501. Four reproductive experiments give the following results.
| Experiment | Observation |
|---|
| P | Self pollen lands on stigma but is rejected before sustained tube growth |
| Q | Compatible pollen reaches embryo sac; syngamy occurs but triple fusion is experimentally blocked |
| R | Double fertilisation occurs normally, but integuments fail to harden |
| S | No fertilisation occurs, but growth-substance treatment produces a seedless fruit |
Which experiment produces a normal zygote but fails to establish the normal primary endosperm lineage?
ⓐ. P
ⓑ. Q
ⓒ. R
ⓓ. S
Correct Answer: Q
Explanation: Experiment Q separates the two components of double fertilisation. Syngamy succeeds, so one male gamete fuses with the egg and establishes the diploid zygote. Triple fusion is specifically blocked, so the primary endosperm nucleus and subsequent normal endosperm lineage are not established. Experiment P fails earlier during pollen-pistil interaction and does not reach either fusion. Experiment R completes both fusions and instead has a later seed-coat defect. Experiment S bypasses fertilisation at the fruit-development level through parthenocarpy. Comparing the four experiments requires locating each failure within the reproductive sequence rather than merely recognising isolated terminology. Apomixis concerns embryo or seed formation without the normal fertilisation event, whereas parthenocarpy concerns fruit development without fertilisation. A single unusual reproductive outcome should not be overclassified: fertilisation status, embryo origin and embryo number each require their own evidence.
502. Which pair consists entirely of maternal sporophytic tissues, even though one may persist inside the seed and the other forms part of the fruit?
ⓐ. Egg and primary endosperm nucleus
ⓑ. Zygote and seed coat
ⓒ. Endosperm and embryo
ⓓ. Nucellus and pericarp
Correct Answer: Nucellus and pericarp
Explanation: Nucellus is diploid maternal tissue of the ovule that surrounds the female gametophyte. If part of it persists in the mature seed, it forms perisperm. Pericarp is also maternal sporophytic tissue, but it originates from the ovary wall during fruit development. Neither structure requires a paternal genetic contribution for its basic tissue identity. The egg is a haploid gametophytic cell, while zygote, embryo and primary endosperm nucleus are products of fertilisation-related events. Seed coat is maternal, but the pair containing it also includes a zygote and does not satisfy the condition. The distinction is developmental lineage rather than final position, since maternal tissues can contribute both internal seed components and external fruit structures.
503. In one normal embryo sac, how many haploid nuclear contributions are incorporated altogether into the two immediate nuclear products of double fertilisation?
ⓐ. \(5\)
ⓑ. \(4\)
ⓒ. \(6\)
ⓓ. \(7\)
Correct Answer: \(5\)
Explanation: Syngamy combines two haploid nuclear contributions: one from the egg and one from a male gamete. Triple fusion combines three more: two polar nuclear contributions and the second male gamete. Across the two fusion products, the total number of haploid nuclear contributions is:
\[
2+3=5
\]
These produce two different immediate products: a diploid zygote and a triploid primary endosperm nucleus. The count has biological meaning: it reconstructs the nuclear participation underlying double fertilisation rather than simply manipulating arbitrary numbers. It also explains why two male gametes are required even though the two resulting products have different ploidies and developmental fates. The total \(5\) is not the number of male gametes. Only two of the five haploid nuclear contributions are paternal male gametes; the other three are the egg and two polar nuclei from the female gametophyte. Counting contributions rather than gametes explains how two male gametes participate in two products whose combined nuclear inputs number five.
504. Which comparison correctly relates the future shoot region of a typical dicot embryo to that of a typical monocot embryo?
ⓐ. Both are enclosed by coleoptile, but only the dicot possesses a plumule
ⓑ. The dicot shoot arises from the radicle, while the monocot shoot arises from the scutellum
ⓒ. Both have embryonic shoots; the monocot shoot apex is protected by coleoptile
ⓓ. The monocot lacks a shoot apex because the scutellum replaces it
Correct Answer: Both have embryonic shoots; the monocot shoot apex is protected by coleoptile
Explanation: Both dicot and monocot embryos possess a future shoot system. In the typical dicot embryo, the epicotyl lies above the cotyledon level and terminates in the plumule. In the monocot embryo, the shoot apex and young leaf primordia are enclosed by a specialised protective sheath called the coleoptile. The presence of this sheath is a characteristic monocot feature and should not be transferred to the dicot embryo. The scutellum is the monocot cotyledon and does not replace the shoot apex. This comparison focuses on homologous developmental function while preserving the structural specialisation that distinguishes the two embryo types. A monocot embryo has one cotyledon called the scutellum, together with a coleoptile around the shoot region and a coleorrhiza around the root region.
