Question

What are chasmogamous flowers? Can cross-pollination occur in cleistogamous flowers? Give reasons for your answer.

Answer 1

Hint: Chasmogamous and cleistogamous flowers, both show autogamy (pollination between the same flower i.e. stigma and anther of the same flower).

Complete answer:
Chasmogamous flowers are open flowers having exposed anthers and stigma. Chasmogamous flowers open at maturity. These flowers facilitate cross-pollination (and sometimes cross-pollination) and are dependent on pollinating agents. In these flowers, reproductive structures are often larger, and thus more pollen needs to be produced. These flowers are showy and highly conspicuous. These flowers are usually dichogamous.
On the other hand, cleistogamous flowers are closed flowers that do not open and remain in the bud state. The anthers and stigmas are not exposed in this type and lie close to each other. The reproductive structures are often smaller thus less pollen needs to be produced.
Cross-pollination cannot occur in cleistogamous flowers because they never open. Hence, only self-pollination is possible in these flowers. When anther dehisces in the flower the pollen grain comes in close contact with the stigma to affect self-pollination, thus there is no chance of cross-pollination and only self-pollination occurs. These flowers are non-showy and inconspicuous and homogamous.

Additional Information: Example. Viola (common pansy), Oxalis, and Commelina produce chasmogamous and cleistogamous flowers.

Note: - Cleistogamous flowers are invariably autogamous.
- Seed production is pre ensured in cleistogamous flowers due to absence of pollinators.
- Synchrony in pollen grain release and stigma receptivity are the two factors ensuring self-pollination.