Question

Which is the character of a castor plant to avoid autogamy?
A. Unisexuality
B. Porogamy
C. Protandry
D. Heterostyly

Answer 1

Hint:The transferral of pollen grains from the open anther of the stamen to the receptive stigma of the carpel is called pollination. It is of two types self-pollination and cross-pollination. Self-pollination involves the transfer of pollen grains from the anther of a flower to the stigma of the same flower or genetically similar flower.

Complete answer: Self-pollination is of two types autogamy and geitonogamy
1. Autogamy: a kind of pollination in which the pollen from the anthers of a flower is transferred to the stigma of the same flower. To avoid autogamy many methods are developed by the plant.
2. Geitonogamy. It is a kind of pollination in which the pollen from the anthers of one flower is transferred to the stigma of another flower borne on the same plant.
Devices for xenogamy:
flowers are unisexual and the plants are dioecious i.e, male and female flowers are present on different plants. (if the pants are monoecious, it avoids only autogamy but not geitonogamy).
Castor plants are monoecious i.e. male and female are present in different flowers.

So the correct answer is option is A. Unisexuality.

Note:Other devices of xenogamy are pollen release and stigma receptivity are not synchronized i.e. either the anthers mature and release pollen grains much before the stigma is receptive (protandry) or the stigma becomes receptive much before the pollen grains of the same flower mature (protogyny). The anthers and the stigma of a flower are placed in such a way that the pollen from the anthers cannot fall on the stigma. Self-incompatibility is a genetic mechanism that prevents the germination of pollen grains on the stigma of the same flower. Heterostyly is the flowers of some plants that have different lengths of stamens and styles so that self-pollination is not possible.