchange of gases such as carbon dioxide and oxygen, which are crucial for photosynthesis and respiration. Stomata also play an essential role in transpiration, the process by which water vapor exits the leaf. By opening and closing, stomata control water loss and help maintain the plant’s water balance. This regulation ensures that the plant can perform photosynthesis while minimizing unnecessary water loss.
246. The spongy mesophyll in dorsiventral leaves mainly aids in:
ⓐ. Structural support for the leaf
ⓑ. Maximizing photosynthesis by absorbing sunlight
ⓒ. Facilitating the diffusion of gases necessary for photosynthesis
ⓓ. Storing nutrients and sugars for future use
Correct Answer: Facilitating the diffusion of gases necessary for photosynthesis
Explanation: The spongy mesophyll consists of loosely arranged cells with large intercellular spaces, which facilitates the diffusion of gases like carbon dioxide and oxygen. This gas exchange is essential for photosynthesis, as carbon dioxide enters the leaf to be used in the production of glucose, and oxygen exits as a byproduct. The spongy mesophyll is crucial for ensuring that the gases needed for photosynthesis can move efficiently within the leaf.
247. The palisade mesophyll in dorsiventral leaves is usually located:
ⓐ. Below the lower epidermis to protect it from water loss
ⓑ. Beneath the upper epidermis, where it can receive maximum sunlight
ⓒ. In the central part of the leaf, surrounded by spongy mesophyll
ⓓ. Above the vascular bundles for easier nutrient transport
Correct Answer: Beneath the upper epidermis, where it can receive maximum sunlight
Explanation: The palisade mesophyll is located just beneath the upper epidermis of dorsiventral leaves. This placement allows the cells in this layer to receive the maximum amount of sunlight, which is crucial for photosynthesis. The tightly packed cells of the palisade mesophyll contain many chloroplasts, which absorb light energy to convert carbon dioxide and water into glucose and oxygen. This positioning ensures the plant’s photosynthetic efficiency.
248. Stomatal pores in dorsiventral leaves are typically:
ⓐ. Present in high density on the lower surface, allowing gas exchange
ⓑ. Distributed uniformly on the upper surface for maximum exposure
ⓒ. Absent in plants adapted to dry climates
ⓓ. Only present around the vascular bundles for nutrient exchange
Correct Answer: Present in high density on the lower surface, allowing gas exchange
Explanation: Stomatal pores are most commonly found in high density on the lower surface of dorsiventral leaves. This location minimizes water loss through transpiration while still allowing the plant to exchange gases like carbon dioxide and oxygen. The lower surface is less exposed to direct sunlight, which reduces evaporation, helping the plant conserve water while still facilitating the necessary gas exchange for photosynthesis and respiration.
249. In a dorsiventral leaf, the function of the spongy mesophyll is primarily to:
ⓐ. Absorb sunlight for photosynthesis
ⓑ. Store water for future use
ⓒ. Facilitate the exchange of gases such as oxygen and carbon dioxide
ⓓ. Provide mechanical support to the leaf
Correct Answer: Facilitate the exchange of gases such as oxygen and carbon dioxide
Explanation: The spongy mesophyll consists of loosely arranged cells with large intercellular spaces. These spaces allow for the efficient movement of gases, such as carbon dioxide, which enters the leaf for photosynthesis, and oxygen, which exits as a byproduct. The spongy mesophyll is key in facilitating the gas exchange required for the plant’s metabolic activities. Additionally, it plays a role in the movement of water vapor during transpiration.
250. The majority of stomata in dorsiventral leaves are located on:
ⓐ. The upper surface of the leaf, exposed to sunlight
ⓑ. The lower surface of the leaf, protected from direct sunlight
ⓒ. Equally distributed on both the upper and lower surfaces
ⓓ. The edges of the leaf for maximum gas exchange
Correct Answer: The lower surface of the leaf, protected from direct sunlight
Explanation: In dorsiventral leaves, most of the stomata are located on the lower surface, which is shielded from direct sunlight. This positioning helps minimize water loss due to evaporation, as the lower surface is cooler and less exposed to wind and sunlight. Stomata on the lower surface allow carbon dioxide to enter for photosynthesis while releasing oxygen. The regulation of water loss through transpiration is also more efficient when stomata are located on the underside of the leaf.
251. In isobilateral leaves, the structure of the mesophyll is characterized by:
ⓐ. A highly developed palisade mesophyll on both sides
ⓑ. An equal distribution of palisade and spongy mesophyll on both sides
ⓒ. A single layer of palisade cells on the upper surface
ⓓ. A prominent spongy mesophyll with larger intercellular spaces
Correct Answer: An equal distribution of palisade and spongy mesophyll on both sides
Explanation: In isobilateral leaves, both the upper and lower surfaces of the leaf contain similar mesophyll structures. Both surfaces have an equal distribution of palisade and spongy mesophyll, with palisade cells arranged on both sides of the leaf. This arrangement allows for effective photosynthesis on both sides of the leaf, maximizing light absorption and gas exchange. The structure is adapted to environments where leaves need to perform photosynthesis efficiently on both surfaces.
