NCERT Solutions for Class 12 Biology Chapter 1: Sexual Reproduction in Flowering Plants (NCERT 2026–27)
These Class 12 Biology Chapter 1 solutions cover Sexual Reproduction in Flowering Plants from the NCERT textbook (session 2026–27). Every one of the 18 end-of-chapter Exercises questions is reproduced verbatim and answered in exam-ready prose, along with key concepts, extra questions, MCQs, assertion–reason items and FAQs — everything you need to master pre-fertilisation events, double fertilisation, the seed and apomixis.
Class: 12Subject: BiologyChapter: 1Name: Sexual Reproduction in Flowering PlantsExercises: 18 questionsSession: 2026–27
Chapter 1, Sexual Reproduction in Flowering Plants, traces the entire reproductive journey of an angiosperm from flower to seed. It begins with pre-fertilisation structures and events — the stamen, microsporangium and pollen grain on the male side, and the pistil, ovule (megasporangium) and embryo sac on the female side — together with microsporogenesis, megasporogenesis and the various kinds and agents of pollination. It then explains the angiosperm hallmark of double fertilisation (syngamy + triple fusion), followed by post-fertilisation events: development of the triploid endosperm and the embryo, maturation of the ovule into a seed and the ovary into a fruit. The chapter closes with apomixis (seed formation without fertilisation) and polyembryony, both important in modern agriculture and hybrid-seed technology.
Key Concepts & Definitions
Stamen & anther: The male reproductive unit. A typical anther is bilobed, dithecous and tetrasporangiate, with four wall layers — epidermis, endothecium, middle layers and the nourishing tapetum.
Microsporogenesis: Formation of haploid microspores (microspore tetrads) from a diploid pollen mother cell by meiosis.
Pollen grain: The male gametophyte; a two-layered wall of hard exine (sporopollenin, with germ pores) and inner intine (cellulose & pectin). Shed at the 2-celled or 3-celled stage.
Ovule (megasporangium): Bears the embryo sac. Parts include funicle, hilum, integuments, micropyle, chalaza and nucellus.
Megasporogenesis & embryo sac: The megaspore mother cell undergoes meiosis to give four megaspores; one functional megaspore forms the embryo sac (monosporic development). The mature embryo sac is 7-celled and 8-nucleate — egg apparatus (2 synergids + 1 egg) at the micropylar end, 3 antipodals at the chalazal end, and a central cell with 2 polar nuclei.
Pollination: Transfer of pollen from anther to stigma — autogamy, geitonogamy or xenogamy; agents are abiotic (wind, water) or biotic (animals).
Seed & fruit: Ovule → seed (seed coat, cotyledon(s), embryonal axis); ovary → fruit (wall = pericarp). False fruits, parthenocarpy, apomixis and polyembryony round off the chapter.
NCERT Exercises — Solutions
All 18 questions below are reproduced verbatim from the NCERT textbook; the answers are original and written in CBSE exam-ready style.
1. Name the parts of an angiosperm flower in which development of male and female gametophyte take place.
ANSWERThe male gametophyte (pollen grain) develops inside the microsporangia (pollen sacs) of the anther, which is part of the stamen (androecium).The female gametophyte (embryo sac) develops inside the ovule (megasporangium), which lies within the ovary of the pistil (gynoecium).
2. Differentiate between microsporogenesis and megasporogenesis. Which type of cell division occurs during these events? Name the structures formed at the end of these two events.
ANSWERMicrosporogenesis is the process of formation of haploid microspores from a diploid microspore (pollen) mother cell in the anther.Megasporogenesis is the process of formation of haploid megaspores from a diploid megaspore mother cell (MMC) in the ovule.Type of division: Both events occur by meiosis (reduction division).Structures formed: Microsporogenesis produces a tetrad of four microspores, all of which are usually functional and mature into pollen grains. Megasporogenesis produces four megaspores, of which (in most plants) only one functional megaspore survives while the other three degenerate.
3. Arrange the following terms in the correct developmental sequence: Pollen grain, sporogenous tissue, microspore tetrad, pollen mother cell, male gametes.
