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A pollen grain in angiosperm at the time of dehiscence from an anther could be 2-celled or 3-celled. Explain. How are the cells placed within the pollen grain when shed at a 2-celled stage ? |
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Answer» Every cell of the sporogenous tissue is a potential pollen mother cell (PMC) and can give rise to microspore tetrad,/pollen grains. Each microspore mother cell undergoes meiosis to form a cluster of four haploid cells, called microspore tetrad. As the anther matures, the microspores dissociates from one another from the tetrad and develop into pollen grains. The pollen grains are liberated at the two-celled stage in60% of angiosperms. In other species, the generative cell divides mitoticaily to form two male gametes and the pollen grains are three-celled during liberation. A mature pollen grain is two ceiled with a large vegetative cell and a small generative cell floating in cytoplasm of the vegetative cell. Vegetalive cell is bigger in size having abundant food reserve and a large irregularly shaped nucleus. |
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