Flower: Gametogenesis and Pollination
Flower is the reproductive organ of the plant. Microsporogenesis takes place inside anther, the microsporophyll or the male reproductive organ. The process of development of microspores inside the microsporangium (pollen chambers) from its sporogenous tissue is called microsporogenesis. The process of development of megaspores from the megaspore mother cells is called megasporogenesis and takes place inside the nucleus of developing ovule or the megasporangium. Pollen is a mass of microspores in a seed plant, which generally appear like a fine dust. Each pollen grain is a small body, of varying shape and structure. Pollination is the process of transfer of pollen grains from the anther to the stigma of the flower. Self pollination and cross pollination are the two major types of pollination. Autogamy is the transfer of pollen grains from the anther to the stigma of the same flower. Geitonogamy is the transfer of pollen grains from the anther of one flower to the stigma of another flower borne on same plant. Xenogamy nis the transfer of pollen grains from the anther to the stigma of a flower borne on different plant. Based on the agents, cross pollination may be Hydrophily (water), zoophily (animal), anemophily (wind), entomophily (insects) are several methods of pollination. Ornithophily (through birds), Chiropterophily (through bats) and Malacophily (through snails)are various methods of zoophily. Self pollination results in pure lines while cross pollination results in hybrids, hence variations. As soon as the pollen grain lands on a stigma, the stigma releases chemical signals (esterases and acid phosphatases) to judge the familiarity of the pollen. Artificial hybridisation is carried out in order to develop the plants with desired characters. The different methods involved in artificial hybridisation are emasculation, bagging and dusting.
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