What is an advantage of cleistogamy?

The correct answer is Option (3) → Independence from pollinators

Some plants, such as Viola, Oxalis and Commelina, have flowers that never open. These are cleistogamous flowers. Their anthers and stigma lie close together inside the closed flower, so the pollen falls on the stigma of the same flower. Such flowers are always self-pollinated (autogamous).

Option (1) Increased genetic variability — Incorrect. Cleistogamous flowers are always self-pollinated, and no outside pollen can reach the stigma. So they give less genetic variation, not more.

Option (2) Ability to undergo vivipary — Incorrect. Vivipary is unrelated: it is the germination of seeds while still on the parent plant. It is not linked to closed flowers or to the way pollination happens.

Option (3) Independence from pollinators — Correct. The flower is closed and pollinates itself, so it does not need wind, water or insects. Cleistogamous flowers therefore give assured seed-set even in the absence of pollinators.

Option (4) More vigorous offspring — Incorrect. Continued self-pollination leads to inbreeding depression, which gives weaker offspring. More vigorous offspring come from cross-pollination, not from cleistogamy.

NCERT Extract:
Kinds of 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). … Thus, cleistogamous flowers are invariably autogamous as there is no chance of cross-pollen landing on the stigma. Cleistogamous flowers produce assured seed-set even in the absence of pollinators.”