Question

Papaya plant exhibit xenogamy only. Why?

Answer 1

In same plant pollen grains are fall in stigma but fertilization not occur due to sterility of male organs so in this cases they require cross pollination.
so papaya exhibit xenogamy

Answer 2

In normal scenario, male and female part of a plant present on a same plant but in case of papaya, male and female reproductive organs (flowers) are present on two different plants which is why papaya plant has to exhibit xenogamy.

Xenogamy is defined as, fertilization of a flower with pollen grains from a genetically different plant (flower).