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Question
Why does self-pollination not lead to seed formation in self-incompatible species?
Solution
Self-incompatibility is a gene-physiological event. A single gene, known as the S-gene, regulates incompatibility reactions and contains many alleles. Pollen grains that have the S-allele, which is shared by any of the two alleles found in pistil cells, will not function on that pistil. However, any pollen grain that does not share any S alleles with the pistil of that plant will be functional on the pistil. Self pollens are unable to fertilise the egg, resulting in the formation of an embryo, hence seeds do not form in incompatible species.
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