Sexual Reproduction in Flowering Plants NEET Notes 2027 with PDF

Sexual Reproduction in Flowering Plants is Chapter 1 of NCERT Class 12 Biology and part of Unit 6, Reproduction, of the NEET UG syllabus. These notes cover the stamen and pollen grain, the ovule and embryo sac, pollination, outbreeding devices, pollen-pistil interaction, double fertilisation, endosperm, embryo, seed and fruit, apomixis and polyembryony, with a free notes PDF.

Sexual Reproduction in Flowering Plants NEET Notes

Section-wise key points from NCERT Chapter 1, comparison tables, high-yield facts and common mistakes for NEET 2027 revision.

Sexual Reproduction in Flowering Plants at a Glance

The topic list follows the NEET UG 2026 syllabus released by the National Medical Commission (NMC) on 22 December 2025, which stays the reference until the 2027 syllabus is out. The full list is on the NEET syllabus page.

Flower: the Seat of Sexual Reproduction

Flowers are the site of sexual reproduction in angiosperms: the androecium (whorl of stamens) is the male reproductive organ and the gynoecium (pistil) is the female reproductive organ.

• The decision to flower is taken well before the flower appears; hormonal and structural changes lead to differentiation of the floral primordium.
• Inflorescences bear floral buds and then flowers, in which the androecium and gynoecium differentiate.
• All flowering plants show sexual reproduction, and its end products are fruits and seeds.

Stamen, Microsporangium and Pollen Grain

A stamen has a long slender filament and a terminal, generally bilobed anther; pollen grains develop inside the four microsporangia of the anther.

• A typical anther is bilobed, each lobe has two theca (dithecous), and it has four microsporangia at the corners, two in each lobe (tetrasporangiate).
• Microsporangia develop into pollen sacs packed with pollen grains.
• Microsporogenesis: cells of the sporogenous tissue act as pollen mother cells (PMC) and undergo meiosis to form microspore tetrads. As the anther matures and dehydrates, microspores separate and develop into pollen grains.

Pollen Grain: the Male Gametophyte

• Generally spherical, about 25 to 50 micrometres in diameter, with a two-layered wall.
• Exine: hard outer layer of sporopollenin, one of the most resistant organic materials known; it withstands high temperature, strong acids and alkali, and no enzyme that degrades it is known. Pollen is well preserved as fossils because of it.
• Germ pores are apertures in the exine where sporopollenin is absent.
• Intine: thin, continuous inner wall of cellulose and pectin.
• Mature pollen has a large vegetative cell (food reserve, large irregular nucleus) and a small spindle-shaped generative cell floating in it.
• In over 60 per cent of angiosperms pollen is shed at this 2-celled stage; in the rest the generative cell divides mitotically into two male gametes before shedding (3-celled stage).
• Pollen of many species causes allergies; Parthenium (carrot grass), which came into India with imported wheat, causes pollen allergy.
• Viability: rice and wheat pollen lose it within 30 minutes; some Rosaceae, Leguminoseae and Solanaceae pollen stay viable for months. Pollen can be stored for years in liquid nitrogen (-196 °C) in pollen banks.

Pistil, Ovule and Embryo Sac

Each pistil has a stigma (landing platform for pollen), a style and an ovary; ovules (megasporangia) arise from the placenta inside the ovarian cavity.

• Gynoecium may be monocarpellary or multicarpellary; multicarpellary pistils may be fused (syncarpous, e.g. Papaver) or free (apocarpous, e.g. Michelia).
• Number of ovules: one (wheat, paddy, mango) to many (papaya, water melon, orchids).

Megasporogenesis and the Female Gametophyte

• A single megaspore mother cell (MMC) differentiates in the micropylar region of the nucellus and undergoes meiosis to form four megaspores.
• In most flowering plants one megaspore is functional and three degenerate. Embryo sac formation from a single megaspore is monosporic development.
• The functional megaspore nucleus divides mitotically three times (2, 4 and then 8-nucleate stages). These divisions are strictly free nuclear; cell walls form only after the 8-nucleate stage.
• Six of the eight nuclei get cell walls; the remaining two, the polar nuclei, lie in the large central cell below the egg apparatus.
• So a mature angiosperm embryo sac is 8-nucleate but 7-celled.

Pollination: Kinds and Agents

Pollination is the transfer of pollen grains from the anther to the stigma of a pistil; it is needed because both male and female gametes are non-motile.

• Viola (common pansy), Oxalis and Commelina have chasmogamous flowers (open, exposed anthers and stigma) and cleistogamous flowers (never open).
• Cleistogamous flowers are invariably autogamous and give assured seed-set even without pollinators.

