Sexual Reproduction in Flowering Plants ISC Class 12 Biology

What Sexual Reproduction in Flowering Plants is about

Weightage: Sexual Reproduction in Flowering Plants is part of the unit Reproduction, which carries 16 of the 70 marks in the ISC Biology Paper 1 (Theory), shared with 2 other chapters. Questions on it can appear in any section of the paper.Source: CISCE ISC Biology syllabus, examination year 2027, distribution of marks

Key concepts

Anther, microsporangium and microsporogenesis

A typical anther is bilobed and dithecous (two thecae per lobe), with four microsporangia (tetrasporangiate) at its corners. Development: a mass of meristematic cells; a hypodermal archesporial cell (archesporial initial) divides periclinally into an outer primary parietal layer and an inner primary sporogenous cell. The parietal layer gives the wall layers; the sporogenous cells give the microspore mother cells (pollen mother cells, 2n). Wall of microsporangium (outside in): epidermis (protective); endothecium (fibrous thickenings, helps dehiscence); middle layers (2-3, degenerate); tapetum (innermost, cells with dense cytoplasm and often more than one nucleus; nourishes developing pollen and secretes materials for the exine, e.g. sporopollenin precursors). Microsporogenesis: each microspore mother cell divides by meiosis to form a tetrad of four haploid microspores. As the anther dries, the microspores separate and develop into pollen grains. The anther dehisces along the stomium.

Worked example

An anther has 20 microspore mother cells in each of its microsporangia. How many pollen grains will it produce, and how many meiotic divisions are needed?

Try it first, then show the solutionSolution

1. 4 microsporangia × 20 = 80 microspore mother cells.
2. Each undergoes one meiosis giving 4 microspores: 80 meiotic divisions, 80 × 4 = 320 pollen grains.

Answer: 320 pollen grains; 80 meiotic divisions

Pollen grain: structure, development, viability and importance

Wall: two layers. Exine: hard, made of sporopollenin, one of the most resistant organic materials known (withstands high temperatures, strong acids and alkalis; no enzyme degrades it), so pollen is well preserved as fossils; it has germ pores where sporopollenin is absent. Intine: thin, continuous, of cellulose and pectin. Development (male gametophyte): the microspore nucleus divides by mitosis into a large vegetative cell (food reserve, irregular nucleus) and a small generative cell floating in its cytoplasm. In over 60% of angiosperms pollen is shed at this two-celled stage; in the rest the generative cell divides into two male gametes first (three-celled stage). Viability: the period pollen remains able to germinate: about 30 minutes in rice and wheat, several months in members of Rosaceae, Leguminosae and Solanaceae. Pollen can be stored for years in liquid nitrogen (−196 °C) in pollen banks for crop breeding. Economic importance: pollen tablets and syrups as food supplements (athletes, race horses); pollen of some plants (Parthenium, carrot grass) causes allergies, asthma and bronchitis; used to study vegetation history (palynology).

Worked example

Why are pollen grains well preserved as fossils, and why are they stored in liquid nitrogen in crop breeding?

Try it first, then show the solutionSolution

1. The exine contains sporopollenin, which resists heat, acids, alkalis and enzymes, so the grains do not decay.
2. At −196 °C metabolism stops, so pollen remains viable for years; breeders can use pollen of desired varieties when needed.

Answer: Sporopollenin; cryopreservation keeps viability

Pistil, ovule and the female gametophyte

The pistil has stigma (landing platform for pollen), style and ovary; ovules are attached to the placenta in the ovarian cavity. Anatropous ovule (L.S.): attached by a stalk, the funicle, at the hilum; the body is inverted so the micropyle lies near the funicle. One or two protective integuments enclose the nucellus, leaving the micropyle at the tip; the base opposite is the chalaza. The embryo sac lies in the nucellus. Megasporogenesis: a megaspore mother cell (2n) near the micropylar end divides by meiosis into a linear tetrad of four megaspores; usually three degenerate and one becomes the functional megaspore (monosporic development). Embryo sac formation (Polygonum type): the functional megaspore nucleus divides mitotically three times (free nuclear divisions) to give 8 nuclei, four at each pole; then cell walls form. Mature embryo sac: 7 cells, 8 nuclei. At the micropylar end, the egg apparatus: one egg cell and two synergids with special thickenings, the filiform apparatus, which guide the pollen tube into the synergid. At the chalazal end, three antipodal cells. In the centre, the large central cell with two polar nuclei (which may fuse to form a secondary nucleus).

