401. Two plants both produce capsules.
| Feature | Plant P | Plant Q |
|---|
| Corolla | Five united valvate petals | Five free twisted petals |
| Stamens | Five and epipetalous | Numerous, monadelphous and monothecous |
| Ovary | Bicarpellary and axile | Multicarpellary and axile |
Which conclusion is correct?
ⓐ. Both plants must belong to one family because their fruit type and placentation agree.
ⓑ. P fits Solanaceae and Q fits Malvaceae, while a shared capsule is not family-specific.
ⓒ. P is Malvaceae and Q is Solanaceae because stamen number does not matter.
ⓓ. Both plants are Brassicaceae because capsules always arise from parietal ovaries.
Correct Answer: P fits Solanaceae and Q fits Malvaceae, while a shared capsule is not family-specific.
Explanation: Plant P has a united valvate corolla and five stamens attached to the petals, a typical Solanaceae pattern. Its bicarpellary axile ovary also supports that assignment. Plant Q has free twisted petals, numerous filaments united into a monadelphous column and monothecous anthers, identifying Malvaceae. Its multicarpellary axile ovary is consistent with that family. Both families can produce capsules, so capsule identity alone cannot separate them. Axile placentation is also shared and must be interpreted with corolla and androecial characters. Brassicaceae has parietal placentation and commonly forms a siliqua or silicula rather than the floral patterns shown. The table demonstrates why family identification requires a diagnostic combination instead of reliance on one shared fruit type. Capsule formation and axile placentation are shared, while corolla fusion, stamen organisation and carpel number provide the decisive separation.
402. An Asteraceae floret is taken from the margin of a capitulum. It has a ligulate zygomorphic corolla, but its androecium and gynoecium are damaged beyond recognition. Which conclusion is most justified?
ⓐ. It is a ray floret, but the available evidence cannot establish whether it was female or neuter.
ⓑ. It is necessarily a female ray floret because every marginal floret possesses a functional gynoecium.
ⓒ. It is necessarily a neuter ray floret because a ligulate corolla excludes functional reproductive whorls.
ⓓ. It is a bisexual disc floret because both ray and disc florets have the same position and corolla form.
Correct Answer: It is a ray floret, but the available evidence cannot establish whether it was female or neuter.
Explanation: Marginal position together with a ligulate, zygomorphic corolla identifies the specimen as a ray floret of an Asteraceae capitulum. These characters distinguish it from a typical disc floret, which lies centrally and commonly has a tubular, actinomorphic corolla. The supplied evidence does not, however, reveal the sexuality of the ray floret. Ray florets may be female, with a functional gynoecium, or neuter, with ineffective reproductive whorls. Because the androecium and gynoecium are damaged, neither condition can be verified from the specimen. Corolla shape and position establish floret type, but they do not by themselves prove whether a functional gynoecium was present. The strongest conclusion therefore separates the justified identification of a ray floret from the unsupported inference about its sexuality.
403. All peripheral ray florets are experimentally removed from a young sunflower head, but the central disc florets, common receptacle and involucral bracts remain intact. Which prediction is most accurate?
ⓐ. The remaining structure becomes a solitary flower because only one floret type is present.
ⓑ. The structure becomes a grass spikelet because the outer florets are absent.
ⓒ. Every disc floret becomes an involucral bract.
ⓓ. It remains a capitulum of disc florets but loses its peripheral ligulate zone.
Correct Answer: It remains a capitulum of disc florets but loses its peripheral ligulate zone.
Explanation: Capitulum identity depends on the organisation of multiple sessile florets on a common receptacle surrounded by involucral bracts. Removal of one floret category does not collapse the remaining disc florets into one flower. Each disc floret retains its own floral organs and inferior ovary, so the head remains a multi-flowered inflorescence. The conspicuous peripheral ligulate region disappears; that zone had been formed by the ray florets. Nothing in the treatment produces glumes, lemma or palea, so the structure cannot become a Poaceae spikelet. Involucral bracts also retain their identity outside the head and do not arise by transformation of disc florets. The prediction separates the defining architecture of the capitulum from the optional presence of differentiated peripheral ray florets.
404. A grass mutant develops anthers that remain rigidly fixed instead of being versatile, and its stigmas become smooth rather than feathery. All other floral parts are normal. Which pair of Poaceae characters is specifically altered?
