What is self-incompatibility? Why does self-pollination not lead to seed formation in self-incompatible species?
Self-incompatibility is a genetic mechanism developed by flowering plants to prevent inbreeding. It prevents self-pollen (from the same flower or other flowers of the same plant) from fertilising the ovules.
Self-pollination does not lead to seed formation in these species because the mechanism prevents fertilisation by inhibiting pollen germination or pollen tube growth in the pistil. Without the growth of the pollen tube, the male gametes cannot reach the ovule.
Explanation
The textbook describes self-incompatibility as a genetic method to discourage self-pollination. The answer identifies it as a mechanism that prevents self-pollen from effecting fertilisation. The second part explains the physiological reason: the inhibition of pollen germination or pollen tube growth within the pistil, which stops the fertilisation process required for seed formation.