Worked example

The megaspore mother cell of a plant has 16 chromosomes. How many chromosomes are in a synergid nucleus and in each polar nucleus, and how many in all the nuclei of the mature embryo sac together?

Try it first, then show the solutionSolution

1. Meiosis halves the number: the functional megaspore and every embryo-sac nucleus derived from it by mitosis has n = 8.
2. Synergid nucleus 8; each polar nucleus 8.
3. The 7-celled embryo sac has 8 nuclei: 8 × 8 = 64 chromosomes in all.

Answer: Synergid 8, each polar nucleus 8; 64 in total

Pollination: types, agents and adaptations

Autogamy: pollen to the stigma of the same flower. Needs synchrony of pollen release and stigma receptivity, and anthers and stigma close together. Chasmogamous flowers open, exposing anthers and stigma (may be self- or cross-pollinated); cleistogamous flowers never open (Viola, Oxalis, Commelina) and are invariably autogamous, giving assured seed set even without pollinators. Geitonogamy: pollen to another flower of the same plant; functionally (ecologically) cross-pollination because an agent carries pollen, but genetically self-pollination because the pollen comes from the same plant. Xenogamy: pollen to a flower of a different plant of the same species; brings genetically different pollen. Wind (anemophily): light, non-sticky pollen in large numbers, well-exposed stamens, large feathery stigma, often a single ovule per ovary, flowers in tassels (maize, grasses). Water (hydrophily): rare, about 30 genera, mostly monocots: Vallisneria (female flowers reach the surface on long stalks; male flowers released and carried on the water), Hydrilla, Zostera (sea grass, long ribbon-like pollen); pollen protected by a mucilage covering. Water lily and lotus are pollinated by insects or wind, not water. Insects (entomophily): large, colourful, fragrant flowers rich in nectar; sticky pollen; some offer floral rewards or safe places to lay eggs (yucca and moth; Amorphophallus). Also birds and bats. Advantages: self-pollination preserves parental characters and is sure; cross-pollination brings variation, vigour and adaptability.

Worked example

A plant has small flowers with exposed stamens, a large feathery stigma and light pollen produced in huge numbers. Identify the pollinating agent and give one reason for each feature.

Try it first, then show the solutionSolution

1. Wind pollination (anemophily).
2. Exposed stamens release pollen into the air; a feathery stigma traps airborne grains; large numbers compensate for the wastage of random dispersal; light pollen stays airborne.

Answer: Wind

Outbreeding devices, pollen-pistil interaction and artificial hybridisation

Continued self-pollination causes inbreeding depression, so plants have contrivances to prevent self-pollination: (1) dichogamy: pollen release and stigma receptivity are not synchronised: protandry (anthers mature first: sunflower) or protogyny (stigma first: Mirabilis); (2) herkogamy: anther and stigma at different positions, so pollen cannot reach the stigma of the same flower (e.g. heterostyly); (3) self-incompatibility: a genetic mechanism that stops pollen of the same flower (or plant) from germinating on the stigma or growing in the style; (4) unisexual flowers: monoecious plants (castor, maize: prevents autogamy, not geitonogamy) and dioecious plants (papaya, date palm: prevent both). Pollen-pistil interaction: the pistil recognises compatible pollen of the right species by chemical signals between the pollen and the stigma and style; compatible pollen germinates, the pollen tube grows through the stigma and style, enters the ovule through the micropyle and then enters a synergid, guided by the filiform apparatus; incompatible pollen is rejected. Artificial hybridisation (crop improvement): only desired pollen is used. Emasculation: remove anthers from a bisexual flower bud before they dehisce. Bagging: cover the emasculated flower with butter paper to prevent contamination. When the stigma is receptive, dust pollen from the selected male parent and re-bag. Unisexual female flowers need bagging only. Significance: combines desirable characters of two parents into a new variety.

Worked example

Wind carries pollen from a wheat field onto the stigmas of other wheat plants and of a nearby mustard crop. Which pollen can lead to seed formation, and why?

Try it first, then show the solutionSolution

1. Pollen-pistil interaction is species-specific: the pistil recognises compatible pollen through chemical signals between pollen and stigma or style.
2. Wheat pollen on wheat stigmas is compatible: it germinates and its tube reaches the ovule.
3. Wheat pollen on mustard stigmas is from a different species and is rejected, so no fertilisation or seed results.

