Sexual Reproduction In Flowering Plants: Complete Chapter Notes for NEET by PW

Sexual Reproduction in Flowering Plants can be challenging to revise because the chapter involves several connected stages, from gamete formation and pollination to fertilisation and seed development. Understanding the structures, sequence of events and differences between processes is essential for answering concept-based Biology questions.

PW offers Sexual Reproduction in Flowering Plants notes that bring together important concepts, tricks and PYQs to support your NEET preparation. Use the chapter notes alongside the video to revise the reproductive structures, understand key processes such as double fertilisation and revisit important examples before practising questions. 

Asexual And Sexual Reproduction

In asexual reproduction, one parent produces offspring without the fusion of gametes. The offspring are described as highly similar to the parent.

In sexual reproduction, male and female gametes fuse to form a zygote. Since two parents generally contribute gametes, it is also called biparental reproduction.

Flower And Sexual Reproduction

A flower is the reproductive structure of an angiosperm. Its essential whorls are:

• Androecium: Male reproductive whorl made of stamens

• Gynoecium: Female reproductive whorl made of carpels

The accessory whorls are:

• Calyx: Made of sepals

• Corolla: Made of petals

Most flowers are bisexual, containing both androecium and gynoecium. Flowers may attract pollinators through colour, fragrance, nectar, large size, or arrangement into an inflorescence.

Sexual reproduction occurs through three major stages:

1. Pre-Fertilisation: Microsporogenesis, megasporogenesis, and pollination

2. Fertilisation: Double fertilisation

3. Post-Fertilisation: Embryo, endosperm, seed, and fruit formation

The flower is both a morphological marvel and an embryological marvel because important reproductive and developmental events occur inside it.

Formation Of The Flower

Cells of the shoot apical meristem become specialised into a floral meristem. The floral meristem produces the calyx, corolla, androecium, and gynoecium.

During flower formation:

• Internodal length decreases.

• Floral parts develop close to one another.

• A flower bud develops into a complete flower.

• Several flowers may form an inflorescence.

Flower formation involves hormonal and structural changes. The hormones mentioned are:

• Ethylene: Initiates flowering

• Auxin: Promotes flowering

• Florigen: Assists floral formation

Androecium And Anther Structure

The androecium consists of all the stamens in a flower. Each stamen has:

• Anther: Upper, rounded part

• Filament: Slender stalk supporting the anther

The filament may be attached to the thalamus, petal, or perianth.

• Attachment to a petal is called epipetalous, common in Solanaceae.

• Attachment to a tepal or perianth is called epiphyllous or epitepalous, common in Liliaceae.

Anthers are generally bilobed. Each lobe contains two thecae, giving a total of four thecae in one anther. Such an anther is called tetrathecous. The tissue connecting the two lobes is the connective.

Theca, Microsporangium, And Pollen Sac

The same chamber receives different names according to its contents:

• It is a theca when it contains sporogenous cells.

• It is a microsporangium when it contains microspores.

• It is a pollen sac when it contains mature pollen grains.

(*Memory Tip: Theca to Microsporangium to Pollen Sac follows sporogenous cells to microspores to pollen grains.)*

When the anther matures, a weak longitudinal line develops between the two thecae of each lobe. The anther splits along this line in dehiscence and releases pollen grains.

Microsporangium Wall Layers

From outside to inside, the four layers of a microsporangium are:

1. Epidermis

2. Endothecium

3. Middle Layers

4. Tapetum

The epidermis, endothecium, and middle layers mainly provide protection and assist in anther dehiscence. The tapetum is the innermost layer and provides nourishment to developing sporogenous cells, microspores, and pollen grains.

Microsporogenesis And Pollen Development

Microsporogenesis is the formation of microspores from sporogenous cells. A sporogenous cell is diploid and may also be called a pollen mother cell, microspore mother cell, or potential pollen.

The microspore mother cell undergoes meiosis and produces four haploid microspores. These remain attached as a microspore tetrad due to callose. As the anther dries, callose breaks down, and individual microspores become pollen grains.

(*Memory Tip: One diploid mother cell undergoes meiosis to form four haploid microspores, which first form a tetrad and then separate into pollen grains.)*

A pollen grain is the male gametophyte, not the male gamete. It divides asymmetrically into:

• Vegetative Cell: Larger, nutrient-rich, and supports pollen development

• Generative Cell: Smaller, spindle-shaped, and forms two male gametes

(*Memory Tip: The vegetative cell is large and supports development, while the generative cell generates the male gametes.)*

The generative cell undergoes mitosis and produces two male gametes. In about 60 percent of angiosperms, pollen is released at the two-celled stage. In about 40 per cent, it is released at the three-celled stage after the generative cell has divided.

Pollen Grain Wall And Germ Pore

From inside to outside, the pollen wall consists of:

1. Cell Membrane

2. Intine

3. Exine

The intine is continuous and contains cellulose and pectose. The exine contains sporopollenin, a highly resistant substance that withstands acids, bases, enzymes, and high temperatures.

The exine has a small opening called the germ pore. The pollen tube emerges through this opening. Surface patterns of pollen grains are caused by variations in the exine.

Pollen viability depends mainly on temperature and humidity. Rice and wheat pollen may remain viable for about 30 minutes, while pollen of Rosaceae, Solanaceae, and Leguminosae may remain viable for several months. Pollen can be stored at very low temperatures through cryopreservation.