4. With a neat, labelled diagram, describe the parts of a typical angiosperm ovule.
ANSWERA typical anatropous ovule is a small structure attached to the placenta by a stalk and contains the embryo sac. Its main parts are:Funicle — the stalk that attaches the ovule to the placenta.Hilum — the junction where the body of the ovule fuses with the funicle.Integuments — one or two protective envelopes surrounding the ovule.Micropyle — a small opening at the tip where the integuments do not meet; it lies at the micropylar end.Chalaza — the basal part of the ovule, opposite the micropylar end.Nucellus — a mass of cells rich in reserve food, enclosed within the integuments; it houses the embryo sac.Embryo sac (female gametophyte) — located in the nucellus, generally formed from a single megaspore.Diagram to label: draw an oval ovule with funicle and hilum at the base, integuments enclosing the nucellus, micropyle at one end, chalaza at the other, and the 7-celled embryo sac inside the nucellus.
5. What is meant by monosporic development of female gametophyte?
ANSWERWhen the megaspore mother cell undergoes meiosis, four megaspores are produced, but in a majority of flowering plants only one of these megaspores remains functional and the other three degenerate.The formation of the embryo sac (female gametophyte) from this single functional megaspore is called monosporic development.
6. With a neat diagram explain the 7-celled, 8-nucleate nature of the female gametophyte.
ANSWERThe nucleus of the functional megaspore divides mitotically three times. These divisions are free-nuclear (not immediately followed by wall formation), producing successively the 2-nucleate, 4-nucleate and finally 8-nucleate stage.After the 8-nucleate stage, cell walls are laid down around six of the eight nuclei, organising them into 6 cells; the remaining two nuclei stay free as polar nuclei in the large central cell.Distribution: three cells form the egg apparatus (two synergids + one egg cell) at the micropylar end; three cells form the antipodals at the chalazal end; the central cell with two polar nuclei lies in the middle.Counting: 2 synergids + 1 egg + 3 antipodals + 1 central cell = 7 cells, but 8 nuclei (the central cell carries 2). Hence the mature embryo sac is 7-celled and 8-nucleate. (Diagram: label egg apparatus, synergids with filiform apparatus, central cell with two polar nuclei, and antipodals.)
7. What are chasmogamous flowers? Can cross-pollination occur in cleistogamous flowers? Give reasons for your answer.
ANSWERChasmogamous flowers are flowers that open and expose their anthers and stigma, like the normal flowers of most species, allowing both self- and cross-pollination.Cross-pollination cannot occur in cleistogamous flowers. Cleistogamous flowers never open at all; their anthers and stigma lie very close together. When the anthers dehisce inside the closed bud, the pollen falls directly onto the stigma of the same flower. Because the flower stays closed, there is no chance for pollen from another flower or plant to reach the stigma, so cleistogamous flowers are invariably autogamous (self-pollinated) and ensure assured seed-set even without pollinators.
8. Mention two strategies evolved to prevent self-pollination in flowers.
ANSWER1. Lack of synchrony in pollen release and stigma receptivity: the pollen is released before the stigma becomes receptive, or the stigma becomes receptive long before the pollen is released, so self-pollen cannot reach a receptive stigma of the same flower.2. Different positions of anther and stigma: the anther and stigma are placed at different positions in the flower so that pollen cannot fall on the stigma of the same flower. (Production of unisexual flowers and self-incompatibility are other accepted strategies.)
9. What is self-incompatibility? Why does self-pollination not lead to seed formation in self-incompatible species?
ANSWERSelf-incompatibility is a genetic mechanism that prevents self-pollen (from the same flower or other flowers of the same plant) from fertilising the ovules.In self-incompatible species, when self-pollen lands on the stigma, the pistil recognises it as “own” pollen and inhibits its germination on the stigma or the growth of the pollen tube in the style. Since the pollen tube cannot reach the ovule, the male gametes are never delivered, fertilisation does not occur, and therefore no seeds are formed by self-pollination.
10. What is bagging technique? How is it useful in a plant breeding programme?
ANSWERBagging is the technique of covering an emasculated flower (or a female flower bud) with a bag of suitable size, usually made of butter paper, to prevent its stigma from being contaminated by unwanted pollen.Usefulness: In artificial hybridisation, the breeder wants only desired pollen to fertilise the flower. Bagging keeps out stray, unwanted pollen. When the bagged stigma becomes receptive, the breeder dusts on mature pollen collected from the chosen male parent and rebags the flower, ensuring a controlled, pure cross that yields the intended hybrid.
