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What are the possible types of pollinations in chasmogamous flowers? Give reasons.

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Chasmogamous flowers are open flowers in which stigma and anthers are exposed, and flowers are similar to other species. Possible types of pollinations in chasmogamous flowers are as follows:

  1. Geitonogamy: The situation in which pollen grains from the same plant but different flower reaches the stigma is called geitonogamy. This is similar to autogamy because the zygote gets the gene pool from the same plant.
  2. Xenogamy: The situation in which the pollen grains from a different plant reaches the stigma is called xenogamy. This can be termed as the true cross-pollination because the zygote gets the gene pool from 2 different plants.

Most of the plants produce hermaphrodite flowers, and thus, self-pollination is a clear cut eventuality. However, continuous self-pollination can result in inbreeding depression. The variation will not be possible in case of self-pollination. Hence, plants have evolved in various ways and means to facilitate cross-pollination even in dioecious flowers. One of the strategies followed by plants is a loss of synchronization between pollen release and stigma maturity. Another strategy is self-incompatibility between pollens and the stigma of the same flower.

A third strategy is a positional difference between anthers and stigma so that pollens from the same flower are unable to reach the stigma.

 

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