Which type of pollination brings genetically different types of pollen grains to the stigma?

Xenogamy

The correct answer is c) Xenogamy.

There are three types of pollination described: autogamy, geitonogamy, and xenogamy.

1. Autogamy: Autogamy refers to the transfer of pollen grains from the anther to the stigma of the same flower. It occurs within a single flower, and genetically, it involves the self-pollination of the plant. In autogamy, the pollen grains and stigma of the same flower come into contact, leading to fertilization with genetically identical pollen.
2. Geitonogamy: Geitonogamy involves the transfer of pollen grains from the anther to the stigma of another flower of the same plant. While functionally it is a form of cross-pollination since it involves a pollinating agent, genetically it is similar to autogamy because the pollen grains come from the same plant. Geitonogamy does not introduce genetically different pollen to the stigma.
3. Xenogamy: Xenogamy is the type of pollination that brings genetically different types of pollen grains to the stigma. It involves the transfer of pollen grains from the anther to the stigma of a different plant. This is the only form of pollination that introduces genetically diverse pollen to the stigma, which promotes cross-fertilization and genetic variation within plant populations.

Xenogamy is an important mechanism for promoting genetic diversity in flowering plants. It allows for the exchange of genetic material between different individuals, which can enhance the adaptability and survival of the species. Biotic agents such as insects, birds, or mammals are often involved in facilitating xenogamy by carrying pollen from one plant to another.

Overall, xenogamy plays a crucial role in maintaining genetic diversity within plant populations and is an essential factor in plant evolution and adaptation to changing environments.