Question

24. Chasmogamous flowers remain open and expose their reproductive parts.

Explain how this structural feature supports different types of pollination.

Hint:

Open flowers with exposed anthers and stigma allow autogamy, geitonogamy and xenogamy.

Answer 1

Step 1: Recall what chasmogamous flowers are:
Chasmogamous flowers are flowers with exposed anthers and stigma, like most flowers we see.
They open at maturity, so their reproductive parts can be reached from outside.

Step 2: Support for autogamy (self-pollination):
In many chasmogamous flowers the anthers and stigma lie close together at the same level.
Pollen shed from the anther can fall on the stigma of the same flower.
This transfer within one flower is called autogamy.

Step 3: Support for geitonogamy:
Pollen can also be carried by wind or an insect from one flower to another flower of the same plant.
The open flower allows this, and genetically it is similar to self-pollination, though it needs an agent.

Step 4: Support for xenogamy (cross-pollination):
Open flowers show colour, scent and nectar, so insects visit them. Wind and water can also reach the exposed parts.
The agent carries pollen from the anther of one plant to the stigma of a different plant.
This xenogamy is the only type that brings in new genetic variation.

Final Answer:
Because the anthers and stigma are exposed, the flower allows autogamy, geitonogamy and xenogamy (cross-pollination) through wind, water, insects or contact.