Answer: Only wheat pollen on wheat stigmas; mustard pistils reject the foreign pollen

Double fertilisation and triple fusion

Events leading to fertilisation: pollen lands on the stigma, germinates through a germ pore, and the pollen tube grows down the style; if pollen was shed two-celled, the generative cell divides in the tube to form two male gametes. The tube enters the ovule through the micropyle (porogamy) and penetrates a synergid through the filiform apparatus, releasing both male gametes. Syngamy: one male gamete fuses with the egg → diploid zygote (2n). Triple fusion: the other male gamete fuses with the two polar nuclei (or the secondary nucleus) in the central cell → triploid primary endosperm nucleus (PEN, 3n); the central cell becomes the primary endosperm cell. Because two fusions occur in one embryo sac, it is called double fertilisation, a feature unique to angiosperms. Significance: the triploid endosperm forms only when fertilisation occurs, so the plant does not waste food on unfertilised ovules; the endosperm nourishes the developing embryo; combining two maternal and one paternal set adds vigour.

Worked example

A diploid (2n) plant is used as the female parent and a tetraploid (4n) plant of a compatible species as the male parent. What is the ploidy of the zygote and of the endosperm?

Try it first, then show the solutionSolution

1. Egg and each polar nucleus of the 2n female are n; male gametes of the 4n male are 2n.
2. Zygote = n + 2n = 3n.
3. Endosperm = n + n + 2n = 4n.

Answer: Zygote 3n; endosperm 4n

Endosperm, embryo, seed and fruit

Endosperm develops before the embryo. Nuclear type (most common, e.g. in polypetalous dicots): PEN divides repeatedly without wall formation (free nuclei); walls form later from the periphery. The coconut's water is free-nuclear endosperm and the white kernel cellular endosperm. Cellular type: every division followed by wall formation. Helobial type (monocots): the first division forms a large micropylar and small chalazal chamber; the micropylar chamber is free-nuclear, the chalazal one cellular. Embryo: the zygote divides at the micropylar end. Dicot embryo (bean): an embryonal axis with two cotyledons; above the cotyledons the epicotyl ends in the plumule; below, the hypocotyl ends in the radicle covered by the root cap. Monocot embryo (maize): one large shield-shaped cotyledon, the scutellum; the plumule is enclosed by the coleoptile and the radicle by the coleorhiza. Seed: the fertilised ovule; integuments form the seed coat (testa and tegmen), micropyle remains as a pore, hilum as a scar. Albuminous (endospermic) seeds keep endosperm (wheat, maize, castor, barley); non-albuminous (exalbuminous) seeds use it up during development and store food in cotyledons (pea, groundnut, bean). Perisperm: remnant nucellus persisting in the seed (black pepper, beet). Seeds become dry (10-15% moisture) and may enter dormancy. Fruit: the ovary wall becomes the pericarp (epicarp, mesocarp, endocarp). True fruit: develops only from the ovary (mango). False fruit: other floral parts such as the thalamus also form the fruit (apple, strawberry, cashew). Mango (L.S.): thin epicarp, fleshy edible mesocarp, hard stony endocarp, seed inside (a drupe). Coconut: smooth epicarp, fibrous mesocarp (coir), hard endocarp (shell), seed with liquid and cellular endosperm. Significance: seeds protect and disperse the embryo, store food, allow dormancy and perennation, bring variation through sexual reproduction; fruits protect seeds and help dispersal. Dispersal avoids crowding and competition with the parent and helps colonise new areas.

Worked example

In one type of endosperm development the first division of the primary endosperm nucleus forms a large micropylar chamber and a small chalazal chamber. Name the type and say where it is common.

Try it first, then show the solutionSolution

1. This is helobial endosperm, intermediate between nuclear and cellular types.
2. The micropylar chamber then undergoes free-nuclear divisions and the chalazal chamber is cellular (or stays undivided); it is common in monocots.

Answer: Helobial endosperm; common in monocots

Apomixis, polyembryony and parthenocarpy

Apomixis: production of seeds without fertilisation, a form of asexual reproduction that mimics sexual reproduction (Asteraceae, grasses). Ways: a diploid egg forms without reduction division and develops into an embryo; or nucellus or integument cells divide and protrude into the embryo sac to form embryos. Importance: hybrid seeds lose their vigour if farmers sow the next generation (characters segregate); if hybrids could be made apomictic, farmers could reuse hybrid seed every year. Polyembryony: occurrence of more than one embryo in a seed, e.g. citrus (orange) and mango, where nucellar cells form extra embryos alongside the zygotic one. Parthenocarpy: development of fruit without fertilisation; the fruits are seedless (banana); can be induced by growth hormones (auxins, gibberellins) as in seedless grapes and tomatoes. Differences between apomixis and polyembryony: apomixis is seed formation without fertilisation (embryo genetically identical to the parent); polyembryony is the presence of several embryos in one seed, which may arise from zygote and nucellus together.