ⓐ. Lemma enclosure and palea position
ⓑ. Lodicule number and ovary position
ⓒ. Anther attachment and stigma form
ⓓ. Glume number and caryopsis-wall fusion
Correct Answer: Anther attachment and stigma form
Explanation: Versatile describes the manner in which a grass anther is attached to its filament, allowing it to move readily. Replacing that condition with rigid attachment directly alters anther organisation. A feathery stigma possesses numerous branches and is a characteristic receptive structure of the grass flower. Loss of those branches changes stigma form. The mutation does not affect the outer spikelet bracts, so the glumes, lemma and palea remain normal. Lodicule number and superior ovary position are also stated to be unchanged. Caryopsis-wall fusion is a later fruit character involving the pericarp and seed coat. The altered traits occur in two different reproductive organs, but both belong to the standard Poaceae floral description: versatile anthers in the androecium and feathery stigmas in the gynoecium.
405. A floral record gives the formula \(\oplus\,K_{(5)}\,C_{(5)}\,A_5\,\underline{G}_{(2)}\) but labels the flower as unisexual. Which correction is required?
ⓐ. The flower must be asymmetric because both accessory whorls are fused.
ⓑ. The flower must be female because the gynoecium contains two carpels.
ⓒ. The presence of both \(A\) and \(G\) shows that the flower is bisexual.
ⓓ. The formula must represent a male flower because \(A_5\) precedes \(G_{(2)}\).
Correct Answer: The presence of both \(A\) and \(G\) shows that the flower is bisexual.
Explanation: The formula includes an androecium, represented by \(A_5\), and a gynoecium, represented by \(G_{(2)}\). Presence of both reproductive whorls in the same flower establishes bisexuality. Sexuality depends on the simultaneous presence of functional male and female whorls, so the two symbols must be considered together rather than read in isolation. Their order in the formula follows the usual outside-to-inside floral sequence and does not make the flower male. Brackets around the calyx, corolla and gynoecium indicate fusion within those whorls; they do not determine sexuality or symmetry. The symbol \(\oplus\) already records actinomorphy. The gynoecium contains two fused carpels and is superior, but that does not make the flower exclusively female while five stamens are also present. The written label is inconsistent with the symbolic record and should be corrected to bisexual. Sexuality is read from the presence of both reproductive whorls, not from symmetry or the degree of fusion in accessory whorls.
406. Sample P contains \(8\) Brassicaceae flowers, each with \(A_{2+4}\). Sample Q contains \(8\) Solanaceae flowers, each with \(A_5\). How do their total stamen counts compare?
ⓐ. P has \(16\), Q has \(40\); Q exceeds P by \(24\).
ⓑ. P has \(40\), Q has \(40\); the totals are equal.
ⓒ. P has \(48\), Q has \(48\); the totals are equal.
ⓓ. P has \(48\), Q has \(40\); P exceeds Q by \(8\).
Correct Answer: P has \(48\), Q has \(40\); P exceeds Q by \(8\).
Explanation: In Brassicaceae, \(A_{2+4}\) represents six stamens per flower: two short and four long. For Sample P,
\[
8\,\text{flowers}\times(2+4)\,\text{stamens per flower} =8\times6=48\,\text{stamens}
\]
A typical Solanaceae flower has \(A_5\), so Sample Q contains
\[
8\,\text{flowers}\times5\,\text{stamens per flower} =40\,\text{stamens}
\]
The difference is
\[
48-40=8\,\text{stamens}
\]
The \(2+4\) notation must be interpreted as two length classes within one six-stamen androecium, not as two alternative counts. Both samples contain the same number of flowers, so the comparison reflects the per-flower androecial plan. Sample P has \(48\) stamens, Sample Q has \(40\), and the Brassicaceae sample exceeds the Solanaceae sample by \(8\). The comparison also shows that equal flower counts do not imply equal total stamen counts when the families have different androecial formulas. Family-level stamen number directly produces the numerical difference between the two equal-sized samples.
407. A formula shows \(C_{(5)}\) and a connecting line between \(C\) and \(A_5\). Its floral diagram instead shows five completely separate petals and stamens with no attachment to the petals. Which evaluation is correct?
ⓐ. The diagram conflicts with both petal fusion and epipetalous stamen attachment.
ⓑ. The formula and diagram agree because both contain five petals and five stamens.
ⓒ. Only the indicated ovary position differs between the formula and diagram.
ⓓ. Both the parentheses and connecting line indicate fusion among the five stamens.
