Question

1) some plants have assured seed set explain why and also define xenogamy​

Answer 1

Explanation:

Cleistogamy is the phenomenon, where flowers never open and in such flowers, only self-pollination occurs within the bud (unopened flower). Bisexual flowers which do not open at all are called cleistogamous. In such flowers, anthers and stigma lie close to each other. When the anthers dehisce in the flower buds, pollen grains come in contact with the stigma and pollination occurs. Cleistogamous flowers are not dependent on external agencies for pollination. Hence, seed setting is not dependent on pollinators.

Hence, assured seed set is possible even in the absence of pollinators when the flower is Cleistogamous.