11. What is triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.
ANSWERTriple fusion is the fusion of one male gamete with the two polar nuclei of the central cell, producing the triploid (3n) primary endosperm nucleus (PEN).Where: It takes place inside the central cell of the embryo sac, after the pollen tube discharges its two male gametes into a synergid.How: Of the two male gametes, one fuses with the egg (syngamy); the other moves towards the central cell and fuses with the two polar nuclei.Nuclei involved: one male gamete nucleus + two polar nuclei (three haploid nuclei in all — hence “triple” fusion).
12. Why do you think the zygote is dormant for sometime in a fertilised ovule?
ANSWERIn most plants the zygote divides only after a certain amount of endosperm has been formed; endosperm development always precedes embryo development.This delay (dormancy) is an adaptation to ensure assured nutrition for the developing embryo. By waiting until the nutritive endosperm tissue is ready, the embryo is guaranteed a continuous food supply during its growth, improving its chances of healthy development.
13. Differentiate between:
(a) hypocotyl and epicotyl;(b) coleoptile and coleorrhiza;(c) integument and testa;(d) perisperm and pericarp.
ANSWER
Term
Distinction
(a) Hypocotyl vs Epicotyl
Hypocotyl is the portion of the embryonal axis below the level of the cotyledons, ending in the radicle (root tip). Epicotyl is the portion above the cotyledons, ending in the plumule (stem tip).
(b) Coleoptile vs Coleorrhiza
Both are sheaths in a monocot (grass) embryo. The coleoptile is the hollow foliar sheath that protects the shoot apex/plumule. The coleorrhiza is the undifferentiated sheath that encloses the radicle and root cap.
(c) Integument vs Testa
The integument is the protective covering of the unfertilised ovule. After fertilisation, the integument hardens into the testa — the tough outer seed coat. (Integument → pre-fertilisation; testa → in the seed.)
(d) Perisperm vs Pericarp
The perisperm is the residual, persistent nucellus found in some seeds (e.g. black pepper, beet). The pericarp is the wall of the fruit, formed from the wall of the ovary.
14. Why is apple called a false fruit? Which part(s) of the flower forms the fruit?
ANSWERAn apple is called a false fruit because it does not develop only from the ovary. In apple (and strawberry, cashew, etc.), the thalamus grows and contributes the major fleshy, edible part of the fruit.Since a fruit forming purely from the ovary is a true fruit, an apple — with a large thalamic contribution — is termed a false fruit. Parts forming the fruit: mainly the thalamus, along with the ovary.
15. What is meant by emasculation? When and why does a plant breeder employ this technique?
ANSWEREmasculation is the removal of the anthers from a bisexual flower bud, using a pair of forceps, before the anthers dehisce.When: It is done in artificial hybridisation when the female parent bears bisexual (hermaphrodite) flowers, at the bud stage before pollen is shed.Why: By removing the anthers, the breeder prevents self-pollination of the flower so that its stigma can later be dusted only with the desired pollen of the chosen male parent — ensuring a controlled, intended cross. (For unisexual female flowers emasculation is unnecessary.)
16. If one can induce parthenocarpy through the application of growth substances, which fruits would you select to induce parthenocarpy and why?
ANSWERParthenocarpy is the development of fruit without fertilisation, producing seedless fruits. Therefore one would select fruits that are eaten directly as edible pulp and whose seeds are a nuisance to consumers.Good choices are banana, grapes, orange, watermelon, papaya and guava. Inducing parthenocarpy makes them seedless, which raises their market value, makes them easier and more pleasant to eat, and increases consumer demand — while still giving normal-looking, fleshy fruit.
17. Explain the role of tapetum in the formation of pollen-grain wall.
ANSWERThe tapetum is the innermost wall layer of the microsporangium. Its cells have dense cytoplasm and are usually multinucleate, reflecting their high metabolic activity.The tapetum nourishes the developing pollen grains and provides the material for the pollen-grain wall. In particular, it supplies sporopollenin — the highly resistant substance that makes up the hard outer exine — along with other materials needed for pollen development. Thus the tapetum is essential for the proper formation of the pollen-grain wall.