Correct Answer: The diagram conflicts with both petal fusion and epipetalous stamen attachment.
Explanation: Brackets in \(C_{(5)}\) show that the five petals are united, producing a gamopetalous corolla. The connecting line between the corolla and androecium records adhesion of stamens to petals, an epipetalous condition. The diagram contradicts the first relation by drawing five completely free petals and contradicts the second by showing no stamen–petal attachment. Agreement in member number does not repair disagreement in fusion and adhesion. The brackets do not describe stamen cohesion, and no information about ovary position is supplied in the stated mismatch. Formulae and floral diagrams are complementary representations of one flower, so they must agree not only on counts but also on the relationships within and between whorls. The same five-membered count can appear in both records while the relationship information remains contradictory. A consistent diagram would show a corolla tube and attachment of the stamens to that tube.
408. An unknown plant is a small tree rather than an herb or shrub. It has alternate simple exstipulate leaves, a united valvate corolla, five epipetalous stamens and a superior bicarpellary ovary with axile placentation. Which conclusion is justified?
ⓐ. Woody habit excludes Solanaceae even when the flower has its diagnostic combination.
ⓑ. Small-tree habit does not exclude Solanaceae, and the floral characters support it.
ⓒ. Woody habit proves Poaceae because every tree-like flowering plant is a monocot.
ⓓ. Tree habit alone proves Malvaceae despite the conflicting corolla and stamen characters.
Correct Answer: Small-tree habit does not exclude Solanaceae, and the floral characters support it.
Explanation: Solanaceae consists mainly of herbs and shrubs, but small trees may occur rarely. The unusual habit should be treated as a qualifier rather than an absolute exclusion. The reproductive characters provide stronger family evidence. A united valvate corolla, five stamens attached to the petals and a superior bicarpellary ovary with axile placentation form a characteristic Solanaceae combination. Alternate simple exstipulate leaves also agree with the usual vegetative pattern. Poaceae has grass-like culms, sheathing parallel-veined leaves and spikelets, while Malvaceae typically has stipulate leaves, free twisted petals and numerous monadelphous stamens. The correct inference weighs a rare permitted habit against several highly diagnostic floral observations and retains Solanaceae as the supported classification.
409. A racemose inflorescence already has older flowers near its base and younger buds toward its apex. The terminal growing region is then cut off. Which conclusion is most accurate?
ⓐ. The inflorescence immediately becomes cymose because its axis can no longer elongate.
ⓑ. All basal flowers reverse age order and become younger than the apical buds after cutting.
ⓒ. Every lateral flower changes into a terminal flower when the main apex is removed.
ⓓ. Apical growth stops, but the existing acropetal racemose pattern does not become cymose.
Correct Answer: Apical growth stops, but the existing acropetal racemose pattern does not become cymose.
Explanation: The inflorescence developed as racemose because its main apex remained active while lateral flowers were initiated in acropetal order. Removing that apex later prevents continued elongation and addition of younger flowers, but it does not change the developmental origin or established age sequence of the existing flowers. A true cymose inflorescence becomes determinate because the main axis naturally terminates in a flower, with subsequent branching and a basipetal or centrifugal age pattern. Accidental removal of an indeterminate apex is not equivalent to normal terminal-flower formation. The older basal flowers remain older, and lateral flowers do not become terminal structures. The treatment changes future growth capacity while preserving evidence of the original racemose organisation.
410. A mutation changes a flower from having several valid radial symmetry planes to having only one plane that divides it into equal halves. The flower still has both reproductive whorls, five members in each outer whorl, a subtending bract and an unchanged superior ovary. Which conclusion is correct?
ⓐ. Sexuality changes from bisexual to unisexual, while the other listed traits remain unchanged.
ⓑ. Merosity changes from pentamerous to trimerous, while the other listed traits remain unchanged.
ⓒ. Symmetry changes from actinomorphic to zygomorphic, while the other listed traits remain unchanged.
ⓓ. Ovary position changes from superior to inferior, while the other listed traits remain unchanged.
Correct Answer: Symmetry changes from actinomorphic to zygomorphic, while the other listed traits remain unchanged.