Gynoecium, Ovary, And Ovule

The gynoecium consists of all carpels in a flower. A carpel has three parts:

• Stigma: Receives pollen

• Style: Passage for pollen tube growth

• Ovary: Swollen basal region containing ovules

A flower with one carpel is monocarpellary. A flower with several carpels is multicarpellary. Fused carpels form a syncarpous gynoecium, as in Papaver, while free carpels form an apocarpous gynoecium, as in Michelia.

The cavity of the ovary is the ovarian locule. The placenta is a cushion-like structure inside the ovary, and ovules are attached to it. An ovule is also called a megasporangium.

The ovule contains:

• Funicle: Connects the ovule to the placenta

• Hilum: Point of attachment of funicle to ovule body

• Integuments: Protective coverings

• Nucellus: Central nutritive tissue

• Chalaza: Basal region

• Micropyle: Opening at the opposite end

After fertilisation, the ovule becomes a seed, and the ovary becomes a fruit.

Megasporogenesis And Embryo Sac Formation

A diploid megaspore mother cell near the micropylar end undergoes meiosis and forms four haploid megaspores. Three degenerate, and one remains functional. This is called monosporic development.

The functional megaspore undergoes three mitotic divisions to form eight nuclei. Four nuclei move to each pole. Cell walls later develop to form the mature embryo sac.

The mature embryo sac is the female gametophyte and contains seven cells and eight nuclei:

• Three antipodal cells at the chalazal end

• Two synergids and one egg cell at the micropylar end

• One central cell containing two polar nuclei

The egg cell and two synergids form the egg apparatus. Synergids contain a filiform apparatus, which guides the pollen tube towards the egg apparatus.

Pollination Types

Pollination is the transfer of pollen grains to the stigma.

Cleistogamous flowers remain closed and are invariably autogamous. Viola, Oxalis, and Commelina produce cleistogamous flowers. Chasmogamous flowers are open and may permit external pollen transfer.

Major pollinating agents follow this order:

Biotic Agents > Wind > Water

Pollination by insects is entomophily, by birds is ornithophily, by bats is chiropterophily, by wind is anemophily, and by water is hydrophily.

Wind-pollinated flowers usually have exposed stamens, light and non-sticky pollen, inflorescences, and large feathery stigmas. Water-pollinated plants such as Vallisneria and Hydrilla show surface pollination, while Zostera shows submerged pollination.

Outbreeding Devices And Artificial Hybridisation

Outbreeding devices reduce self-pollination and promote xenogamy:

• Protandry: Anther matures before stigma

• Protogyny: Stigma matures before anther

• Different positions of anther and stigma

• Self-Incompatibility: Genetic rejection of unsuitable pollen

• Unisexual flowers

Self-incompatibility can prevent both autogamy and geitonogamy. In papaya, male and female flowers occur on separate plants, making xenogamy necessary.

Artificial hybridisation follows this sequence:

Emasculation, Bagging, Controlled Pollination, Rebagging

Emasculation is needed in bisexual flowers but not in female unisexual flowers. Bagging prevents contamination by unwanted pollen.

Double Fertilisation

Double fertilisation is a defining feature of angiosperms. Two male gametes enter the embryo sac through one synergid.

• One male gamete fuses with the egg to form a diploid zygote. This is syngamy.

• The second male gamete fuses with two polar nuclei to form the triploid primary endosperm nucleus. This is triple fusion.

The zygote develops into the embryo, and the primary endosperm nucleus develops into the endosperm.

Post-Fertilisation Changes

• Zygote becomes embryo

• Primary endosperm nucleus becomes endosperm

• Ovule becomes seed

• Ovary becomes fruit

• Outer integument becomes testa

• Inner integument becomes tegmen

• Micropyle remains as an opening in the seed

The endosperm develops before the embryo because it supplies nourishment. Endosperm may be free-nuclear or cellular.

Most dicot seeds are non-endospermic, while most monocot seeds are endospermic. Important exceptions are castor, a dicot with endosperm, and orchid, a monocot without endosperm. Persistent nucellus is called perisperm, found in black pepper and beet.

Embryo Development And Seed Types

The embryo develops through zygote, pro-embryo, globular, heart-shaped, and mature stages.

A dicot embryo has two cotyledons, plumule, radicle, epicotyl, and hypocotyl. A monocot embryo has one shield-shaped cotyledon called the scutellum, an epiblast, plumule, radicle, coleoptile, and coleorhiza.

A true fruit develops only from the ovary. Apple, strawberry, and cashew are false fruits because other floral parts also contribute. Parthenocarpy produces fruits without fertilisation, as in banana and seedless grapes.

Apomixis is seed formation without fertilisation. It helps maintain desirable hybrid characters without genetic segregation. Polyembryony is the formation of multiple embryos in one ovule, observed in some varieties of mango and citrus.

Watch PW’s SEXUAL REPRODUCTION IN FLOWERING PLANTS in ONE SHOT | All Concepts, Tricks & PYQs | NEET 2026 to revise the chapter’s important concepts, tricks and previous year questions. Revisit pollination, fertilisation, embryo and seed development, along with other key topics, to strengthen your understanding and identify areas that need further revision.

Sexual Reproduction in Flowering Plants becomes easier to revise when you connect each stage, from gamete formation to seed development, and understand the role of each reproductive structure. Revise the key concepts, focus on important examples and practise questions regularly. PW’s one-shot video can help you revisit important concepts, tricks and PYQs as part of your NEET Biology preparation.

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