252. The bulliform cells in isobilateral leaves primarily function in:
ⓐ. Photosynthesis by trapping sunlight
ⓑ. Facilitating the movement of water through the leaf
ⓒ. The regulation of leaf rolling in response to water loss
ⓓ. Providing structural support for the leaf
Correct Answer: The regulation of leaf rolling in response to water loss
Explanation: Bulliform cells in isobilateral leaves are large, specialized cells that are located along the central vein of the leaf. These cells play a key role in regulating leaf rolling or folding, especially under conditions of water stress. When the plant experiences dehydration, bulliform cells lose turgidity, causing the leaf to curl or roll up. This reduces the surface area exposed to the atmosphere and minimizes water loss, helping the plant conserve moisture during periods of drought or excessive heat.
253. In isobilateral leaves, the presence of palisade mesophyll on both sides of the leaf is beneficial for:
ⓐ. Increasing the efficiency of photosynthesis on both surfaces
ⓑ. Reducing the need for gas exchange
ⓒ. Preventing water loss through transpiration
ⓓ. Providing protection against herbivory
Correct Answer: Increasing the efficiency of photosynthesis on both surfaces
Explanation: The presence of palisade mesophyll on both the upper and lower surfaces of isobilateral leaves increases the leaf’s ability to capture sunlight for photosynthesis. By having palisade cells on both sides, the leaf can perform photosynthesis more effectively, even when the leaf is positioned in a way that minimizes light absorption from one direction. This is particularly useful for plants in environments where light exposure is diffuse or when the leaf is exposed to sunlight from multiple angles.
254. In isobilateral leaves, bulliform cells are most commonly found:
ⓐ. Near the edges of the leaf for water storage
ⓑ. In the vascular bundles to store sugars
ⓒ. Along the midrib and veins of the leaf for leaf movement regulation
ⓓ. Between the epidermal layers to protect the leaf
Correct Answer: Along the midrib and veins of the leaf for leaf movement regulation
Explanation: Bulliform cells are specialized cells located along the midrib and veins of isobilateral leaves. These cells help control leaf rolling or folding in response to water stress. When the plant is dehydrated, the bulliform cells lose turgidity, causing the leaf to roll or fold, which reduces the leaf’s surface area and minimizes water loss through transpiration. This response is a vital adaptation for maintaining water conservation during periods of drought or high environmental stress.
255. The primary function of bulliform cells in isobilateral leaves is to:
ⓐ. Absorb water from the soil and transport it to the leaf
ⓑ. Facilitate the movement of gases through the leaf
ⓒ. Regulate leaf size by controlling cell expansion
ⓓ. Prevent excessive water loss by causing leaf rolling during drought
Correct Answer: Prevent excessive water loss by causing leaf rolling during drought
Explanation: Bulliform cells play a critical role in reducing water loss from isobilateral leaves during times of water scarcity. When the plant experiences water stress, the bulliform cells lose turgor pressure, causing the leaf to roll or fold. This reduces the surface area exposed to the atmosphere, thus minimizing transpiration. This mechanism helps the plant conserve water and survive periods of drought or high temperatures. Bulliform cells are a key adaptation for plants growing in arid or semi-arid environments.
256. In isobilateral leaves, the symmetry of the leaf results in:
ⓐ. A significant difference in mesophyll structure on the upper and lower sides
ⓑ. Efficient photosynthesis due to similar mesophyll distribution on both sides
ⓒ. A large central vascular bundle for water transport
ⓓ. An increase in leaf thickness for structural support
Correct Answer: Efficient photosynthesis due to similar mesophyll distribution on both sides
Explanation: The isobilateral leaf structure is symmetrical, with palisade mesophyll on both the upper and lower surfaces of the leaf. This symmetry allows for efficient photosynthesis on both sides of the leaf, as both surfaces are capable of absorbing light and performing photosynthesis. The equal distribution of palisade cells on both surfaces maximizes the plant’s ability to capture light and produce food, particularly in environments where light is diffuse or available from multiple directions.
257. In isobilateral leaves, the arrangement of stomata is typically:
ⓐ. More concentrated on the upper surface to maximize gas exchange
ⓑ. Absent, as gas exchange occurs through lenticels
ⓒ. More concentrated on the lower surface to minimize water loss
ⓓ. Distributed equally on both the upper and lower surfaces
Correct Answer: More concentrated on the lower surface to minimize water loss
Explanation: In isobilateral leaves, most stomata are concentrated on the lower surface of the leaf. This arrangement helps to reduce water loss through transpiration because the lower surface is less exposed to direct sunlight and wind, which are factors that increase evaporation. By positioning stomata on the lower surface, the plant minimizes water loss while still allowing for gas exchange, which is crucial for photosynthesis and respiration.
258. The presence of bulliform cells in isobilateral leaves helps the plant to:
ⓐ. Absorb more light for photosynthesis
ⓑ. Transport water more efficiently within the leaf
ⓒ. Regulate leaf size for better exposure to sunlight
ⓓ. Minimize water loss during drought conditions
Correct Answer: Minimize water loss during drought conditions
Explanation: Bulliform cells in isobilateral leaves are large, specialized cells found along the midrib and veins of the leaf. These cells are responsible for regulating leaf movement in response to water loss. When the plant is under water stress, bulliform cells lose turgidity, causing the leaf to curl or fold. This reduces the surface area exposed to the atmosphere, minimizing water loss through transpiration. This mechanism is essential for water conservation during periods of drought.