Agents of Pollination

• In Vallisneria the female flower reaches the water surface on a long stalk and male flowers or pollen float to it; in seagrasses pollination happens under water.
• Not all aquatic plants use water: water hyacinth and water lily flowers rise above the water and are pollinated by insects or wind.
• Wind- and water-pollinated flowers are not very colourful and do not produce nectar. Both produce huge amounts of pollen to make up for chance losses.
• Floral rewards are usually nectar and pollen. Amorphophallus (flower about 6 feet tall) and Yucca offer a safe place to lay eggs; Yucca and its moth cannot complete their life cycles without each other.
• Insects that take pollen or nectar without pollinating are pollen/nectar robbers.

Outbreeding Devices

Continued self-pollination causes inbreeding depression, so flowering plants have devices that discourage self-pollination and encourage cross-pollination.

Pollen-pistil Interaction and Artificial Hybridisation

Pollen-pistil interaction is all the events from pollen deposition on the stigma until the pollen tube enters the ovule; the pistil recognises compatible pollen and rejects the wrong type.

• The recognition is a dialogue mediated by chemical components of the pollen interacting with those of the pistil.
• Incompatible pollen is rejected by preventing its germination on the stigma or pollen tube growth in the style.
• Compatible pollen germinates and the pollen tube emerges through one of the germ pores, grows through the stigma and style and reaches the ovary.
• In plants that shed 2-celled pollen, the generative cell divides into two male gametes while the pollen tube grows in the stigma.
• The tube enters the ovule through the micropyle and then a synergid through the filiform apparatus, which guides its entry.
• Pollen germination can be seen by dusting pollen of pea, chickpea, Crotalaria, balsam or Vinca on a drop of about 10 per cent sugar solution; tubes appear in 15 to 30 minutes.

Emasculation and Bagging

• Artificial hybridisation is a major crop-improvement approach; only the desired pollen should reach the stigma.
• Emasculation: removing anthers from the flower bud of a bisexual female parent, before the anthers dehisce, using forceps.
• Bagging: covering the emasculated flower with a bag, generally of butter paper, to keep unwanted pollen off the stigma. When the stigma is receptive, desired pollen is dusted on it and the flower is rebagged.
• If the female parent has unisexual flowers, emasculation is not needed; female buds are simply bagged before they open.

What is double fertilisation?

Double fertilisation is the occurrence of two fusions, syngamy and triple fusion, in the same embryo sac; it is an event unique to flowering plants.

• The pollen tube releases two male gametes into the cytoplasm of a synergid.
• Syngamy: one male gamete fuses with the egg nucleus to form the diploid zygote.
• Triple fusion: the other male gamete fuses with the two polar nuclei in the central cell to form the triploid primary endosperm nucleus (PEN), because three haploid nuclei fuse.
• The central cell becomes the primary endosperm cell (PEC), which develops into the endosperm; the zygote develops into the embryo.

Post-fertilisation Events: Endosperm, Embryo, Seed and Fruit

After double fertilisation, endosperm and embryo develop, ovules mature into seeds and the ovary into a fruit; together these are the post-fertilisation events.

Endosperm

• Endosperm development always comes before embryo development, so the embryo gets assured nutrition.
• The PEC divides repeatedly to form triploid endosperm tissue filled with reserve food.
• In the most common type, the PEN gives rise to free nuclei first (free-nuclear endosperm), then cell walls form and it becomes cellular.
• Tender coconut water is free-nuclear endosperm (thousands of nuclei); the white kernel is cellular endosperm.
• Endosperm is fully used up before seed maturation in pea, groundnut and beans, but persists in castor and coconut.

Embryo

• The embryo develops at the micropylar end, where the zygote lies; most zygotes divide only after some endosperm has formed.
• Stages: zygote, proembryo, globular, heart-shaped and mature embryo. Early stages are similar in monocots and dicots.

Seed and Fruit

• The seed is the final product of sexual reproduction, often described as a fertilised ovule; it has seed coat(s), cotyledon(s) and an embryo axis.
• Non-albuminous seeds have no residual endosperm (pea, groundnut). Albuminous seeds retain part of it (wheat, maize, barley, castor).
• Perisperm is residual, persistent nucellus, seen in black pepper and beet.
• Integuments harden into seed coats; the micropyle stays as a pore that lets in oxygen and water at germination.
• Mature seeds dry to 10 to 15 per cent moisture by mass; the embryo may enter dormancy or germinate if moisture, oxygen and temperature are suitable.
• The ovary wall becomes the fruit wall, the pericarp. Fruits may be fleshy (guava, orange, mango) or dry (groundnut, mustard).
• False fruits get a contribution from the thalamus (apple, strawberry, cashew); true fruits develop only from the ovary.
• Parthenocarpic fruits develop without fertilisation and are seedless (banana); parthenocarpy can be induced with growth hormones.
• Advantages of seeds: pollination and fertilisation are independent of water; better dispersal; food reserves for seedlings; hard seed coat; new genetic combinations.
• Old viable seeds: Lupinus arcticus from the Arctic tundra germinated after an estimated 10,000 years; a 2000-year-old date palm (Phoenix dactylifera) seed was found at King Herod’s palace near the Dead Sea.
• Orchid fruits, and those of the parasites Orobanche and Striga, contain thousands of tiny seeds.