505. One opening of the ovule has two different reproductive roles at different stages: it first provides a normal entry route for the pollen tube and later persists in the mature seed as a pore facilitating water and oxygen entry. This developmental continuity involves the:
ⓐ. persistent micropylar pore
ⓑ. persistent funicular hilum
ⓒ. persistent chalazal region
ⓓ. persistent funicular stalk
Correct Answer: persistent micropylar pore
Explanation: The micropyle is the opening left by the integuments at one end of the ovule. Before fertilisation, the pollen tube normally enters the ovule through this micropylar region and is guided toward a synergid. After the ovule develops into a seed, the micropyle does not simply disappear; it can persist as a small pore in the mature seed coat and facilitate entry of water and oxygen during germination. The same structure connects a pre-fertilisation transport function with a later seed-germination function. Hilum and funicle are related to ovule attachment, while the chalaza marks the opposite end of the ovule. The relation is developmental rather than a mere naming exercise. The persistent micropyle can remain as a small pore in the seed coat and may later facilitate entry of water or gases during germination.
506. A fruit has a normal pericarp and disperses normally, but the seed coats of its seeds are abnormally fragile because the integuments developed poorly. Which conclusion is most appropriate?
ⓐ. Both fruit dispersal and individual seed protection must fail completely
ⓑ. The embryo becomes triploid because its coat is weak
ⓒ. Fruit dispersal can remain normal while direct seed protection is reduced
ⓓ. Normal pericarp proves that seed coats must also be normal because both come from the ovary wall
Correct Answer: Fruit dispersal can remain normal while direct seed protection is reduced
Explanation: Pericarp and seed coat are protective structures at different organisational levels and arise from different maternal tissues. The pericarp develops from the ovary wall and can contribute to protection and dispersal of the enclosed seeds. Seed coats develop from the integuments of individual ovules and directly protect each seed. In the scenario, pericarp development and fruit dispersal remain normal, whereas defective integuments weaken the seed coverings. The two functions can be separated experimentally. A fragile seed coat does not alter embryo ploidy, and normal pericarp cannot guarantee normal seed coats: the two tissues do not share the same immediate developmental precursor. The pericarp and seed coat are both usually diploid maternal tissues, but one comes from the ovary wall and the other from the ovular integuments. The contrast localises the defect to integument-derived seed covering rather than to the independently derived ovary-wall pericarp.
507. Self pollen is deposited on a self-incompatible plant and is rejected before fertilisation. Nevertheless, viable seeds later form, and embryo development is shown to have occurred without fusion of a male gamete with the egg. What is the strongest inference?
ⓐ. Self-incompatibility failed because seed formation always proves fertilisation
ⓑ. The rejected pollen must have completed syngamy invisibly
ⓒ. The seeds are parthenocarpic because no fertilisation occurred
ⓓ. Apomixis bypassed the fertilisation blocked by self-incompatibility
Correct Answer: Apomixis bypassed the fertilisation blocked by self-incompatibility
Explanation: The self-incompatibility system has successfully prevented the ordinary sexual pathway as self pollen is rejected before fertilisation. The later appearance of viable seeds would ordinarily suggest reproductive success, but the decisive evidence is that embryo development occurred without male-gamete fusion. This identifies apomixis rather than failure of the incompatibility mechanism. The case demonstrates why seed production alone is not absolute proof that syngamy occurred when a plant has access to a fertilisation-independent seed pathway. Parthenocarpy concerns fruit formation without fertilisation and cannot account for the formation of viable seeds and embryos described here. The observation integrates a pre-fertilisation barrier with a post-pollination reproductive exception. Seed formation without fertilisation is evidence for apomixis, while fruit formation without fertilisation and without normal seeds points instead toward parthenocarpy.
508. Female plants of a dioecious species are completely isolated from male plants and pollinating agents. Their ovaries are then treated with a growth substance, and normal-sized seedless fruits develop. Which interpretation best fits the result?