259. The function of the stomata in isobilateral leaves is to:
ⓐ. Absorb sunlight for photosynthesis
ⓑ. Facilitate the movement of water through the leaf
ⓒ. Allow the exchange of gases (oxygen, carbon dioxide) and control water loss
ⓓ. Store nutrients and sugars for later use
Correct Answer: Allow the exchange of gases (oxygen, carbon dioxide) and control water loss
Explanation: Stomata are small pores on the surface of leaves that regulate gas exchange and water loss. In isobilateral leaves, stomata are primarily located on the lower surface to minimize water loss while still allowing for the necessary exchange of gases like carbon dioxide for photosynthesis and oxygen as a byproduct. The opening and closing of stomata are controlled by guard cells, which respond to environmental conditions such as humidity, light, and water availability.
260. In isobilateral leaves, the structure of the mesophyll ensures that:
ⓐ. The leaf can perform photosynthesis on both sides efficiently
ⓑ. The leaf remains flexible and lightweight for better light absorption
ⓒ. The leaf has a thick epidermis for structural support
ⓓ. The leaf can store large amounts of water for future use
Correct Answer: The leaf can perform photosynthesis on both sides efficiently
Explanation: In isobilateral leaves, the palisade and spongy mesophyll are equally distributed on both the upper and lower surfaces of the leaf. This symmetry allows both surfaces to capture sunlight and perform photosynthesis efficiently. The equal distribution of photosynthetic cells on both sides of the leaf maximizes light absorption and gas exchange, making it an effective adaptation for plants exposed to light from multiple angles or environments with diffuse light.
261. The vascular cambium is responsible for:
ⓐ. Increasing the length of the stem
ⓑ. Transport of water and nutrients through the stem
ⓒ. Formation of the epidermis
ⓓ. Producing secondary xylem and phloem
Correct Answer: Producing secondary xylem and phloem
Explanation: The vascular cambium is a meristematic tissue found between the xylem and phloem in the vascular bundles. It is responsible for secondary growth, where it produces secondary xylem (wood) on the inside and secondary phloem on the outside. This growth contributes to the thickening of the stem, which allows plants to increase in diameter over time. The vascular cambium plays a key role in the development of woody tissues and overall stem support.
262. The cambial ring is formed by:
ⓐ. A layer of cambium that surrounds the vascular bundles
ⓑ. The fusion of primary xylem and phloem
ⓒ. The development of cork cells in the outer bark
ⓓ. The differentiation of ground tissue into vascular tissue
Correct Answer: A layer of cambium that surrounds the vascular bundles
Explanation: The cambial ring is formed when the vascular cambium develops as a continuous layer that surrounds the vascular bundles. This ring is essential for secondary growth, as it divides to produce new layers of xylem and phloem. The cambial ring plays a critical role in the thickening of stems, which is characteristic of woody plants. This growth allows plants to increase in girth and support larger structures over time.
263. The formation of secondary xylem and phloem in the vascular cambium is primarily due to:
ⓐ. Meristematic activity in the cortex
ⓑ. Differentiation of ground tissue into vascular tissue
ⓒ. The splitting of the cambial cells into two daughter cells
ⓓ. The expansion of existing xylem and phloem cells
Correct Answer: The splitting of the cambial cells into two daughter cells
Explanation: The vascular cambium produces secondary xylem and phloem through its meristematic activity. The cambial cells divide periclinally (parallel to the surface), producing two daughter cells: one that remains meristematic and continues to divide, and another that differentiates into secondary vascular tissue. This process leads to the formation of secondary xylem on the inside and secondary phloem on the outside, contributing to the thickening of the plant’s stem.
264. The secondary phloem produced by the vascular cambium is responsible for:
ⓐ. Transporting water and minerals
ⓑ. Transporting sugars and organic nutrients
ⓒ. Providing structural support to the plant
ⓓ. Storing excess sugars for future use
Correct Answer: Transporting sugars and organic nutrients
Explanation: Secondary phloem, produced by the vascular cambium, is responsible for the transport of sugars and organic nutrients throughout the plant. This tissue is located on the outside of the cambium ring and helps distribute the products of photosynthesis from the leaves to other parts of the plant, including roots and stems. As the plant grows, the production of secondary phloem increases, allowing the plant to transport nutrients effectively.
265. The process of secondary growth is initiated by:
ⓐ. The formation of the vascular cambium
ⓑ. The growth of the primary meristems
ⓒ. The development of the apical meristem
ⓓ. The differentiation of the ground tissue
Correct Answer: The formation of the vascular cambium
Explanation: Secondary growth begins with the formation of the vascular cambium, which develops between the primary xylem and phloem. The cambium is a meristematic tissue, capable of continuous division, producing new cells that differentiate into secondary xylem and phloem. This growth results in the thickening of the plant’s stems and roots. The vascular cambium plays a crucial role in the formation of woody tissue, which allows the plant to grow in diameter over time.
