The flowers which open after pollination is

The flowers which open after pollination are Chasmogamy.
Chasmogamy is a plant reproductive mechanism in which pollination occurs in chasmogamous flowers.
These flowers are commonly showy with open petals encircling exposed reproductive parts. Chasmogamous stems from Greek for "open marriage", named after the open arrangement of floral structures.
Seeds produced by chasmogamous flowers that are cross-pollinated, may also exhibit hybrid vigour (heterosis) and increased fitness.