ⓐ. Dioecy blocks selfing; induced parthenocarpy allows fruit without fertilisation
ⓑ. The treatment converts the isolated dioecious female flowers into functional bisexual flowers
ⓒ. Seedless fruit proves that xenogamy occurred before isolation
ⓓ. Parthenocarpy has produced apomictic seeds inside the fruits
Correct Answer: Dioecy blocks selfing; induced parthenocarpy allows fruit without fertilisation
Explanation: In a dioecious species, male and female flowers occur on different individual plants, so a female plant cannot perform autogamy or geitonogamy. Isolation from male plants and pollinating agents removes the normal opportunity for xenogamous fertilisation. The growth-substance treatment nevertheless stimulates ovary development into fruit, demonstrating induced parthenocarpy. The absence of normal seeds is consistent with fertilisation not occurring. The treatment does not change the sexual organisation of the flowers and does not create apomictic seeds. The case shows that an outbreeding arrangement governing pollen source and a fertilisation-independent fruit-development pathway can operate as separate biological features in the same plant. Seed formation without fertilisation is evidence for apomixis, while fruit formation without fertilisation and without normal seeds points instead toward parthenocarpy. Embryo number, embryo origin and fruit-development mechanism are three separate dimensions and should not be inferred from one another without supporting evidence.
509. Cleistogamous flowers normally produce seeds reliably. In an experiment, syngamy is completely blocked but pollen transfer within the closed flowers remains normal. Surprisingly, viable seeds still form. Which conclusion is most justified?
ⓐ. Cleistogamy alone cannot explain it; apomixis must be operating
ⓑ. Cleistogamy itself must produce seeds without fertilisation
ⓒ. Normal autogamy can produce a zygote even when syngamy is blocked
ⓓ. Closed flowers necessarily perform triple fusion without male gametes
Correct Answer: Cleistogamy alone cannot explain it; apomixis must be operating
Explanation: Cleistogamy assures self-pollen transfer: the flower remains closed, but ordinary seed formation in a cleistogamous flower can still depend on normal fertilisation. Blocking syngamy removes the normal route by which the egg becomes a zygote. If viable seeds nevertheless form, floral closure and autogamy are insufficient explanations as they govern pollen transfer rather than fertilisation-independent embryogenesis. The additional evidence points to apomixis, in which seed formation can occur without fertilisation. The experiment separates two concepts that may superficially appear similar since both can ensure seed set without external pollinators. Cleistogamy assures pollen delivery, whereas apomixis bypasses gametic fusion. Apomixis concerns embryo or seed formation without the normal fertilisation event, whereas parthenocarpy concerns fruit development without fertilisation. Cleistogamous flowers remain closed and therefore provide an especially reliable route for autogamy and assured seed set when the sexual structures are functional.
510. All pollen produced by a plant has lost viability before reaching the stigma. No pollen tubes form, yet treatment of the ovaries with a suitable growth substance produces mature seedless fruits. Which conclusion is best supported?
ⓐ. Non-viable pollen can still complete double fertilisation
ⓑ. Fruit set here does not prove successful pollination or fertilisation
ⓒ. The fruits must contain nucellar embryos because pollen tubes are absent
ⓓ. Loss of pollen viability automatically induces apomixis
Correct Answer: Fruit set here does not prove successful pollination or fertilisation
Explanation: Non-viable pollen cannot successfully germinate and complete the pollen-tube pathway needed for normal male-gamete delivery. The experiment explicitly confirms that no pollen tubes form, so ordinary fertilisation cannot account for the fruits. Growth-substance treatment has instead stimulated parthenocarpic development of the ovary. The resulting seedless fruits show that fruit formation can be experimentally uncoupled from pollination and fertilisation. No evidence indicates nucellar embryony or apomixis as no viable seeds or embryos are described. The case cautions against using fruit set alone as proof that the preceding sexual reproductive sequence was completed. Parthenocarpic fruit development and apomictic embryo formation describe different organs, so the two phenomena can occur independently or coexist under suitable conditions.
511. Which sequence correctly represents the normal sexual route before indicating where the two major fertilisation-independent exceptions branch away?