266. The vascular cambium is located:
ⓐ. Between the epidermis and cortex
ⓑ. In the pericycle of roots
ⓒ. In the center of the stem surrounded by vascular tissue
ⓓ. Between the primary xylem and primary phloem
Correct Answer: Between the primary xylem and primary phloem
Explanation: The vascular cambium is located between the primary xylem and primary phloem in the vascular bundles. It is a meristematic tissue responsible for secondary growth. As it divides, it produces secondary xylem (wood) to the inside and secondary phloem to the outside. This process contributes to the thickening of the plant’s stem and roots, allowing it to support more vascular tissue as it grows.
267. The formation of secondary xylem and phloem is an example of:
ⓐ. Primary growth, which increases the length of the plant
ⓑ. Secondary growth, which increases the diameter of the plant
ⓒ. Meristematic growth, which occurs at the shoot tips
ⓓ. Apical growth, which happens at the root tips
Correct Answer: Secondary growth, which increases the diameter of the plant
Explanation: Secondary growth is the process that increases the diameter or girth of a plant. It occurs through the activity of the vascular cambium, which produces secondary xylem (wood) and secondary phloem. This growth allows plants to become larger and stronger, providing structural support and increasing the capacity for nutrient and water transport. Secondary growth is typical in woody plants, while herbaceous plants primarily undergo primary growth.
268. The cambial activity in a plant results in the formation of:
ⓐ. Leaves and roots
ⓑ. Secondary xylem and secondary phloem
ⓒ. Root hairs and trichomes
ⓓ. Flowers and fruits
Correct Answer: Secondary xylem and secondary phloem
Explanation: Cambial activity results in the production of secondary xylem and secondary phloem. The cambium is a meristematic tissue that divides and forms new vascular tissue, increasing the plant’s diameter. Secondary xylem (wood) is produced toward the inside of the cambial ring, while secondary phloem is produced toward the outside. This process is essential for the thickening of the plant and allows for the transport of water, nutrients, and sugars.
269. Which of the following is true regarding the cambial ring in plants?
ⓐ. It is formed only in dicot plants and is responsible for primary growth
ⓑ. It remains inactive after the plant matures
ⓒ. It is responsible for the formation of secondary vascular tissues during secondary growth
ⓓ. It produces only xylem tissue for the plant
Correct Answer: It is responsible for the formation of secondary vascular tissues during secondary growth
Explanation: The cambial ring is a layer of meristematic tissue that forms between the primary xylem and phloem. It is responsible for secondary growth, producing secondary vascular tissues: secondary xylem (wood) and secondary phloem. This growth allows plants to increase in girth and support more vascular tissue as they mature. The cambium remains active throughout the life of the plant, producing new layers of vascular tissue every year.
270. In plants, the formation of the cambial ring and its activity leads to:
ⓐ. The elongation of the plant through apical meristem
ⓑ. The production of flowers and fruits
ⓒ. The thickening of the plant stem and roots
ⓓ. The formation of leaves and leaf primordia
Correct Answer: The thickening of the plant stem and roots
Explanation: The cambial ring is a key component of secondary growth in plants. It produces secondary xylem (wood) toward the inside and secondary phloem toward the outside. This thickens the plant’s stem and roots, allowing it to support more vascular tissue. Secondary growth, driven by the cambium, is essential for the development of woody plants and contributes to the plant’s ability to transport water, nutrients, and sugars over greater distances.
271. The difference between heartwood and sapwood is primarily:
ⓐ. Heartwood is the younger xylem, while sapwood is older
ⓑ. Sapwood is non-functional, while heartwood actively conducts water
ⓒ. Heartwood is the outer layer of the stem, while sapwood is inside
ⓓ. Heartwood contains dead xylem cells, while sapwood consists of living xylem cells
Correct Answer: Heartwood contains dead xylem cells, while sapwood consists of living xylem cells
Explanation: Heartwood and sapwood are two distinct parts of the xylem in woody plants. Heartwood is the inner portion of the xylem and consists of dead cells. These cells no longer conduct water but serve as a structural support for the tree. In contrast, sapwood is the outer part of the xylem and contains living cells that are actively involved in water conduction. The transition from sapwood to heartwood occurs as the older xylem cells die and become impregnated with substances like resins or tannins, which give heartwood its darker color and increase its durability.
272. The primary function of sapwood is to:
ⓐ. Store nutrients and sugars
ⓑ. Provide structural support for the plant
ⓒ. Conduct water and minerals from the roots to the leaves
ⓓ. Protect the plant from pathogens
Correct Answer: Conduct water and minerals from the roots to the leaves
Explanation: Sapwood is the functional part of the xylem that actively conducts water and dissolved minerals from the roots to the rest of the plant, particularly the leaves where photosynthesis occurs. The living cells in the sapwood are responsible for this transport, and they are critical to the plant’s ability to take up water and essential nutrients from the soil. As the tree ages, sapwood gradually becomes heartwood, losing its ability to conduct water but continuing to provide structural support to the plant.
273. The formation of heartwood occurs when:
ⓐ. Xylem cells die and become filled with resins or tannins
ⓑ. New vascular cambium cells divide and form more xylem and phloem
ⓒ. The plant stops conducting water through the xylem
ⓓ. The plant produces secondary phloem for nutrient transport
Correct Answer: Xylem cells die and become filled with resins or tannins
Explanation: Heartwood forms when the older xylem cells die and are filled with various organic compounds like resins, tannins, and other substances. These compounds help preserve the heartwood, making it more resistant to decay and insects. Unlike sapwood, which consists of living cells that actively transport water and nutrients, heartwood does not participate in conduction but provides structural integrity to the plant. The transition from sapwood to heartwood is a gradual process that occurs over time as the plant matures.
