Pollination:-

• It is the transfer of pollen grains from the anther to the stigma of a pistil.
• Some external agents help the plants with pollination.
  Depending on the source of pollen, pollination is 3 types.

a. Autogamy:

• In this, pollen grains transfer from the anther to the stigma of the same flower.
• Complete autogamy is rare in flowers with exposed anthers and stigma.
• Autogamy in such flowers requires synchrony in pollen release and stigma receptivity. Also, the anthers and stigma should lie close to each other to enable self-pollination.
• Plants like Viola (common pansy), Oxalis, & Commelina produce 2 types of flowers:
• 1. Chasmogamous flowers: They are similar to flowers of other species with exposed anthers and stigma.
• 2. Cleistogamous flowers: They do not open at all. Anthers & stigma lie close to each other.
• They are autogamous as there is no chance of cross-pollination.
• When anthers dehisce in the flower buds, pollen grains come in contact with the stigma for pollination.
• Cleistogamous flowers produce assured seed-set even in the absence of pollinators.

b. Geitonogamy:

• In this, pollen grains are transferred from the anther to the stigma of another flower of the same plant. It is a functionally cross-pollination involving a pollinating agent. But it is genetically similar to autogamy since the pollen grains come from the same plant.

c. Xenogamy:

• In this, pollen grains transfer from the anther to the stigma of a different plant. This brings genetically different types of pollen grains to the stigma.