ⓐ. Pollination → fruit → gametophytes → double fertilisation → seed; apomixis → fruit converted into seed; parthenocarpy → fruit only after syngamy
ⓑ. Gametophytes → pollination → pollen tube → double fertilisation → seed and fruit; apomixis bypasses fertilisation for seed, parthenocarpy for fruit
ⓒ. Double fertilisation → pollen recognition → meiosis → fruit and seed; apomixis → seed only after pollen-tube growth; parthenocarpy → zygote formation
ⓓ. Gametophytes → seed maturation → pollination → syngamy → fruit; apomixis → seed after triple fusion; parthenocarpy → fruit after triple fusion
Correct Answer: Gametophytes → pollination → pollen tube → double fertilisation → seed and fruit; apomixis bypasses fertilisation for seed, parthenocarpy for fruit
Explanation: The normal sexual pathway first establishes male and female gametophytes. Pollination then transfers pollen to the stigma, but compatibility and successful pollen-tube growth are still required before male gametes reach the embryo sac. Double fertilisation follows and initiates the normal embryo and endosperm lineages, after which ovules and ovary proceed toward seed and fruit maturation. Apomixis and parthenocarpy create different departures from this sequence. Apomixis permits seed or embryo formation without fertilisation, while parthenocarpy permits fruit development without fertilisation. The correct sequence preserves both normal developmental dependency and the distinct points at which exceptional routes bypass the ordinary sexual requirement. The main route is constrained by successive gates: gametophytes must exist before pollination, compatible pollen-tube growth must precede double fertilisation, and fertilisation establishes the normal embryo and endosperm lineages before seed maturation. The exceptional routes branch by bypassing specific later gates rather than reversing this order.
512. Four reproductive routes are subjected to complete failure of pollen-tube delivery.
| Route | Special reproductive capacity |
|---|
| P | Normal sexual seed formation only |
| Q | Parthenocarpic fruit development |
| R | Diploid-egg apomictic embryo development |
| S | Normal zygotic embryogenesis only |
Which routes can still produce the stated reproductive product without restoration of pollen-tube delivery?
ⓐ. P and S only
ⓑ. P and Q only
ⓒ. Q and R only
ⓓ. R and S only
Correct Answer: Q and R only
Explanation: Complete pollen-tube failure prevents normal delivery of male gametes, so syngamy and triple fusion cannot proceed through the ordinary sexual pathway. Routes P and S cannot produce their normal sexual seed or zygotic embryo without restoration of male-gamete delivery. Route Q is independent of fertilisation at the fruit level: parthenocarpy allows ovary development without gametic fusion. Route R is also independent of pollen delivery as an unreduced diploid egg can develop apomictically without syngamy. The comparison shows that a single early failure can have different consequences depending on whether a plant possesses an alternative reproductive route that bypasses fertilisation. Parthenocarpic fruit development and apomictic embryo formation describe different organs, so the two phenomena can occur independently or coexist under suitable conditions. Apomixis concerns embryo or seed formation without the normal fertilisation event, whereas parthenocarpy concerns fruit development without fertilisation.
513. Consider the following statements.
I. Pollination places pollen on a stigma but does not by itself establish a zygote.
II. Syngamy is required for formation of the normal sexual zygote.
III. Triple fusion establishes the normal primary endosperm nucleus.
IV. Failure of fertilisation always prevents both seed and fruit formation in every flowering plant.
ⓐ. The true statements are I and IV only
ⓑ. The true statements are II and IV only
ⓒ. The true statements are I, II, III and IV
ⓓ. The true statements are I, II and III only
Correct Answer: The true statements are I, II and III only
Explanation: Pollination is a transfer event and must be followed by successful pollen-pistil interaction, pollen-tube growth and male-gamete delivery before fertilisation can occur. Syngamy then produces the normal diploid zygote, while triple fusion produces the primary endosperm nucleus. Statements I, II and III preserve the correct sequence and roles of these events. Statement IV is too absolute as exceptional reproductive pathways exist. Apomixis can permit seed formation without fertilisation, while parthenocarpy can permit fruit development without fertilisation. The statement set tests both the normal sexual route and the limits of treating that route as universal. The statements trace successive reproductive gates: pollen arrival, zygote formation and fertilisation-independent alternatives must be distinguished from one another. Changes in pollen transport can alter deposition without changing pollen ploidy, embryo-sac organisation or the later fusion products of double fertilisation.
514. Four mutations act at different points of the reproductive sequence.
P. Tapetal failure causes developing pollen to collapse.
Q. The pistil rejects deposited pollen before sustained tube growth.
R. Triple fusion is blocked but syngamy succeeds.
S. Ovular integuments fail to form a normal seed coat after double fertilisation.
Which mutation acts latest in the normal reproductive sequence?
ⓐ. S
ⓑ. P
ⓒ. Q
ⓓ. R
Correct Answer: S
Explanation: Tapetal failure acts during pollen development, well before pollination. Pollen rejection by the pistil occurs after pollen deposition but before male-gamete delivery. Blocking triple fusion acts later still, during double fertilisation inside the embryo sac. Failure of integuments to form a normal seed coat occurs after fertilisation during seed maturation. Mutation S acts latest among the four. The comparison requires ordering mechanisms from male-gametophyte development through pollen-pistil interaction and fertilisation to post-fertilisation transformation. Similar final reproductive failure does not imply that mutations act at the same stage; identifying the earliest affected biological process is essential for locating each defect in the full reproductive pathway. The tapetum is the innermost microsporangial wall layer and supports developing microspores, whereas the sporogenous lineage gives rise to pollen mother cells. Successful male function therefore depends on both production of viable pollen and its effective presentation for transfer from the anther.
