What are the possible types of pollinations in chasmogamous flowers? Give reasons.

Chasmogamous flower are flowers with exposed anthers and stigma.

All the following types of pollinations are possible in chasmogamous flowers are:

i. Autogamy or self-pollination - for autogamy to occur in chasmogamous flower both pollen and ovules should mature simultaneously. As pollen release and stigma reception should be synchronised for autogamy to take place.

ii. Dichogamy - For this type of pollination synchronisation of pollen release and stigma reception should be avoided that is by avoiding the simultaneous maturing of anther and stigma. In this type of pollination stigma and anther matures at different time. Examples of such type of flowers are Sunflower, Datura, Solamium, etc.

iii. 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.

iv. 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.

v. Geitonogamy – here pollen and pistil mature at different times but are self – compatible.

vi. Xenogamy – here pollen grains from the flower of one plant to the stigma of another plant. This pollination brings genetically different types of pollen grains.