Reproduction, pollination and fertilisation

Modes of reproduction in crop plants.

Agriculture6 questions
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How crop plants reproduce

Sexual reproduction produces seed through fusion of male and female gametes; offspring vary. Asexual (vegetative) reproduction uses parts other than seed and gives offspring identical to the parent: sugarcane (stem setts), potato (tubers), banana (suckers), sweet potato (vine cuttings). Apomixis is seed formation without fertilisation; it keeps hybrid vigour fixed.

Pollination is the transfer of pollen from anther to stigma.

  • Self-pollination (autogamy): pollen reaches the stigma of the same flower or plant. Crops: wheat, rice, barley, gram, pea, groundnut. Cleistogamy (flowers that do not open) ensures it.
  • Cross-pollination (allogamy): pollen comes from another plant. Crops: maize, pearl millet, sunflower, mustard (partly), cucurbits.
  • Agents: wind (anemophily: maize, wheat), insects (entomophily: sunflower, mustard), water and animals.

Devices that promote cross-pollination:

  • Dichogamy: anthers and stigma mature at different times. Protandry (anthers first: maize, sunflower); protogyny (stigma first: pearl millet).
  • Monoecy: separate male and female flowers on one plant (maize: tassel male, ear female; cucurbits).
  • Dioecy: male and female plants separate (papaya, date palm).
  • Self-incompatibility (cabbage, radish) and male sterility (used in hybrid seed production).

Double fertilisation (unique to flowering plants): the pollen tube brings two male gametes into the embryo sac. One fuses with the egg to form the zygote (2n) → embryo (syngamy). The other fuses with the two polar nuclei to form the primary endosperm nucleus (3n) → endosperm (triple fusion). After fertilisation, the ovule becomes the seed and the ovary becomes the fruit.

Key points

  • Self-pollinated: wheat, rice, gram; cross-pollinated: maize, pearl millet.
  • Protandry: maize; protogyny: pearl millet.
  • Dioecious: papaya, date palm.
  • Zygote 2n; endosperm 3n.

Exam tips

Common questions: ploidy of endosperm, example of a dioecious crop, meaning of protandry, and whether a crop is self- or cross-pollinated.

Common mistakes

  • Calling maize dioecious; it is monoecious.
  • Saying endosperm is diploid; in flowering plants it is triploid.

Practice questions

In flowering plants, the endosperm formed by triple fusion is:Easy
Papaya, which commonly has separate male and female plants, is an example of a:Easy
In maize, pollen is shed before the silks of the same plant are receptive. This is called:Medium
Which crop is normally self-pollinated?Medium
Formation of seed without fertilisation is called:Hard

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