274. In a mature tree, heartwood is typically located:
ⓐ. At the outermost layers of the stem
ⓑ. Directly under the cambium, functioning in secondary growth
ⓒ. In the innermost part of the xylem, surrounded by sapwood
ⓓ. Between the epidermis and cortex for protection
Correct Answer: In the innermost part of the xylem, surrounded by sapwood
Explanation: In a mature tree, heartwood is located at the center of the stem, surrounded by sapwood. The heartwood consists of dead xylem cells that no longer participate in water conduction but provide structural support. Sapwood, which is located outside the heartwood, contains living xylem cells that actively transport water and nutrients. Over time, older xylem cells in the sapwood become converted into heartwood as the plant ages, and the transition is marked by the deposition of substances like resins and tannins that make the heartwood more durable.
275. The secondary phloem produced by the vascular cambium:
ⓐ. Is located outside the cambium and is responsible for transporting sugars
ⓑ. Remains dormant and does not participate in nutrient transport
ⓒ. Is involved in the formation of the cork and bark
ⓓ. Directly contributes to the formation of heartwood
Correct Answer: Is located outside the cambium and is responsible for transporting sugars
Explanation: The secondary phloem is produced by the vascular cambium, which is located between the xylem and phloem. Secondary phloem is located outside the cambium layer and is responsible for transporting sugars, hormones, and other organic compounds produced in the leaves. It plays a key role in moving the products of photosynthesis from the leaves to other parts of the plant. As the tree grows, new layers of secondary phloem are produced, although the inner layers may become inactive and contribute to the formation of bark or cork.
276. In woody plants, the vascular cambium is responsible for:
ⓐ. The formation of the epidermis and cortex
ⓑ. The production of new cells for root growth
ⓒ. The formation of secondary xylem and phloem for thickening
ⓓ. The formation of the central pith and vascular bundles
Correct Answer: The formation of secondary xylem and phloem for thickening
Explanation: The vascular cambium is a lateral meristem responsible for secondary growth in woody plants. It forms a continuous ring between the primary xylem and phloem and produces new cells that differentiate into secondary xylem (wood) and secondary phloem. This process leads to the thickening of the stem and roots, providing structural support for the plant. The vascular cambium is essential for the growth of trees and shrubs, allowing them to increase in girth over time.
277. Heartwood differs from sapwood in that:
ⓐ. It is younger and actively participates in water transport
ⓑ. It contains living cells and is involved in nutrient transport
ⓒ. It is composed of dead xylem cells filled with compounds like resins
ⓓ. It forms the outer layer of the plant stem
Correct Answer: It is composed of dead xylem cells filled with compounds like resins
Explanation: Heartwood is the innermost part of the xylem and consists of dead xylem cells that no longer participate in water conduction. These cells are filled with organic compounds such as resins and tannins, which increase the wood’s resistance to decay and pests. Unlike sapwood, which is active in water and nutrient transport, heartwood serves primarily as structural support, providing strength and durability to the plant. As a tree ages, the inner xylem cells become heartwood, and the outer layers of xylem remain functional as sapwood.
278. The vascular cambium is essential for secondary growth because it:
ⓐ. Produces cells that differentiate into new leaves
ⓑ. Creates a barrier to prevent water loss from the plant
ⓒ. Increases the length of the plant by dividing in the apical meristem
ⓓ. Forms new layers of vascular tissue (xylem and phloem) for thickening
Correct Answer: Forms new layers of vascular tissue (xylem and phloem) for thickening
Explanation: The vascular cambium is a lateral meristem that is responsible for the process of secondary growth. It divides to form secondary xylem (wood) and secondary phloem, which increase the plant’s girth over time. Secondary growth is crucial for the thickening of stems and roots, providing support and allowing the plant to grow larger. The vascular cambium plays a central role in the development of woody tissue, allowing trees and shrubs to become structurally stronger as they mature.
279. The heartwood is primarily responsible for:
ⓐ. Transporting water and minerals from the roots to the leaves
ⓑ. Facilitating the movement of gases through the plant
ⓒ. Conducting photosynthesis by storing sugars
ⓓ. Providing structural support and strength to the plant
Correct Answer: Providing structural support and strength to the plant
Explanation: Heartwood is the central, non-functional part of the xylem. It is composed of dead xylem cells that no longer conduct water, but instead serve as a structural component of the plant. The cells in heartwood are impregnated with substances like resins, which make the wood durable and resistant to decay. While it no longer participates in water transport, heartwood provides the plant with the necessary strength and stability to support its height and structure.
280. The transition from sapwood to heartwood involves:
ⓐ. The accumulation of minerals that provide the plant with nutrients
ⓑ. The deposition of compounds like tannins and resins that make the wood durable
ⓒ. The formation of new phloem to replace the old phloem
ⓓ. The splitting of cambial cells to form secondary vascular tissue
Correct Answer: The deposition of compounds like tannins and resins that make the wood durable
Explanation: The transition from sapwood to heartwood occurs when the older xylem cells in the sapwood die and become filled with organic compounds such as tannins, resins, and oils. These compounds make the wood more durable and resistant to decay, insects, and pathogens. This process not only marks the aging of xylem tissue but also gives heartwood its darker color and increased density. While sapwood is active in water conduction, heartwood provides structural support and is largely inactive in terms of transport.
