Biology · Sexual Reproduction in Flowering Plants · NEET
No. Self-pollination is the transfer of pollen from an anther to the stigma of the same flower or same plant. Self-incompatibility is what happens after that pollen lands — the pistil recognises the pollen as genetically its own and blocks it. So self-pollination can still occur, but self-incompatibility stops it from ending in fertilisation. One is the pollen movement; the other is the genetic rejection.
Because the pistil inhibits its own pollen after pollination. The self-incompatibility genes cause the pollen either to fail to germinate on the stigma or the pollen tube to stop growing in the style. Since the pollen tube never reaches the ovule, the male gametes never fuse with the egg, so there is no fertilisation and therefore no seed. The pollen is healthy; the block is genetic, not a fault in the pollen.
Yes. NCERT lists self-incompatibility as one of the devices flowering plants evolved to prevent self-pollination from producing seed and to force cross-pollination. Continued self-pollination causes inbreeding depression, so preventing self-fertilisation keeps the population genetically varied. It is the strongest of the outbreeding devices because it acts even when self-pollen physically reaches the stigma.
This is part of pollen-pistil interaction. The pistil has the ability to recognise whether the pollen is compatible (right type) or incompatible (wrong type) through a chemical dialogue between molecules on the pollen and in the pistil. If the pollen carries the same self-incompatibility genes as the pistil, the pistil rejects it and no post-pollination events follow. For NEET, remember: recognition is the key idea, and it is genetically controlled.
No, this is a common trap. The pollen is fully viable and can successfully fertilise a genetically different plant of the same species. It only fails on the same plant. Self-incompatibility is a recognition-and-rejection system, not a defect in the pollen. That is why the same pollen works in cross-pollination but not in self-pollination.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
It is a genetic system in which a flower's pistil rejects pollen from the same flower or the same plant, so self-pollen cannot fertilise the egg and no seed is formed, even though the pollen is healthy.
To prevent self-fertilisation and force cross-pollination. Continued self-pollination causes inbreeding depression, so this device keeps the offspring genetically varied and stronger.
After pollination but before fertilisation. The pistil either prevents the pollen from germinating on the stigma or stops the pollen tube from growing through the style, so the male gametes never reach the egg.
It is a genetic barrier. Unlike unisexual flowers or non-synchronised pollen release, which are physical or timing barriers, self-incompatibility works through genetic recognition between the pollen and the pistil.
Yes, but only on a genetically different plant of the same species. The pollen is viable, so cross-pollination succeeds even though self-pollination is blocked.
