Biology · Sexual Reproduction in Flowering Plants · NEET
Pollination is the transfer of pollen grains, shed from the anther, to the stigma of a flower. Because both the male gamete (inside pollen) and the female gamete (inside the embryo sac) are non-motile, pollination is the step that brings them close so fertilisation can happen. Remember: pollination is only the transfer of pollen, not fertilisation itself.
Sort them by the SOURCE of pollen. Autogamy = pollen from the same flower's own anther lands on its own stigma (same flower). Geitonogamy = pollen goes from the anther of one flower to the stigma of another flower on the SAME plant. Xenogamy = pollen goes to the stigma of a DIFFERENT plant. Use '1 flower, 1 plant, 2 plants' to lock the order.
This is the most common NEET trap. Geitonogamy is FUNCTIONALLY cross-pollination because it needs a pollinating agent (like an insect) to carry pollen from one flower to another. BUT genetically it is the same as autogamy (self-pollination), because both flowers belong to the same plant, so the pollen is genetically identical. Function = cross, genetics = self.
Only xenogamy. It is the only kind of pollination that brings genetically different types of pollen grains to the stigma, because the pollen comes from a genetically different plant. Autogamy and geitonogamy both use pollen from the same plant, so they are genetically self. This one NCERT line has been asked in multiple NEET years.
Autogamy is a type of pollination (pollen within the same flower). Cleistogamy describes flowers that never open (like in Viola, Oxalis, Commelina). Cleistogamous flowers are invariably autogamous because their closed petals stop any outside pollen from reaching the stigma, so self-pollination is guaranteed. So cleistogamy always leads to autogamy, but autogamy can also happen in open (chasmogamous) flowers.
No. In a normal flower that opens and exposes its anthers and stigma, complete autogamy is rather rare. It needs two things at the same time: the pollen must be released exactly when the stigma is receptive (synchrony), and the anthers and stigma must lie close together. Because these conditions are hard to meet, most open flowers show only partial autogamy.
The term used for transfer of pollen grains from anthers of one plant to stigma of a different plant which, during pollination, brings genetically different types of pollen grains to stigma, is:
Transfer of pollen grains from anther to stigma of another flower of same plant is known as:
Statement I: Cleistogamous flowers are invariably autogamous. Statement II: Cleistogamy is disadvantageous as there is no chance for cross pollination. Choose the correct answer:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Pollination is the movement of pollen grains from the anther (male part) to the stigma (female part) of a flower. It is needed because the gametes cannot move on their own, so pollen must be carried to the stigma before fertilisation.
Based on the source of pollen: autogamy (pollen reaches the stigma of the same flower), geitonogamy (pollen reaches another flower on the same plant), and xenogamy (pollen reaches a flower on a different plant).
Xenogamy. It is the only type that brings genetically different pollen to the stigma. Geitonogamy looks like cross-pollination but is genetically the same as self-pollination.
Genetically yes. Since both flowers are on the same plant, the pollen is genetically identical, so geitonogamy is genetically equal to autogamy (self-pollination), even though it needs a pollinating agent.
Complete autogamy needs pollen release and stigma receptivity to happen at the same time, and the anthers and stigma must be close together. These conditions are hard to meet in open flowers, so complete autogamy is rare there and is more certain in cleistogamous (closed) flowers.