281. The cork cambium is responsible for:
ⓐ. The formation of secondary xylem and phloem
ⓑ. The production of new epidermal cells for the plant
ⓒ. The production of cork and the formation of periderm
ⓓ. The synthesis of chlorophyll for photosynthesis
Correct Answer: The production of cork and the formation of periderm
Explanation: The cork cambium is a type of lateral meristem responsible for the production of cork, which forms the outer protective layer of the plant during secondary growth. As the plant grows, the epidermis becomes stretched and damaged, and the cork cambium produces a new layer of protective tissue called periderm. The periderm replaces the epidermis in mature plants and includes the cork, cork cambium, and phelloderm. The cork provides protection against physical damage, pathogens, and water loss, making the cork cambium essential for the plant’s long-term survival.
282. The periderm is composed of:
ⓐ. Cork, cork cambium, and phelloderm
ⓑ. The epidermis and cuticle
ⓒ. Xylem, phloem, and vascular cambium
ⓓ. Primary growth tissues that enable leaf expansion
Correct Answer: Cork, cork cambium, and phelloderm
Explanation: The periderm is the protective tissue that replaces the epidermis in woody plants as they undergo secondary growth. It is made up of three components: cork, cork cambium, and phelloderm. The cork forms the outer layer, providing a barrier against environmental stress, pathogens, and water loss. The cork cambium is the meristematic tissue that generates the cork and phelloderm, while the phelloderm is the inner layer of the periderm, responsible for storing nutrients and assisting with plant protection. The periderm is crucial for the protection of the plant’s internal tissues during the growth process.
283. The primary function of lenticels in woody plants is to:
ⓐ. Facilitate photosynthesis by absorbing sunlight
ⓑ. Allow for gas exchange between the plant and the environment
ⓒ. Provide structural support to the plant’s stem
ⓓ. Protect the plant from excessive water loss
Correct Answer: Allow for gas exchange between the plant and the environment
Explanation: Lenticels are small, spongy openings in the periderm that allow for gas exchange between the plant’s internal tissues and the external environment. These structures are especially important in woody plants, as they help facilitate the movement of oxygen and carbon dioxide into and out of the plant, particularly in the stem and roots. Since the bark layer formed by the periderm is generally impermeable to gases, lenticels provide the necessary openings for respiration and other metabolic processes. Their function is vital for maintaining cellular respiration in the plant as it matures.
284. Cork cambium is different from vascular cambium in that:
ⓐ. Cork cambium produces cork and periderm, while vascular cambium produces secondary xylem and phloem
ⓑ. Cork cambium is responsible for secondary growth in leaves, while vascular cambium is involved in root growth
ⓒ. Cork cambium produces xylem and phloem, while vascular cambium produces cork
ⓓ. Cork cambium is found only in roots, while vascular cambium is found in stems
Correct Answer: Cork cambium produces cork and periderm, while vascular cambium produces secondary xylem and phloem
Explanation: The cork cambium and vascular cambium are both involved in secondary growth but serve different functions. The cork cambium produces cork and the periderm, which form protective layers around the plant as it matures. On the other hand, the vascular cambium is responsible for producing secondary xylem (wood) and secondary phloem, contributing to the thickening of the stem and root. While both cambiums are lateral meristems, their roles are distinct, with the cork cambium providing external protection and the vascular cambium contributing to internal growth.
285. In woody plants, lenticels are primarily responsible for:
ⓐ. Providing structural support during secondary growth
ⓑ. Allowing water to be absorbed from the soil
ⓒ. Enabling gas exchange in stems and roots
ⓓ. Producing new vascular tissue for growth
Correct Answer: Enabling gas exchange in stems and roots
Explanation: Lenticels are specialized pores that form in the periderm, allowing for gas exchange between the internal tissues of the plant and the surrounding environment. They are especially important in woody plants, where the periderm (including cork) becomes impermeable to gases. Since these plants continue to need oxygen for respiration and release carbon dioxide, lenticels provide essential openings for these gases to diffuse in and out of the plant. Lenticels allow the plant to perform respiration and other metabolic processes that require gas exchange, even after the formation of the protective bark.
286. The cork produced by the cork cambium serves primarily to:
ⓐ. Enhance the plant’s ability to absorb water
ⓑ. Store sugars and nutrients for the plant
ⓒ. Facilitate the movement of gases within the plant
ⓓ. Protect the plant from physical damage, pathogens, and water loss
Correct Answer: Protect the plant from physical damage, pathogens, and water loss
Explanation: The cork produced by the cork cambium forms the outermost protective layer of the plant. It serves several critical functions: protecting the plant from physical damage, preventing water loss through transpiration, and providing a barrier against pathogens and environmental stresses. As the plant ages and undergoes secondary growth, the epidermis is replaced by the cork, which is much thicker and more durable. The cork is rich in suberin, a waxy substance that helps waterproof the plant and protect its internal tissues.