18. What is apomixis and what is its importance?
ANSWERApomixis is a form of asexual reproduction that mimics sexual reproduction — the production of seeds without fertilisation. It occurs in some species of Asteraceae and grasses (e.g. by a diploid egg developing without reduction division, or by nucellar cells developing into embryos).Importance: If hybrids are made apomictic, there is no segregation of characters in the progeny, so the desirable hybrid traits are retained generation after generation. Farmers could then re-use seeds collected from hybrid plants year after year instead of buying costly fresh hybrid seed every season, greatly reducing cost. Hence apomixis is of great value in the hybrid-seed industry and horticulture.
Extra Practice Questions
Short Answer Type Questions
Q1. Why is sporopollenin considered a remarkable substance?
ANSWERSporopollenin forms the exine of pollen grains and is one of the most resistant organic materials known. It can withstand high temperatures, strong acids and alkalis, and no enzyme is known to degrade it — which is why pollen grains are so well preserved as fossils.
Q2. Distinguish between geitonogamy and xenogamy.
ANSWERGeitonogamy is the transfer of pollen from the anther to the stigma of another flower of the same plant — functionally cross-pollination, but genetically like autogamy. Xenogamy is the transfer of pollen to the stigma of a different plant, and is the only type that brings genetically different pollen to the stigma.
Q3. Why is coconut water described as a stage of endosperm?
ANSWERCoconut water is free-nuclear endosperm — it is made up of thousands of free nuclei not yet enclosed by cell walls. The surrounding white kernel is the later cellular endosperm.
Q4. Define polyembryony and give an example.
ANSWERPolyembryony is the occurrence of more than one embryo in a single seed. It is commonly seen in many Citrus (e.g. orange) and Mango varieties, where nucellar cells develop into additional embryos.
Q5. What are the floral rewards offered to animal pollinators, and why are they needed?
ANSWERThe usual floral rewards are nectar and pollen grains; in some species safe egg-laying sites (as in Amorphophallus and Yucca) are offered. These rewards are needed to attract and sustain animal visits, during which the animal’s body picks up pollen and transfers it to the stigma, bringing about pollination.
Long Answer Type Questions
Q1. Describe the structure of a typical microsporangium and the process of microsporogenesis.
ANSWERIn transverse section a typical microsporangium is near circular and is surrounded by four wall layers — the epidermis, endothecium, middle layers and the innermost tapetum. The outer three layers protect the sporangium and help in dehiscence of the anther, while the tapetum nourishes the developing pollen grains. When the anther is young, a mass of compactly arranged sporogenous tissue occupies the centre of each microsporangium. As the anther matures, the cells of the sporogenous tissue act as pollen (microspore) mother cells and undergo meiosis — the process called microsporogenesis — each forming a cluster of four haploid microspores known as a microspore tetrad. As the anther dehydrates, the microspores separate and develop into pollen grains, with several thousand formed in each microsporangium and released on dehiscence of the anther.
Q2. Explain double fertilisation and trace the fate of its products.
ANSWERAfter the pollen tube enters a synergid, it releases two male gametes. Syngamy occurs when one male gamete fuses with the egg cell to form a diploid (2n) zygote. Triple fusion occurs when the second male gamete fuses with the two polar nuclei of the central cell to form a triploid (3n) primary endosperm nucleus (PEN). Because two fusion events — syngamy and triple fusion — take place within one embryo sac, the phenomenon is called double fertilisation, an event unique to flowering plants. Fate of products: the central cell (now the primary endosperm cell) develops into the nutritive endosperm tissue, and the zygote develops into the embryo. Since endosperm development precedes embryo development, the embryo is assured of nutrition.
Q3. Describe the post-fertilisation development of the seed and fruit in angiosperms.
ANSWERFollowing double fertilisation, several post-fertilisation events occur simultaneously. The primary endosperm cell divides repeatedly to form the triploid endosperm; in the common type, free nuclei form first (free-nuclear endosperm) before cell walls appear (cellular endosperm). The zygote, after some endosperm is formed, develops through proembryo, globular and heart-shaped stages into a mature embryo — a dicot embryo has two cotyledons with an embryonal axis (epicotyl above and hypocotyl below), while a monocot has a single cotyledon (scutellum) with coleoptile and coleorrhiza. Meanwhile the integuments harden into the seed coat, the micropyle persists as a small pore aiding entry of water and oxygen, and the seed dries to 10–15% moisture and may enter dormancy. As ovules mature into seeds, the ovary wall develops into the pericarp, forming the fruit. Where only the ovary forms the fruit it is a true fruit; where the thalamus contributes (apple, strawberry) it is a false fruit; and fruits formed without fertilisation (banana) are parthenocarpic.
