Question

The process of pollen transfer from the anther to the stigma of same flower before anthesis is called-

• A. Xenogamy
• B. Allogamy
• C. Geitonogamy
• D. Cleistogamy

Hint:

- Cleistogamy: Closed flowers, guaranteed self-pollination before/without anthesis.
- Geitonogamy: Between different flowers of the same plant.
- Xenogamy Allogamy: Between flowers on different plants (cross-pollination).

Answer 1

The Correct Option is D

Concept:
Flowering plants exhibit diverse floral adaptations and pollination mechanisms that promote either self-pollination (autogamy) or cross-pollination (allogamy).
Anthesis refers to the natural opening of the floral bud to expose its reproductive organs (stigma and anthers) to external pollinating vectors.
Certain floral mechanisms ensure complete self-fertilization by completing pollen shed and receptive pollination entirely within closed buds or prior to anthesis.

Step 1: Defining Cleistogamy and Chasmogamy:
- Cleistogamy: The phenomenon in which flowers never open at all, or in which self-pollination takes place inside the closed bud prior to anthesis. The anthers dehisce and shed viable pollen directly onto the receptive stigma of the same closed flower (e.g., in Commelina, wheat, and groundnut).
- Chasmogamy: The condition in which flowers open fully at maturity, exposing stigmas and stamens to external pollinators.

Step 2: Evaluating Alternative Pollination Types:
- Xenogamy Allogamy: True cross-pollination where pollen grains are transferred from the anther of one flower to the stigma of a genetically distinct flower on a different plant.
- Geitonogamy: Pollen transfer between different flowers situated on the same plant; genetically equivalent to autogamy but ecologically requiring a pollinator.

Step 3: Synthesis:
The transfer of pollen from the anther to the stigma within the same flower before floral opening (anthesis) is a defining characteristic of cleistogamy (and bud pollination).

Step 4: Final Answer:
Therefore, the described process is Cleistogamy, corresponding to option (D).