515. A male parent carries a diagnostic genetic marker absent from the female parent. After normal fertilisation, four mature tissues are tested.
| Tissue | Paternal marker detected? |
|---|
| P. Embryo | Yes |
| Q. Endosperm | Yes |
| R. Seed coat | No |
| S. Pericarp | No |
Which interpretation best explains this pattern?
ⓐ. Only the seed coat and pericarp are products of double fertilisation
ⓑ. Embryo and endosperm have paternal input; seed coat and pericarp are maternal
ⓒ. Paternal genes enter all four tissues but become inactive in R and S
ⓓ. Endosperm and pericarp are paternal tissues, whereas embryo and seed coat are maternal
Correct Answer: Embryo and endosperm have paternal input; seed coat and pericarp are maternal
Explanation: The embryo arises from the zygote formed when a male gamete fuses with the egg, so paternal nuclear material enters the embryonic lineage. Endosperm begins from the central-cell fertilisation product formed when the second male gamete participates in triple fusion, so it can also contain the paternal marker. Seed coat and pericarp have different origins. Seed coats develop from the maternal ovular integuments, whereas the pericarp develops from the maternal ovary wall. Their failure to show the paternal marker is expected even in a fruit produced after completely normal fertilisation. The experiment distinguishes fertilisation-derived tissues from maternal sporophytic tissues by lineage rather than by location within the mature fruit. Maternal seed coverings and fertilisation-derived internal tissues can coexist in a mature seed, so location alone does not reveal developmental origin. The pericarp and seed coat are both usually diploid maternal tissues, but one comes from the ovary wall and the other from the ovular integuments. The marker pattern therefore separates fertilisation-derived internal lineages from maternal coverings even though all four tissues occur in the same mature reproductive structure.
516. A mutation prevents meiosis in both pollen mother cells and megaspore mother cells but leaves surrounding anther and ovule tissues structurally normal. Which reproductive consequence is most directly expected?
ⓐ. Both mother-cell types produce normal haploid spores by mitosis
ⓑ. Only the female lineage is affected because microspores do not require meiosis
ⓒ. Diploid sporophytic tissues become haploid throughout the flower
ⓓ. Both lineages fail to form normal haploid microspores or megaspores
Correct Answer: Both lineages fail to form normal haploid microspores or megaspores
Explanation: Pollen mother cells and megaspore mother cells are both diploid sporophytic cells whose normal function is to undergo meiosis. In the male lineage, this reduction division produces haploid microspores; in the female lineage, it produces haploid megaspores. If meiosis is specifically prevented in both mother-cell types, the normal \(2n\rightarrow n\) transition cannot occur in either lineage. Surrounding anther and ovule tissues can remain diploid and structurally recognisable as the mutation is restricted to the meiotic step. The result demonstrates a shared developmental requirement of male and female sporogenesis: both depend on reduction division before their respective haploid gametophytes can develop normally. A pollen mother cell is diploid, but its meiotic products are haploid microspores; later pollen cells belong to the haploid male gametophyte. The megaspore mother cell is a diploid nucellar cell, whereas the megaspores produced by its meiosis are haploid and belong to the female gametophytic lineage.
517. A normal \(7\)-celled, \(8\)-nucleate embryo sac has completed cellular organisation. Before the pollen tube arrives, its two haploid polar nuclei fuse to form one secondary nucleus, and no other nucleus divides or degenerates. What is the immediate condition?
