Question

Unisexuality of flowers prevents:
A. Geitonogamy but not xenogamy
B. Autogamy and geitonogamy
C. Autogamy but not geitonogamy
D. Both geitonogamy and xenogamy

Answer 1

Hint: A unisexual flower consists of three whorls that include petals, sepals, the male reproductive structure (stamen), or the female reproductive structure (pistil). Male and female gametes are inferred from the same individual in self-fertilization. The self-pollination of the anther and stigma of the same flower is regarded as autogamy.


Step by step solution:
Autogamy is a type of pollination in which pollen grains are transferred from the anther to the stigma of a plant's same flower. Only bisexual flowers with both male and female reproductive parts can undergo this type of pollination.
Autogamy would be prevented by unisexuality which is the presence of either male or female reproductive parts in a flower.
Geitonogamy is a type of pollination in which pollen grains are transferred from the anther to the stigma of another flower on the same plant. This is possible in monoecious plants with both male and female unisexual flowers, but not in dioecious plants.
As a result, unisexuality does not completely rule out the possibility of geitonogamy.
Xenogamy is a type of pollination in which pollen from one flower is transferred to another flower of a different plant. This can occur in plants with unisexual or bisexual flowers.
Pollen from a male flower can always be transmitted to the stigma of another female flower on a different plant of the same species, so unisexuality doesn't really rule out xenogamy.
Hence, The correct option is C.

Note: Unisexuality encourages or promotes cross-pollination, xenogamy, and discourages self-pollination, i.e. autogamy. Since geitonogamy involves the transfer of pollen grains between two flowers of the same plant, unisexuality does not preclude geitonogamy.