Worked example

Three seedlings grow from one citrus seed. Two look exactly like the mother tree, but one differs. Explain.

Try it first, then show the solutionSolution

1. Citrus shows polyembryony: one seed contains several embryos.
2. Embryos formed from nucellar cells (adventive embryony, a form of apomixis) are genetically identical to the mother, so two seedlings are clones.
3. The third came from the zygote formed by fertilisation, so it carries genes from both parents and differs.

Answer: Polyembryony: two nucellar (clonal) embryos and one zygotic embryo

Sexual Reproduction in Flowering Plants in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Topics in this chapter

• Pollination and Outbreeding Devices
• Double Fertilisation and Post-fertilisation Events
• Microsporogenesis and Pollen Grain

Sexual Reproduction in Flowering Plants: key facts

Pollen count per anther

$\text{pollen grains}=4\times \text{(number of microspore mother cells)}$

One meiosis per mother cell gives a tetrad.

Meiotic divisions for seeds

$\text{meioses for }x\text{ seeds}=x\text{(megaspore mother cells)}+\frac{x}{4}\text{(microspore mother cells)}$

100 seeds need 125 meiotic divisions.

Embryo sac

$1\text{functional megaspore}\stackrel{3\text{mitoses}}{\to }8\text{nuclei},7\text{cells}$

Egg apparatus 3, antipodals 3, central cell 1 (2 polar nuclei).

Double fertilisation

$\text{egg (n)}+\text{male gamete (n)}\to \text{zygote (2n)};2\text{polar nuclei (n + n)}+\text{male gamete (n)}\to \text{PEN (3n)}$

Syngamy + triple fusion.

Ploidy of seed parts (diploid plant)

$\text{embryo}=2n,\text{endosperm}=3n,\text{perisperm, seed coat, pericarp}=2n$

Nucellus and integuments are maternal tissue.

Fruit wall

$\text{ovary wall}\to \text{pericarp}=\text{epicarp}+\text{mesocarp}+\text{endocarp}$

Ovule → seed; integuments → seed coat.

Sexual Reproduction in Flowering Plants: diagrams to practise

Practise each one on paper: draw it from the checklist, then tick off every label.

How the board asks Sexual Reproduction in Flowering Plants

The question patterns to expect, and the method that works for each.

Tricks to remember Sexual Reproduction in Flowering Plants

Short memory aids. Say each one aloud once, then use it on a question the same day.

• Every Excellent Man Thinks

  Anther wall outside in: Epidermis, Endothecium, Middle layers, Tapetum.

  Use it when: T.S. of anther labels.

• 3-2-3 embryo sac

  3 at micropyle (egg + 2 synergids), 2 polar nuclei in the middle, 3 antipodals at chalaza.

  Use it when: Embryo sac structure and counts.

• Auto-Geito-Xeno: flower, plant, other plant

  Same flower, same plant, different plant.

  Use it when: Types of pollination.

• Apples are false

  False fruits use the thalamus: apple, strawberry, cashew; mango is true.

  Use it when: True vs false fruits.

• Coconut: water nuclear, kernel cellular

  Drink the free nuclei, eat the cells.

  Use it when: Endosperm questions.

Sexual Reproduction in Flowering Plants: board-level solved questions

Ordered from board level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section D style)

Read the situation, then answer every part. In the board paper this is a 5-mark question split into 1 + 1 + 1 + 2 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Sexual Reproduction in Flowering Plants

The slips examiners see most often, and what to write instead.

• ✗Mistake: Wrong names and spellings for cells and endosperm types

  CISCE examiners' comments, 2024: for the hypodermal cell of a young anther candidates wrote 'archegonial initial' or named Leydig cells, tapetum or megaspore mother cell; they misspelt helobial and nuclear ('hellobial', 'nucellar') and gave 'cellular' instead of nuclear endosperm for polypetalous dicots.

  Wrong working

  archegonial initial; hellobial; nucellar endosperm

  Right working

  archesporial initial; helobial; nuclear endosperm

  ✓Do this: Practise spelling key terms; nucellar refers to the nucellus, not endosperm.

  Usually costs: 1 mark each.

