By Rajesh Sahu, Botany faculty at Pramana Institute (25 years teaching NEET, ex-Allen, ex-Aakash)
This was the single biggest Biology chapter in NEET 2025, with about 10 questions by published analyses. Almost every question is a direct NCERT line: a wall layer, a number, an example plant. This page lists the lines that are asked again and again, so you can revise the whole chapter in 15 minutes.
Male side: stamen and pollen
- A typical anther is bilobed and dithecous, with four microsporangia.
- The microsporangium wall has four layers: epidermis, endothecium, middle layers and tapetum. The tapetum is the innermost layer and nourishes the developing pollen; its cells often have more than one nucleus.
- Microsporogenesis: each microspore mother cell divides by meiosis to form a tetrad of microspores, which become pollen grains.
- The pollen wall has two layers. The exine is made of sporopollenin, the most resistant organic material known; no enzyme degrades it. Germ pores are gaps where sporopollenin is absent. The intine is made of cellulose and pectin.
- A mature pollen grain has a large vegetative cell and a small generative cell. In over 60% of angiosperms, pollen is shed at this 2-celled stage; in the rest, the generative cell has already divided into two male gametes (3-celled stage).
- Pollen of rice and wheat stays viable for about 30 minutes; some families (Rosaceae, Leguminosae, Solanaceae) stay viable for months. Pollen can be stored in liquid nitrogen at −196 °C.
Female side: ovule and embryo sac
- Megasporogenesis: the megaspore mother cell divides by meiosis to form four megaspores. Usually only one survives (monosporic development).
- The functional megaspore nucleus divides three times by mitosis, giving an 8-nucleate, 7-celled embryo sac.
- At the micropylar end is the egg apparatus: two synergids and one egg cell. Synergids have a filiform apparatus that guides the pollen tube.
- Three antipodal cells sit at the chalazal end, and the large central cell holds two polar nuclei.
Pollination
| Type | Meaning |
|---|---|
| Autogamy | Pollen reaches the stigma of the same flower |
| Geitonogamy | Pollen reaches another flower of the same plant: cross-pollination in function, but genetically like autogamy |
| Xenogamy | Pollen reaches a flower of a different plant: the only type that brings new genes |
| Cleistogamous flowers | Never open, so they set seed even without pollinators (Viola, Oxalis, Commelina) |
| Agent | Key features and examples |
|---|---|
| Wind | Light, non-sticky pollen; exposed stamens; large feathery stigma; often one ovule per ovary; common in grasses; the maize tassel is the stigma and style |
| Water | Vallisneria, Hydrilla, Zostera (sea grass). Water hyacinth and water lily grow in water but are pollinated by insects or wind |
| Insects and animals | Large, colourful, fragrant, nectar-rich flowers. Yucca and its moth depend on each other |
Devices that prevent self-pollination: pollen release and stigma receptivity at different times, anther and stigma at different positions, self-incompatibility, and unisexual flowers. Monoecious plants such as castor and maize prevent autogamy but not geitonogamy; dioecious plants such as papaya prevent both.
Artificial hybridisation: emasculation (removing anthers before they shed pollen) and bagging (covering the flower to keep out unwanted pollen).
Fertilisation and after
- Double fertilisation: one male gamete fuses with the egg (syngamy), giving the diploid zygote. The other fuses with the two polar nuclei (triple fusion), giving the triploid primary endosperm nucleus.
- Endosperm develops before the embryo. Coconut water is free-nuclear endosperm, and the white kernel is cellular endosperm.
- Seeds with endosperm left are albuminous (wheat, maize, barley, castor); seeds where it is used up are non-albuminous (pea, groundnut). Remaining nucellus is the perisperm (black pepper, beet).
- The oldest viable seed on record is a lupine (Lupinus arcticus) seed of about 10,000 years. A date palm seed of about 2,000 years was found at King Herod's palace near the Dead Sea.
- False fruits develop partly from the thalamus (apple, strawberry, cashew). Parthenocarpic fruits form without fertilisation (banana).
- Apomixis is seed formation without fertilisation (some grasses and Asteraceae). Polyembryony, more than one embryo in a seed, is common in citrus and mango.
FAQs
Which layer of the anther nourishes pollen? The tapetum, the innermost wall layer.
How many cells and nuclei does a typical embryo sac have? 7 cells and 8 nuclei.
Why is geitonogamy genetically similar to autogamy? Both pollen and stigma come from the same plant, so no new genes are added.
Revise NCERT Botany line by line with weekly tests in a batch of at most 40 at Pramana, Geeta Bhawan Square, Indore. See our NEET program and the NEET 90-Day Revision Program.
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