Apomixis and Polyembryony

Apomixis is the production of seeds without fertilisation; it is a form of asexual reproduction that mimics sexual reproduction, found in some Asteraceae and grasses.

• In some species a diploid egg cell forms without reduction division and develops into an embryo without fertilisation.
• More often, as in many Citrus and mango varieties, nucellar cells around the embryo sac divide, protrude into it and develop into embryos.
• Polyembryony is the occurrence of more than one embryo in a seed; squeezing orange seeds shows several embryos of different sizes.
• Hybrid seeds must be bought every year because their progeny segregate. If hybrids are made apomictic, there is no segregation, so farmers could reuse hybrid seed; research aims to transfer apomictic genes into hybrid varieties.

Most-asked Facts for NEET: Sexual Reproduction in Flowering Plants

Revise these one-line facts from the NCERT chapter just before the exam.

• Anther: bilobed, dithecous and tetrasporangiate.
• Tapetum is the innermost wall layer and nourishes developing pollen.
• Exine is made of sporopollenin; germ pores lack it. Intine is cellulose and pectin.
• Pollen is shed at the 2-celled stage in over 60 per cent of angiosperms.
• Pollen can be stored in liquid nitrogen at -196 °C.
• Hilum is the junction of ovule and funicle; chalaza is the basal part opposite the micropyle.
• Monosporic development: embryo sac forms from a single functional megaspore.
• Mature embryo sac: 8-nucleate and 7-celled.
• Filiform apparatus of synergids guides the pollen tube.
• Cleistogamous flowers (Viola, Oxalis, Commelina) are invariably autogamous.
• Water pollination: Vallisneria, Hydrilla, Zostera.
• Dioecy (papaya) prevents both autogamy and geitonogamy.
• Triple fusion gives the triploid primary endosperm nucleus.
• Coconut water is free-nuclear endosperm; the kernel is cellular endosperm.
• Grass embryo: scutellum, coleoptile and coleorrhiza.
• Perisperm (persistent nucellus) occurs in black pepper and beet.
• False fruits: apple, strawberry, cashew. Parthenocarpic fruit: banana.
• Polyembryony from nucellar cells occurs in Citrus and mango.

Common Mistakes to Avoid

Watch for these mix-ups when you answer questions on this chapter.

• Calling the mature embryo sac 8-celled. It is 8-nucleate but 7-celled, because the two polar nuclei share the central cell.
• Placing the synergids at the chalazal end. The egg apparatus is at the micropylar end; the antipodals are at the chalazal end.
• Saying geitonogamy brings genetic variation. It is functionally cross-pollination but genetically the same as autogamy.
• Saying monoecy prevents geitonogamy. Monoecy (castor, maize) prevents only autogamy; dioecy (papaya) prevents both.
• Calling the primary endosperm nucleus diploid. It is triploid, formed from three haploid nuclei.
• Thinking the embryo develops before the endosperm. Endosperm development always comes first.
• Mixing up perisperm (persistent nucellus in the seed) and pericarp (fruit wall formed from the ovary wall).
• Swapping coleoptile and coleorrhiza. The coleoptile covers the shoot apex; the coleorrhiza covers the radicle and root cap.
• Treating apomixis and parthenocarpy as the same. Apomixis forms seeds without fertilisation; parthenocarpy forms seedless fruits without fertilisation.
• Assuming all aquatic plants are water-pollinated. Water hyacinth and water lily are pollinated by insects or wind.

Sexual Reproduction in Flowering Plants Notes PDF and Related Pages

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• All chapters: NEET Biology notes
• Full topic list: NEET syllabus
• Practice: NEET question papers
• Source text: NCERT Chapter 1 (NCERT, Class 12 Biology)

NEET Biology Notes: All Chapters

Botany

• The Living World
• Biological Classification
• Plant Kingdom
• Cell: The Unit of Life
• Plant Growth and Development
• Anatomy of Flowering Plants
• Cell Cycle and Cell Division
• Respiration in Plants
• Photosynthesis in Higher Plants
• Morphology of Flowering Plants
• Principles of Inheritance and Variation
• Microbes in Human Welfare
• Sexual Reproduction in Flowering Plants
• Molecular Basis of Inheritance
• Organisms and Populations
• Ecosystem
• Biodiversity and Conservation

Zoology

• Animal Kingdom
• Biomolecules
• Breathing and Exchange of Gases
• Excretory Products and their Elimination
• Body Fluids and Circulation
• Structural Organisation in Animals
• Locomotion and Movement
• Reproductive Health
• Chemical Coordination and Integration
• Neural Control and Coordination
• Evolution
• Human Health and Disease
• Human Reproduction
• Biotechnology and its Applications
• Biotechnology: Principles and Processes

All chapters with their notes PDFs are on the NEET Biology notes page.

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