• ✗Mistake: Drawing the wrong section

  CISCE examiners' comments, 2024: asked for T.S. of anther, candidates drew L.S. of anther, or even a testis with seminiferous tubules and Leydig cells.

  Wrong working

  An elongated anther with pollen sacs along its length.

  Right working

  A four-lobed transverse view with wall layers, pollen grains and connective.

  ✓Do this: T.S. = cut across: round outline with four sporangia.

  Usually costs: 2-3 marks.

• ✗Mistake: Common words instead of botanical terms

  CISCE examiners' comments, 2024 and 2025: candidates labelled fruit layers as skin, flesh and hard cover instead of epicarp, mesocarp, endocarp; confused true and false fruits with seeds or fertilisation; described fruit formation when its significance was asked; and gave vague answers (endocarp, kernel, liquid part) for coconut water instead of endosperm.

  Wrong working

  Coconut water comes from the white kernel.

  Right working

  Coconut water is the free-nuclear endosperm.

  ✓Do this: Use the syllabus term every time.

  Usually costs: 1 mark each.

• ✗Mistake: Misreading the question on nuclei and ploidy

  CISCE examiners' comments, 2025: for nuclei in the central cell, candidates wrote 8 (the whole embryo sac) or one; for a tetraploid female pollinated by a diploid male, they repeated 'triploid endosperm' without analysing the parents' ploidy.

  Wrong working

  Endosperm is always 3n.

  Right working

  Endosperm = 2 polar nuclei (2n each from a 4n plant) + male gamete (n) = 5n.

  ✓Do this: Work out the ploidy of each gamete before adding.

  Usually costs: 1 mark.

• ✗Mistake: Confusing outbreeding devices with hybridisation and mixing up apomixis

  CISCE examiners' comments, 2024 and 2025: for contrivances against self-pollination, candidates wrote emasculation and bagging; they said rose × China rose would work, missing incompatibility between species; they gave a vague location for the filiform apparatus; and they defined parthenocarpy instead of polyembryony or described apomixis as fruits formed without fertilisation.

  Wrong working

  Apomixis: fruit formation without fertilisation.

  Right working

  Apomixis: seed formation without fertilisation. Parthenocarpy: fruit without fertilisation. Polyembryony: more than one embryo in a seed.

  ✓Do this: Learn the three definitions side by side.

  Usually costs: 1-2 marks.

Practice questions on Sexual Reproduction in Flowering Plants

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQBoard level

   The innermost wall layer of the microsporangium which nourishes developing pollen is:
   (a) endothecium
   (b) epidermis
   (c) tapetum
   (d) middle layer

   Hint

   Nutritive layer.

   Answer

   (c) tapetum

2. Q2 · 1 mark · MCQBoard level

   Which is a false fruit?
   (a) mango
   (b) apple
   (c) coconut
   (d) tomato

   Hint

   Thalamus.

   Answer

   (b) apple

3. Q3 · 1 mark · Assertion-reasonBoard level

   Assertion: Pollen grains are well preserved as fossils.
   Reason: The exine is made of sporopollenin, which is resistant to strong acids, alkalis and enzymes.
   (a) Both true, Reason explains Assertion
   (b) Both true, Reason does not explain
   (c) Assertion true, Reason false
   (d) Both false

   Hint

   Exine.

   Answer

   (a)

4. Q4 · 1 mark · Very short answerBoard level

   Name the structure that remains as a small pore in the seed coat.

   Hint

   Pollen tube entry.

   Answer

   Micropyle

5. Q5 · 2 marks · Short answerHarder board level

   In an angiosperm with 2n = 24, give the chromosome number in (a) the antipodal cell, (b) the endosperm, (c) the nucellus.

   Hint

   Gametophyte cells are n.

   Answer

   (a) 12 (n) (b) 36 (3n) (c) 24 (2n)

6. Q6 · 2 marks · Short answerBoard level

   List four adaptations of wind-pollinated flowers.

   Hint

   Maize.

   Answer

   Light, non-sticky pollen in large numbers; well-exposed stamens; large feathery stigma; small, inconspicuous flowers often in tassels; single ovule per ovary.

7. Q7 · 2 marks · Short answerHarder board level

   How many meiotic divisions are needed to form 60 seeds?

   Hint

   Seeds + seeds/4.

   Answer

   60 (megaspore mother cells) + 15 (microspore mother cells) = 75.

8. Q8 · 3 marks · Short answerHarder board level

   Describe the structure of a pollen grain and the two-celled and three-celled stages of shedding.