287. The formation of the periderm involves:
ⓐ. The differentiation of vascular tissue into xylem and phloem
ⓑ. The continuous division of the epidermis to form a new protective layer
ⓒ. The splitting of the primary root for secondary growth
ⓓ. The activity of the cork cambium producing cork and phelloderm
Correct Answer: The activity of the cork cambium producing cork and phelloderm
Explanation: The formation of the periderm occurs during secondary growth when the cork cambium produces cork and phelloderm. The cork forms the outer protective layer, while the phelloderm is a thin layer of living cells beneath the cork. Together, these tissues replace the original epidermis, which becomes damaged as the plant grows. The periderm serves to protect the plant from physical damage, water loss, and pathogen invasion, and it plays an essential role in the survival of woody plants.
288. Lenticels are found in the:
ⓐ. Cortex of the root for water absorption
ⓑ. Epidermis of the leaf for photosynthesis
ⓒ. Periderm of woody stems and roots for gas exchange
ⓓ. Xylem and phloem for nutrient transport
Correct Answer: Periderm of woody stems and roots for gas exchange
Explanation: Lenticels are small, spongy openings found in the periderm of woody stems and roots. They provide channels for the exchange of gases such as oxygen and carbon dioxide, which are necessary for cellular respiration and other metabolic processes. Since the periderm, which includes the cork, is impermeable to gases, lenticels are crucial for ensuring that the plant’s internal tissues receive sufficient oxygen and can expel carbon dioxide, even after the epidermis has been replaced by the protective cork.
289. The function of the cork cambium in secondary growth is to:
ⓐ. Form new xylem and phloem for increased water and nutrient transport
ⓑ. Produce protective cork tissue to replace the epidermis
ⓒ. Facilitate gas exchange between the plant and the environment
ⓓ. Provide structural support to the plant by thickening the stem
Correct Answer: Produce protective cork tissue to replace the epidermis
Explanation: The cork cambium is responsible for producing the cork tissue, which forms part of the periderm. The cork replaces the epidermis as the plant matures and undergoes secondary growth. This protective layer helps prevent water loss, protects against physical damage, and defends against pathogens. As the plant grows in diameter, the cork cambium continues to produce new layers of cork, ensuring that the plant is well-protected as it ages.
290. The periderm is formed as a result of:
ⓐ. The activity of the epidermis in the outermost layer of the plant
ⓑ. The division of cells in the cambium layer between the xylem and phloem
ⓒ. The activity of the cork cambium, producing cork and phelloderm
ⓓ. The differentiation of vascular tissue into wood and bark
Correct Answer: The activity of the cork cambium, producing cork and phelloderm
Explanation: The periderm forms during secondary growth in woody plants. It consists of three layers: cork, cork cambium, and phelloderm. The cork cambium is the meristematic tissue responsible for producing the cork and phelloderm. The cork forms the outermost protective layer of the plant, while the phelloderm is a layer of living cells inside the cork. The periderm replaces the epidermis as the plant grows in diameter, providing protection from physical damage, water loss, and pathogen invasion.
291. Annual rings in trees are formed by:
ⓐ. The expansion of vascular cambium during spring and summer
ⓑ. The secondary growth of leaves and branches
ⓒ. The alternation of spring wood and autumn wood in the xylem
ⓓ. The accumulation of starch in the cambium layer
Correct Answer: The alternation of spring wood and autumn wood in the xylem
Explanation: Annual rings in trees are the result of the alternation between spring wood and autumn wood formed during secondary growth. In spring, the vascular cambium produces large, thin-walled xylem cells that are capable of transporting water more efficiently. As the growing season progresses into autumn, the xylem cells become smaller and thicker-walled, contributing to the formation of autumn wood. These alternating layers form the annual rings, with one complete cycle of spring and autumn wood marking each year of growth. The width of the rings can provide information about the plant’s age and the environmental conditions during different years.
292. Spring wood is characterized by:
ⓐ. Large, thin-walled xylem cells that are produced early in the growing season
ⓑ. Small, thick-walled xylem cells that are produced later in the growing season
ⓒ. Cells that are responsible for nutrient storage and not for water transport
ⓓ. A lack of vascular cambium activity during the warmer months
Correct Answer: Large, thin-walled xylem cells that are produced early in the growing season
Explanation: Spring wood is formed during the early part of the growing season when the vascular cambium is active and producing large, thin-walled xylem cells. These cells are efficient at transporting water, which is crucial during the period of rapid growth in spring. The wide diameter of the xylem vessels in spring wood allows for greater water conduction. The cells are thinner and less dense than those formed in the autumn, and they contribute to the early phase of the annual growth cycle.
293. Autumn wood is distinguished by:
ⓐ. Large, thin-walled xylem cells that are formed early in the growing season
ⓑ. The formation of phloem rather than xylem
ⓒ. A greater number of vessel elements compared to spring wood
ⓓ. Thick, dark-walled xylem cells produced during the end of the growing season
Correct Answer: Thick, dark-walled xylem cells produced during the end of the growing season
Explanation: Autumn wood is produced later in the growing season when the cambium activity slows down. The xylem cells formed during this time are smaller in diameter and have thicker, darker walls compared to the spring wood cells. These cells are less efficient in water conduction but provide structural support to the tree. The formation of autumn wood marks the end of the growing season, and its smaller, thicker-walled cells help the tree withstand the cold months by providing added strength and protection against mechanical stress and dehydration.