Explanation: Several radial planes producing equal halves define actinomorphy, while only one valid plane defines zygomorphy. The mutation changes the symmetry category. The remaining observations concern independent descriptors. Presence of both androecium and gynoecium preserves bisexuality. Five members in each relevant whorl preserve pentamery. The subtending bract maintains the bracteate condition, and unchanged insertion of floral whorls below the ovary preserves its superior position. None of these characters is logically determined by symmetry alone. Real flowers often combine zygomorphy with bisexuality and a superior ovary, as in Fabaceae. The case demonstrates why a floral description must record symmetry, sexuality, merosity, bract condition and ovary position separately instead of treating them as one linked property.
411. Match each green structure with its correct identity. Each Column II entry is used once.
| Column I | Column II |
|---|
| P. One leaf-like structure subtending an individual flower | 1. Involucre |
| Q. A series of bracteoles outside the calyx of Hibiscus | 2. Bract |
| R. A ring of bracts surrounding an entire Asteraceae capitulum | 3. Epicalyx |
ⓐ. P-3, Q-1, R-2
ⓑ. P-2, Q-3, R-1
ⓒ. P-1, Q-2, R-3
ⓓ. P-2, Q-1, R-3
Correct Answer: P-2, Q-3, R-1
Explanation: Structure P subtends one individual flower and is a bract, giving P-2. Structure Q consists of bracteoles arranged outside the true calyx of Hibiscus and forms an epicalyx, so Q-3. Structure R surrounds an entire capitulum rather than one floret. Collectively, those bracts form an involucre, giving R-1. All three structures may be green and leaf-like, so colour alone cannot distinguish them. Their position and the organisational level they subtend are decisive. A bract is associated with one flower or inflorescence branch, an epicalyx forms an additional series outside a flower’s calyx, and an involucre encloses the whole Asteraceae head containing many florets. The correct mapping preserves these nested positional relations.
412. Roots arising from lower stem nodes of a maize plant normally provide additional support. A mutation prevents them from becoming thick and mechanically effective, but they still originate from the same stem nodes. They should be described as:
ⓐ. stem branches because they arise from nodes
ⓑ. tap roots because their supporting function has been lost
ⓒ. adventitious roots with reduced stilt-root support
ⓓ. fibrous roots formed directly from the persistent radicle
Correct Answer: adventitious roots with reduced stilt-root support
Explanation: Root category is determined by origin, while modification is determined by specialised structure and function. These roots continue to arise from lower stem nodes, a non-radicular origin, so they remain adventitious roots. In normal maize, their oblique growth and mechanical role identify them as stilt roots. The mutation reduces that supporting specialisation but does not convert the organs into tap roots or stem branches. Tap roots arise from a persistent radicle, and a fibrous system involves numerous roots replacing the primary root near the stem base. Although the roots arise from stem nodes, their root organisation remains distinct from a branch. The correct description retains adventitious identity while recognising that the characteristic stilt-root modification has become weak or incomplete.
413. Assertion: A capsule fruit alone cannot reliably distinguish Solanaceae from Malvaceae.
Reason: Both families may produce capsules, but they differ strongly in corolla fusion, stamen organisation and carpel number.
ⓐ. Both Assertion and Reason are true, and Reason correctly explains Assertion
ⓑ. Both Assertion and Reason are true, but Reason does not explain Assertion
ⓒ. Assertion is true, but Reason is false and cannot explain Assertion
ⓓ. Assertion is false, but Reason is true and cannot explain Assertion
Correct Answer: Both Assertion and Reason are true, and Reason correctly explains Assertion
Explanation: The Assertion is true because capsule formation occurs in members of both Solanaceae and Malvaceae. Fruit type alone would leave more than one family possibility. The Reason is also true and explains how the ambiguity can be resolved. Solanaceae commonly has a united valvate corolla and five epipetalous stamens associated with a bicarpellary ovary. Malvaceae commonly has five free twisted petals, numerous monadelphous stamens with monothecous anthers and a multicarpellary ovary. These independent floral differences provide a much stronger diagnosis than the shared capsule. The Reason directly explains why the fruit character is insufficient by itself and identifies the kinds of additional evidence required. Family classification should rely on a decisive combination rather than a single overlapping feature.
414. A floral diagram shows an epigynous flower in which the thalamus encloses the ovary and the other whorls arise above it. The accompanying formula incorrectly uses \(\underline{G}_{(2)}\). Which correction is required?
ⓐ. Replace \(G\) with \(A\) because an inferior ovary belongs to the androecium.
ⓑ. Replace the underline with an overline while retaining \(G_{(2)}\).
ⓒ. Remove the brackets because every inferior ovary is monocarpellary.
ⓓ. Replace \(G_{(2)}\) with \(G_1\) and retain the underline.
