Pollination and fertilization in an unopened flower bud is the situation called

Pollination and fertilization in an unopened flower bud is a situation called Cleistogamy.
Cleistogamy is a type of automatic self-pollination of certain plants that can propagate by using non-opening, self-pollinating flowers.
The principal advantage of cleistogamy is that it requires fewer plant resources to produce seeds than chasmogamy because the development of petals, nectar, and large amounts of pollen is not required.