Choose the correct statement from the following.

The correct answer is Option (2) → Cleistogamous flowers exclusively demonstrate autogamy.

Plants such as Viola, Oxalis and Commelina produce two types of flowers. Chasmogamous flowers open and expose their anthers and stigma like other flowers. Cleistogamous flowers do not open at all; their anthers dehisce inside the bud, and the pollen reaches the stigma of the same flower.

Option (1) Chasmogamous flowers exclusively demonstrate geitonogamy. — Incorrect. Chasmogamous flowers are open flowers, so their pollen can reach the same flower, another flower of the plant or another plant. They are not limited to geitonogamy.

Option (2) Cleistogamous flowers exclusively demonstrate autogamy. — Correct. Cleistogamous flowers are invariably autogamous, as there is no chance of cross-pollen landing on the stigma.

Option (3) Cleistogamous flowers can exhibit both autogamy and geitonogamy. — Incorrect. Geitonogamy needs pollen to travel to another flower of the same plant. A cleistogamous flower never opens, so this cannot happen.

Option (4) Chasmogamous flowers never exhibit autogamy. — Incorrect. Complete autogamy is rare in open flowers, but it can occur when pollen release and stigma receptivity are in step and the anthers and stigma lie close together.

NCERT Extract:
Pollination – “… Some plants such as Viola (common pansy), Oxalis, and Commelina produce two types of flowers – chasmogamous flowers which are similar to flowers of other species with exposed anthers and stigma, and cleistogamous flowers which do not open at all (Figure 1.9c). In such flowers, the anthers and stigma lie close to each other. When anthers dehisce in the flower buds, pollen grains come in contact with the stigma to effect pollination. Thus, cleistogamous flowers are invariably autogamous as there is no chance of cross-pollen landing on the stigma.”