Correct Answer: Replace the underline with an overline while retaining \(G_{(2)}\).
Explanation: The thalamus encloses the ovary and the other floral whorls arise above it, establishing an epigynous flower with an inferior ovary. In the stated floral-formula convention, an overline associated with \(G\) denotes the inferior position, whereas an underline denotes a superior ovary. The brackets around the subscript \(2\) carry separate information: two carpels are represented and are fused, producing a bicarpellary syncarpous gynoecium. Correcting ovary position does not require changing carpel number, fusion or the gynoecial symbol. Changing the carpel number would introduce an unsupported alteration. The formula should retain \(G_{(2)}\) and replace only the underline with an overline. This is a local correction: the ovary-position line changes, while the brackets continue to record syncarpy. This repair keeps the symbolic record aligned with the spatial relation shown in the floral diagram: surrounding and fused thalamic tissue places the remaining whorls above the ovary.
415. Two one-seeded dry fruits are dissected.
| Feature | Fruit P | Fruit Q |
|---|
| Ovary of origin | Inferior | Superior |
| Persistent structure | Pappus may remain | No pappus |
| Pericarp and seed coat | Remain distinguishable | Fused |
Which identification is correct?
ⓐ. P is an Asteraceae cypsela, and Q is a Poaceae caryopsis.
ⓑ. P is a Poaceae caryopsis, and Q is an Asteraceae cypsela.
ⓒ. Both are caryopses because each contains one seed.
ⓓ. Both are cypselas because each is dry and indehiscent.
Correct Answer: P is an Asteraceae cypsela, and Q is a Poaceae caryopsis.
Explanation: Fruit P develops from an inferior ovary and may retain a pappus derived from the modified calyx. These characters identify a cypsela of Asteraceae. Fruit Q develops from a superior one-ovulate ovary and shows fusion of the pericarp with the seed coat, the defining covering relation of a Poaceae caryopsis. The shared one-seeded, dry and indehiscent condition is not sufficient to make the fruits identical. Their ovary positions and fruit–seed wall relationships record different developmental origins. Pappus provides additional evidence for the Asteraceae fruit, while pericarp–seed coat fusion provides decisive evidence for the grass grain. The table separates two superficially similar fruits by tracing floral origin and mature covering organisation. The two fruits are separated by ovary position, pappus and wall–coat fusion even though both are dry and one-seeded.
416. An unknown plant has a compound leaf whose terminal leaflet is modified into a tendril. An axillary bud occurs only at the base of the whole leaf. Its flower has a standard, two wings and two keel petals, ten stamens arranged as \(9+1\), and a superior monocarpellary ovary with marginal placentation. Which conclusion is correct?
ⓐ. The tendril is a stem branch, and the plant belongs to Solanaceae.
ⓑ. Each leaflet is a complete leaf, and the plant belongs to Brassicaceae.
ⓒ. The tendril is a root modification, and the plant belongs to Poaceae.
ⓓ. The tendril is leaf-derived, and the plant belongs to Fabaceae.
Correct Answer: The tendril is leaf-derived, and the plant belongs to Fabaceae.
Explanation: The axillary bud occurs at the base of the complete compound leaf rather than at the base of each leaflet. This establishes that the terminal tendril occupies a leaflet position within one leaf and is leaf-derived, not a stem branch or root. The floral evidence independently identifies Fabaceae. A standard, two wings and two keel petals form a papilionaceous corolla with vexillary organisation. The \(9+1\) stamen arrangement is diadelphous, and the superior monocarpellary ovary with marginal placentation is characteristic of the family. The evidence links vegetative organ identity with reproductive classification. Both lines of evidence converge: a modified leaf part assists climbing, while the flower and gynoecium establish Fabaceae membership.
417. A temperate-region herb has alternate exstipulate leaves, five united valvate petals, five epipetalous stamens and a superior bicarpellary ovary with axile placentation. A collector rejects Solanaceae solely because the plant was not found in a tropical region. Which evaluation is correct?
ⓐ. The rejection is valid because Solanaceae is restricted to tropical regions regardless of floral characters.
ⓑ. The rejection is invalid because the range includes temperate regions and the floral traits fit Solanaceae.
ⓒ. The rejection is valid because every temperate solanaceous flower must have free petals and free stamens.
ⓓ. The rejection is invalid only if the plant also shows fibrous roots and parallel-veined leaves.
