Question

What conditions make flowers invariably autogamous?

Answer 1

Autogamous is a type of fertilisation called self fertilisation. It involves fusion of two gametes that come from the same individual. It is mainly found in unicellular organisms like protists.

Complete answer:
Autogamy is possible when anther and stigma are closely present together and there is synchrony in the release of pollen and stigma receptivity.

Autogamy is further divided into two types:
(i) Cleistogamy: Some plants never open up and the dehiscence of anther takes place inside closed flowers for pollination. It is strictly autogamous as there is no chance of cross pollination. Eg are Oxalis , Viola , etc.
(ii) Homogamy: In some plants like Mirabilis , both the anthers and stigma mature at the same time.

Autogamy is possible only when the flower remain closed at every time and the flower must be bisexual. It is also possible when the anther and the stigma matures at the same time. For autogamy the plants must be bisexual.

Note:
Self pollination maintains purity of species and the plants do not depend upon pollinating agents. There is no need for production of a large number of pollen grains.