294. Annual rings can provide information about:
ⓐ. The age of the plant only
ⓑ. The tree’s water consumption over its lifetime
ⓒ. The tree’s age and the environmental conditions during the growing season
ⓓ. The soil’s nutrient content in the root zone
Correct Answer: The tree’s age and the environmental conditions during the growing season
Explanation: Annual rings in trees not only provide the age of the tree but also offer insights into the environmental conditions during each growing season. The width of the rings can indicate the availability of water, nutrients, and sunlight. For example, wider rings often signify favorable growing conditions with ample water and nutrients, while narrower rings may indicate a period of drought or stress. The alternating spring and autumn wood also provide clues about the length of the growing season and the climate during that year.
295. The difference between spring wood and autumn wood is mainly based on:
ⓐ. The type of cells produced by the cambium
ⓑ. The thickness of the xylem cell walls and the size of the vessels
ⓒ. The type of nutrients transported by the phloem
ⓓ. The growth rate of the vascular cambium
Correct Answer: The thickness of the xylem cell walls and the size of the vessels
Explanation: The primary difference between spring wood and autumn wood lies in the characteristics of the xylem cells. Spring wood is made up of large, thin-walled xylem cells, which are produced during the early growing season when water is abundant. These large vessels are efficient at conducting water. In contrast, autumn wood is composed of smaller, thicker-walled xylem cells that are produced later in the growing season when growth slows down. These smaller vessels are better suited to providing structural support rather than water transport.
296. The width of annual rings in a tree is influenced by:
ⓐ. The temperature of the environment during the growing season
ⓑ. The amount of light available during the day
ⓒ. The availability of water and nutrients
ⓓ. The age of the tree
Correct Answer: The availability of water and nutrients
Explanation: The width of annual rings is primarily influenced by environmental factors such as the availability of water and nutrients. In years when water and nutrients are abundant, the tree grows rapidly, producing wider rings with larger xylem vessels. Conversely, in years with limited water or nutrients, the tree’s growth slows down, resulting in narrower rings. These variations in ring width can provide valuable information about the climate and growing conditions during each year of the tree’s life, making annual rings an important indicator of environmental changes over time.
297. In regions with harsh winters, annual rings tend to be:
ⓐ. Narrow, due to limited growth during the colder months
ⓑ. Very wide, due to rapid growth during the short growing season
ⓒ. Consistently thin, regardless of the weather conditions
ⓓ. Thick in the center and thin at the edges
Correct Answer: Narrow, due to limited growth during the colder months
Explanation: In regions with harsh winters, annual rings tend to be narrow due to the short growing season and reduced growth during the cold months. The tree’s growth is limited by the availability of water, sunlight, and favorable temperatures. As a result, the vascular cambium produces fewer and smaller xylem cells, leading to the formation of narrow annual rings. These narrower rings can indicate colder climates where the growing season is shorter, and the tree has less time to grow.
298. The formation of annual rings is a result of:
ⓐ. The difference in the size of the vascular cambium cells
ⓑ. The differentiation of ground tissue into vascular tissue
ⓒ. The expansion of the epidermis as the plant matures
ⓓ. The periodic activity of the vascular cambium during the growing season
Correct Answer: The periodic activity of the vascular cambium during the growing season
Explanation: The formation of annual rings is the result of the periodic activity of the vascular cambium. During the growing season, the cambium produces new layers of secondary xylem and phloem. In spring, the cambium forms larger xylem cells, known as spring wood, while in autumn, it forms smaller, thicker-walled xylem cells, known as autumn wood. The alternating production of these different types of xylem creates the distinct annual rings, which reflect the plant’s growth patterns over time.
299. The heartwood of a tree is formed when:
ⓐ. The vascular cambium produces new phloem and xylem in the stem
ⓑ. The older xylem cells become filled with substances like tannins
ⓒ. The cambium ceases to produce secondary xylem
ⓓ. The outer xylem cells die and form a protective layer
Correct Answer: The older xylem cells become filled with substances like tannins
Explanation: The heartwood forms when the older xylem cells, located in the center of the tree, die and become filled with substances such as tannins, resins, and other compounds. These substances serve to harden the wood, making it more durable and resistant to decay, insects, and pathogens. While the heartwood no longer conducts water, it provides structural support to the tree, helping it maintain stability as it grows taller. The transition from sapwood to heartwood is a natural part of the tree’s aging process.
300. The difference in the appearance of spring wood and autumn wood can be used to determine:
ⓐ. The plant’s age only
ⓑ. The tree’s ability to transport water
ⓒ. The environmental conditions during the growing season
ⓓ. The presence of secondary growth in the plant
Correct Answer: The environmental conditions during the growing season
Explanation: The difference in the appearance of spring wood and autumn wood can provide valuable insights into the environmental conditions during the growing season. Spring wood is characterized by larger, thinner-walled xylem cells, indicating faster growth when water and nutrients are abundant. Autumn wood, on the other hand, is composed of smaller, thicker-walled xylem cells, formed when growth slows down due to reduced water availability or other environmental factors. By examining the width and characteristics of these annual rings, we can infer the climate and growing conditions of each year, such as periods of drought or favorable weather for plant growth.