Multiple Choice Questions (MCQs)
1. A typical angiosperm anther is:
(a) monothecous and tetrasporangiate (b) bilobed, dithecous and tetrasporangiate (c) bilobed and bisporangiate (d) unilobed and monosporangiate
2. The innermost wall layer of the microsporangium that nourishes the pollen grains is the:
For each question, choose: (A) Both true and the Reason correctly explains the Assertion; (B) Both true but the Reason is not the correct explanation; (C) Assertion true, Reason false; (D) Assertion false, Reason true.
A-R 1. Assertion: Pollen grains are well preserved as fossils.
Reason: The exine of the pollen grain is made of sporopollenin, a highly resistant organic material that no known enzyme can degrade.
A-R 2. Assertion: Cleistogamous flowers are always self-pollinated.
Reason: Cleistogamous flowers never open, so cross-pollen cannot reach their stigma.
A-R 3. Assertion: The mature embryo sac has eight cells.
Reason: After the 8-nucleate stage, all eight nuclei are surrounded by cell walls to form eight cells.
A-R 4. Assertion: In a fertilised ovule the zygote usually remains dormant for some time.
Reason: The zygote divides only after some endosperm is formed, ensuring assured nutrition for the embryo.
A-R 5. Assertion: Banana is a parthenocarpic fruit.
Reason: Parthenocarpic fruits develop from the ovary after fertilisation and are rich in seeds.
Answer key: 1-(A), 2-(A), 3-(C), 4-(A), 5-(C).
Common Mistakes to Avoid
Watch out for these
Saying the embryo sac is “8-celled” — it is 7-celled but 8-nucleate (the central cell holds two polar nuclei).
Confusing the products of fertilisation — syngamy gives the diploid zygote, triple fusion gives the triploid PEN/endosperm.
Mixing up geitonogamy and xenogamy — geitonogamy is between flowers of the same plant; xenogamy is between different plants.
Writing that all four megaspores form embryo sacs — in monosporic development only one functional megaspore survives.
Calling apomixis “sexual” — it is asexual reproduction that only mimics sexual reproduction (no fertilisation).
Confusing integument with testa, or perisperm with pericarp — learn each pair precisely.
How to score full marks in this chapter
Be precise with numbers and ploidy: tetrad of 4 microspores, 4 megaspores (1 functional), 7-celled/8-nucleate embryo sac, diploid zygote and triploid endosperm. For diagram questions (ovule, embryo sac), always give a neat labelled diagram — label funicle, integuments, micropyle, chalaza, nucellus, egg apparatus, synergids, antipodals and polar nuclei. Use the exact textbook terms (microsporogenesis, syngamy, triple fusion, monosporic, parthenocarpy, apomixis) and distinguish closely related pairs in clear, contrasting sentences.
Frequently Asked Questions
What is Class 12 Biology Chapter 1 about?
Chapter 1, Sexual Reproduction in Flowering Plants, explains the pre-fertilisation structures and events (stamen, pollen grain, pistil, ovule, embryo sac, microsporogenesis, megasporogenesis and pollination), double fertilisation (syngamy and triple fusion), post-fertilisation events (endosperm, embryo, seed and fruit), and apomixis and polyembryony.
Why is double fertilisation unique to angiosperms?
Because two fusion events occur within a single embryo sac — syngamy (one male gamete + egg → diploid zygote) and triple fusion (the other male gamete + two polar nuclei → triploid primary endosperm nucleus). This combination is found only in flowering plants.
How many exercise questions are solved on this page?
All 18 NCERT end-of-chapter Exercises questions are reproduced verbatim and answered in exam-ready prose, along with extra short and long questions, 10 MCQs and 5 assertion–reason items with answer keys.
Are these Class 12 Biology Chapter 1 solutions free?
Yes. All solutions are free and follow the official NCERT textbook for session 2026–27.