   Hint

   Exine, intine, vegetative and generative cells.

   Answer

   Wall: hard exine of sporopollenin with germ pores, and thin intine of cellulose and pectin. Inside: a large vegetative cell with food and irregular nucleus, and a small spindle-shaped generative cell. Most angiosperms shed pollen at this 2-celled stage; in others the generative cell divides mitotically into two male gametes before shedding (3-celled stage).

9. Q9 · 3 marks · Short answerHarder board level

   Compare the embryos of a dicot (bean) and a monocot (maize) seed in three ways.

   Hint

   Cotyledons, sheaths.

   Answer

   Dicot: two cotyledons; no coleoptile or coleorhiza; often non-albuminous. Monocot: one cotyledon (scutellum); plumule enclosed in coleoptile and radicle in coleorhiza; albuminous with large endosperm and aleurone layer.

10. Q10 · 2 marks · Short answerHOTS / competency

    Why does a dioecious plant prevent both autogamy and geitonogamy, while a monoecious plant prevents only autogamy?

    Hint

    Where are the male flowers?

    Answer

    In a monoecious plant (castor, maize) male and female flowers are on the same plant, so pollen can still reach another flower of the same plant (geitonogamy). In a dioecious plant (papaya) each plant bears only one sex, so pollen must come from another plant.

11. Q11 · 5 marks · Long answerHarder board level

    (a) Describe megasporogenesis and development of the embryo sac. [3]
    (b) What is meant by monosporic development? [1]
    (c) Give the ploidy of the egg, synergid and PEN. [1]

    Hint

    Polygonum type.

    Answer

    (a) A megaspore mother cell in the nucellus near the micropyle divides by meiosis into a linear tetrad; three megaspores degenerate; the functional one undergoes three free-nuclear mitoses to form 8 nuclei (4 at each pole); one nucleus from each pole moves to the centre as polar nuclei; walls form, giving a 7-celled, 8-nucleate embryo sac. (b) The embryo sac develops from a single megaspore. (c) Egg n, synergid n, PEN 3n.

12. Q12 · 2 marks · Short answerHOTS / competency

    A farmer finds that his banana plants produce fruit without seeds and that orange seeds give several seedlings. Name and explain both phenomena.

    Hint

    Fruit vs embryos.

    Answer

    Banana: parthenocarpy, fruit development without fertilisation, so no seeds. Orange: polyembryony, several embryos (nucellar and zygotic) in one seed, each giving a seedling.

13. Q13 · 2 marks · Short answerHOTS / competency

    A flower has anthers that mature before its stigma becomes receptive. Name this device and its effect. Would self-incompatibility make it unnecessary?

    Hint

    Protandry.

    Answer

    Protandry (a form of dichogamy), which prevents autogamy by timing. Self-incompatibility independently stops self-pollen from fertilising; either device alone prevents selfing, but together they make outcrossing more certain (protandry also reduces wastage of pollen on its own stigma).

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.What is sporopollenin?Show answer

   The highly resistant material of the pollen exine.

2. 2.Number of cells and nuclei in a mature embryo sac?Show answer

   7 cells, 8 nuclei.

3. 3.What is triple fusion?Show answer

   Fusion of a male gamete with two polar nuclei to form the 3n primary endosperm nucleus.

4. 4.Define xenogamy.Show answer

   Transfer of pollen to the stigma of a flower on a different plant of the same species.

5. 5.What is perisperm?Show answer

   Persistent remnant of the nucellus in a seed (black pepper, beet).

6. 6.Name the shield-shaped cotyledon of maize.Show answer

   Scutellum.

7. 7.What is parthenocarpy?Show answer

   Development of fruit without fertilisation (seedless fruit).

8. 8.Function of filiform apparatus?Show answer

   Guides the pollen tube into the synergid.

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Can you draw and label T.S. of anther and L.S. of anatropous ovule?
• ☐Can you list the four wall layers of a microsporangium with functions?
• ☐Can you describe the 7-celled, 8-nucleate embryo sac?
• ☐Can you explain autogamy, geitonogamy and xenogamy, and chasmogamy and cleistogamy?
• ☐Can you name three outbreeding devices with examples?
• ☐Can you describe emasculation and bagging?
• ☐Can you work out ploidy of embryo, endosperm and seed coat for any cross?
• ☐Can you distinguish albuminous/non-albuminous seeds and true/false fruits?

Sexual Reproduction in Flowering Plants: frequently asked questions