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

Autogamy is pollination where pollination is achieved within the same flower, i.e., it is type of self pollination. In this the pollens are transferred from anther to stigma of same flower.

Chasmogamous flower are flowers with exposed anthers and stigma.

The strategies that a bisexual chasmogamous flower can evolve to prevent self-pollination are:

i. As pollen release and stigma reception should be synchronised for autogamy to take place. Avoiding synchronisation of pollen release and stigma reception can prevent autogamy that is avoiding the simultaneous maturing of anther and stigma. Such type of pollination is known as Dichogamy where stigma and anther matures at different time. Examples of such type of flowers are Sunflower, Datura, Solamium, etc.

ii. Self-incompatibility or self-sterility is a genetic mechanism that prevents self-pollination (i.e., pollination from same flower or other flowers of same plant) from fertilizing the ovules by inhibiting pollen germination or pollen tube growth in the pistil.

iii. In chasmogamous flower length of anther and stigma plays a secondary role in autogamy. Therefore by placing anther and stigma at different position, in such a way that the pollen of a flower doesn’t come in contact with stigma of the same flower can prevent autogamy.