Question

Among the situations given below, choose the one that prevents both autogamy and geitonogamy.

• A. Monoecious plant bearing unisexual flowers
• B. Dioecious plant with bisexual flowers
• C. Monoecious plant with bisexual flowers
• D. Dioecious plant bearing only male or female flowers

Hint:

Monoecious plants prevent autogamy but allow geitonogamy. Dioecious plants prevent both autogamy and geitonogamy, ensuring cross-pollination.

Answer 1

The Correct Option is D

Concept: Pollination may occur in three ways:
• Autogamy – transfer of pollen to the stigma of the same flower.
• Geitonogamy – transfer of pollen between different flowers of the same plant.
• Xenogamy – transfer of pollen between flowers of different plants. A dioecious plant bears male and female flowers on separate individuals.

Step 1: Understand autogamy. Autogamy requires a bisexual flower possessing both stamens and carpels. Unisexual flowers cannot undergo autogamy.

Step 2: Understand geitonogamy. Geitonogamy requires male and female flowers to be present on the same plant. This is possible in monoecious plants.

Step 3: Analyze dioecious plants. In dioecious plants:
• One plant bears only male flowers.
• Another plant bears only female flowers. Therefore:
• Autogamy is impossible.
• Geitonogamy is impossible. Only xenogamy can occur.

Step 4: Final conclusion. The condition that prevents both autogamy and geitonogamy is: \[ \text{Dioecious plant bearing only male or female flowers} \] Hence option (D) is correct.