Correct Answer: The rejection is invalid because the range includes temperate regions and the floral traits fit Solanaceae.
Explanation: Solanaceae is distributed through tropical, subtropical and temperate regions, so occurrence in a temperate area cannot exclude the family. The floral evidence provides a much stronger basis for classification. Five united valvate petals, five stamens attached to the corolla and a superior bicarpellary syncarpous ovary with axile placentation form a characteristic Solanaceae combination. Alternate exstipulate leaves also agree with the common vegetative pattern. Geographic location may support ecological interpretation, but it should not override a diagnostic set of reproductive characters when the family has a broad distribution. Free petals would conflict with the typical gamopetalous Solanaceae corolla, and root-system type is not the condition that determines whether a temperate specimen can belong to the family.
418. An older herbarium register lists Cruciferae, Leguminosae, Compositae and Gramineae in that order. Which sequence gives their accepted equivalent family names?
ⓐ. Fabaceae, Brassicaceae, Poaceae and Asteraceae
ⓑ. Brassicaceae, Asteraceae, Fabaceae and Poaceae
ⓒ. Malvaceae, Fabaceae, Asteraceae and Solanaceae
ⓓ. Brassicaceae, Fabaceae, Asteraceae and Poaceae
Correct Answer: Brassicaceae, Fabaceae, Asteraceae and Poaceae
Explanation: Cruciferae is the traditional name corresponding to Brassicaceae, the family characterised by cruciform petals and a tetradynamous androecium. Leguminosae corresponds to Fabaceae, recognised by its papilionaceous corolla, commonly diadelphous stamens and legume fruit. Compositae is the traditional equivalent of Asteraceae, whose many florets are organised into a capitulum and whose fruit is a cypsela. Gramineae corresponds to Poaceae, the grass family characterised by culms, spikelets, lodicules and caryopsis fruits. The names within each pair refer to the same family rather than to closely related but separate families. Recognising both naming systems is necessary when interpreting older botanical terminology and current family descriptions. The sequence preserves the one-to-one correspondence between each older family name and its currently accepted equivalent.
419. A harmless pulse label marks only dividing cells near a root tip. Initially, labelled cells occur just above the root cap. Later, the same labelled cells are farther from the cap, first elongated and then associated with root hairs. Which interpretation best explains the observations?
ⓐ. Root hairs arise directly from dividing cells without an elongation stage.
ⓑ. The root cap produces cells that later form every root region.
ⓒ. Meristematic cells elongate and then mature into differentiated cells.
ⓓ. Mature root-hair cells repeatedly divide and move toward the root apex.
Correct Answer: Meristematic cells elongate and then mature into differentiated cells.
Explanation: The label first appears in cells undergoing division a few millimetres above the root cap, identifying the meristematic region. As the root apex continues growing, those labelled cells are displaced proximally relative to the cap. They next enlarge and elongate, indicating passage through the region of elongation. Farther from the apex, they differentiate, and some epidermal cells form root hairs in the region of maturation. The observations follow one cell population through successive developmental states rather than showing unrelated cells in separate zones. The root cap protects the apex but does not supply all root tissues. Root-hair cells are differentiated cells and are not the main source of new cells. The sequence demonstrates how cell division, elongation and maturation collectively produce root growth.
420. Roots with intact or experimentally removed root caps are grown through either soft gel or compact soil. In soft gel, both groups elongate similarly. In compact soil, capless roots show much greater apical injury and reduced penetration. The strongest inference is:
ⓐ. The root cap protects the apex while it penetrates resistant soil.
ⓑ. The root cap is the only region in which new root cells are produced.
ⓒ. The root cap directly forms all root hairs in compact soil.
ⓓ. The root cap controls whether the root system is tap or fibrous.
Correct Answer: The root cap protects the apex while it penetrates resistant soil.
Explanation: The two media separate ordinary elongation from the mechanical challenge of penetrating a resistant substrate. Similar growth in soft gel shows that removal of the cap does not immediately eliminate every process required for root elongation. The strong injury and poor penetration of capless roots in compact soil reveal the condition under which the cap is especially important. Its thimble-like position over the apex protects the delicate meristematic tissues from abrasion and mechanical damage as the root advances between soil particles. Cell production occurs mainly in the meristematic region behind the cap, while root hairs form much farther from the apex in the maturation region. Root-system category depends on developmental origin, such as radicle persistence or stem-base origin, and cannot be determined by the presence of the cap.
