Question

In castor and maize plants,
a. Autogamy is prevented but not geitonogamy
b. Both autogamy and geitonogamy are prevented
c. Male and female flowers are borne by different plants
d. The anthers and stigma are placed at different positions to encourage cross-pollination.

Answer 1

When a plant has male and female flowers separately on the same plant, it is referred to as unisexual. Castor and maize have unisexual flowers. Hence we can conclude that autogamy is not possible in castor and maize because autogamy is a type of pollination which is achieved within the same flower.

Complete answer:
• The presence of separate flowers prevents autogamy.
• However, the chances of geitonogamy are induced by the fact that castor and maize have separate flowers on the same plant.
• The word Geitonogamy has come from the Greek word geiton meaning neighbour and gamos meaning marriage.
• Geitonogamy is the process of transferring pollen grains of one flower to the stigma of another flower belonging to the same plant.
• It is a form of self-pollination.

Hence, the correct answer is option (A).

Additional information:
• Pollination is two types, they are self-pollination and cross-pollination.
• Self-pollination is of two types- Autogamy and Geitonogamy.
• Autogamy can be performed by three methods-homogamy, cleistogamy, and bud pollination.
• Cross-pollination or xenogamy is the transfer of pollen grains from the anther of one flower to the stigma of a genetically different flower.
• Wind pollination, water pollination, insect pollination, bird pollination, bat pollination, snail pollination are the different types of cross-pollination.

Note: Castor reproduces by geitonogamy and can sometimes perform wind-pollination or insect-pollination. Apart from geitonogamy, maize performs pollination by the wind too. When the number of flowers is small or they are scattered ant closely spaced, self-pollination can be an advantage.