If the plants have either male or the female flowers on it , then it prevents

Options

A. autogamy, but not geitonogamy
B. both geitonogamy and xenogamy
C. geitonogamy, but not xenogamy
D. autogamy and geitonogamy

Answer

A

Explanation

Unisexuality of flowers prevents autogamy, but not geitonogamy. Autogamy also called self-pollination involves the transfer of pollen grains of one flower to the stigma of same flower. Self-pollination occurs only in bisexual or hermaphrodite flowers.
Geitonogamy involves the transfer of pollen grains from a male flower to stigma of female flower of same plant. Thus, geitonogamy operates only in monoecious plants, i.e. plants having male and female flowers on different places.
Allogamy or xenogamy also known as cross-pollination involves the transfer of pollen grains of male flower to the stigma of genetically different female flower. It takes place via various agencies like wind, water, insects, etc.