Q.What is pollination? What are the kinds of pollination? Describe the different agents of pollination process.
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Start your 14-day free trial to unlock the full solution →Pollination transfers pollen from anther to stigma by self- or cross-pollination, via abiotic or biotic agents. OR: the pollen tube reaches the embryo sac through the micropyle, and the mature embryo sac has 7 cells/8 nuclei.
Pollination is the transfer of pollen grains from the anther (the male reproductive part) to the stigma (the receptive surface of the female reproductive part) of a flower.
Kinds of pollination: (1) Autogamy (self-pollination) — transfer of pollen from the anther to the stigma of the same flower. (2) Geitonogamy — transfer of pollen from the anther of one flower to the stigma of a different flower on the same plant; genetically this is similar to autogamy, but it functionally requires a pollinating agent, like cross-pollination. (3) Xenogamy — transfer of pollen from the anther of a flower on one plant to the stigma of a flower on a genetically different plant; this is true cross-pollination, bringing genetically different pollen to the stigma.
Agents of pollination: Abiotic agents include wind (anemophily, e.g., in grasses and maize) and water (hydrophily, e.g., in Vallisneria and Zostera). Biotic agents include insects (entomophily, e.g., bees and butterflies), birds (ornithophily, e.g., sunbirds and hummingbirds), bats (chiropterophily), and occasionally other animals such as snails.
OR:
(a) L.S. of pistil showing pollen tube growth: After pollination, the pollen grain germinates on the compatible stigma, and its intine grows out through a germ pore to form a pollen tube, which carries the two male gametes. The pollen tube grows down through the tissue of the style (either intercellularly or by digesting its way through) and enters the ovary, where it usually enters an ovule through the micropyle (a mode called porogamy) and finally penetrates one of the synergids of the embryo sac to release its two male gametes, enabling double fertilization.
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