ⓐ. \(8\) cells, \(8\) nuclei; central secondary nucleus \(n\)
ⓑ. \(7\) cells, \(7\) nuclei; central secondary nucleus \(2n\)
ⓒ. \(7\) cells, \(8\) nuclei; central secondary nucleus \(3n\)
ⓓ. \(6\) cells, \(7\) nuclei; central zygote \(2n\)
Correct Answer: \(7\) cells, \(7\) nuclei; central secondary nucleus \(2n\)
Explanation: Cellular organisation is already complete, so fusion of the two polar nuclei does not change the number of cells. The embryo sac remains \(7\)-celled. What changes is the number of distinct nuclear bodies. Two separate haploid polar nuclei become one diploid secondary nucleus:
\[
n+n=2n
\]
so the number of distinct nuclei decreases from \(8\) to \(7\). The egg, two synergid nuclei and three antipodal nuclei remain unchanged. This condition should not be confused with fertilisation since no male gamete has yet arrived. Later, fusion of an \(n\) male gamete with the \(2n\) secondary nucleus can establish the normal \(3n\) primary endosperm nucleus. The cell count remains \(7\) since fusion of the polar nuclei occurs within the already existing central cell and does not create or remove a cell. The distinct nuclear count falls from \(8\) to \(7\) when two \(n\) polar nuclei become one \(2n\) secondary nucleus. That difference between cell number and nuclear number is the key bookkeeping step.
518. An ovule has a normal embryo sac, integuments, micropyle and hilum, but its funicle is experimentally severed between the ovule and the placenta. Which structural relation is most directly disrupted?
ⓐ. The micropylar opening between the integuments
ⓑ. The position of the egg apparatus within the embryo sac
ⓒ. Funicular attachment of the ovule to the placenta
ⓓ. Formation of the chalazal end opposite the micropyle
Correct Answer: Funicular attachment of the ovule to the placenta
Explanation: The funicle is the stalk that physically attaches the ovule to the placenta inside the ovary. Severing that stalk disrupts the ovule-placenta connection directly. The hilum marks the region where the funicle joins the ovule body, but it is not itself the stalk extending to the placenta. The micropyle is an opening left by the integuments and remains a separate structural feature, while the chalaza defines the opposite basal region of the ovule. The position of the egg apparatus belongs to embryo-sac organisation and is not created by the funicle. The experiment distinguishes the attachment function of the funicle from the orientation and internal reproductive structures of the ovule. The funicle attaches the ovule to the placenta, and the hilum marks the point where that stalk joins the ovule body.
519. A two-celled pollen grain germinates normally on a compatible stigma and produces a pollen tube that grows through the style. A treatment specifically prevents mitosis of its generative cell but does not impair vegetative-cell function or tube growth. What is the most direct reproductive consequence?
ⓐ. The pollen tube becomes diploid and completes fertilisation normally
ⓑ. Triple fusion occurs first and subsequently produces two male gametes
ⓒ. Double fertilisation fails because two male gametes are not produced
ⓓ. The pollen grain is converted into a three-celled female gametophyte
Correct Answer: Double fertilisation fails because two male gametes are not produced
Explanation: Two-celled pollen contains a vegetative cell and an undivided generative cell. The vegetative cell can support pollen-tube growth, explaining why the tube still travels through the style. The generative cell, however, normally undergoes mitosis to form the two haploid male gametes required for double fertilisation. Blocking that mitosis prevents production of the normal pair of male gametes even though the delivery structure develops successfully. One male gamete is required for syngamy with the egg and the other for triple fusion with the polar nuclear system. The experiment separates pollen-tube formation from male-gamete production and shows that successful transport alone is insufficient for complete fertilisation. In two-celled pollen, the vegetative cell supports pollen-tube growth while the generative cell later divides mitotically to produce two male gametes. Three-celled pollen already contains the vegetative cell and two male gametes at shedding, whereas two-celled pollen completes generative-cell division later.
520. A monoecious wind-pollinated plant bears separate male and female flowers on the same individual, while neighbouring individuals of the same species are also present. Wind carries pollen from one male flower to receptive female flowers. Which statement is most accurate?
ⓐ. Wind transport makes every transfer xenogamous
ⓑ. Monoecy makes every wind-mediated transfer autogamous
ⓒ. Wind pollination prevents transfer between flowers of the same individual
ⓓ. Wind may cause geitonogamy within a plant or xenogamy between plants
Correct Answer: Wind may cause geitonogamy within a plant or xenogamy between plants
Explanation: Pollinating agent and pollen-transfer category answer different biological questions. Wind identifies the transport mechanism, whereas geitonogamy and xenogamy depend on the identities of the donor and recipient plants. In a monoecious individual, pollen moving from a male flower to a female flower on the same plant is geitonogamy. If wind carries that pollen to a female flower on another individual, the transfer is xenogamy. Autogamy is impossible within the separate unisexual flowers since one flower does not contain both functional male and female reproductive organs. The same abiotic agent can produce genetically different classes of pollen transfer depending on destination. Wind pollination is favoured by efficient pollen release, light non-sticky grains and receptive surfaces that can intercept airborne pollen.
