Advantage of cleistogamy is

Cleistogamous flowers do not open at all. 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. Cleistogamous flowers produce assured seed-set even in the absence of pollinators.

Cleistogamy involves self-pollination which leads to less genetic variability.

Self- pollination in cleistogamy creates more homozygosity but vigorous nature of offspring depends on heterozygosity.

Vivipary means germination of seed inside the fruit when it is still attached to the parent plant