List three strategies that a bisexual chasmogamous flower can evolve to prevent self pollination (autogamy).

Explanation

The three strategies that a bisexual chasmogamous flower can prevent self pollination are
1. Dichogamy: Androecium and gnoecium of a bisexual flower mature at different times. This mechanism promote cross pollination by preventing self pollination in bisexual flowers. It is of 2 types.
a. protandry: Androecium matures earlier than gynoecium. The entire pollen fall off fromt eh stamens, by the time gynoecium matures eg: Helianthus, Gossypium.
b. Protogyny: Gynoecium matures earlier than androecium.
Thus by the time the gynoecium matures, the stamens remain in immagure condition.
E.g: Solanum, Scrophularia.

2. Herkogamy: The arrangement of male and female reproductive organs at different levels in a bisexual flower. Tis contrivancy prevents self pollination, thugh both the reproductive organs mature at the same time.
Eg: a. Stigmas project beyond stamens in Gloriosa superba.
3. Self sterilty: Insome bisexual flowers, the pollen grains fail to germinate on the stigma of the same flower. But the same pollen grains germinate, when they fall on the stigma of other flower of the same species.
e.g: Abutilon, Passiflora