Cleistogamy refers to the pollination of cleistogamous flowers. Cleistogamous flowers do not open at all and therefore show self-fertilisation or autogamy. They do not depend on pollinating agents for pollination.
Autogamy is a type of self-pollination, wherein pollination occurs within the same flower. Cleistogamous flowers are exclusively autogamous. There are certain characteristics that are necessary for autogamy:
- Synchronisation in pollen release and stigma receptivity.
- Close proximity between anthers and the stigma.
- Complete autogamy is not possible in flowers with exposed male and female reproductive parts.
Cleistogamous flowers produce an assured seed-set as the pollination is not dependent on any external agent. Examples of plants showing cleistogamy are peas, peanuts, etc. Some plants produce both chasmogamous and cleistogamous flowers, e.g. Commelina, Viola, Oxalis, etc.
Cleistogamy refers to “closed marriage” and chasmogamy means “open marriage”. Cleistogamous flowers are the opposite of chasmogamous flowers, which open and expose their reproductive parts to allow cross-pollination.
Flowers with exposed anthers and stigma are referred to as chasmogamous flowers. Most chasmogamous flowers are cross-pollinated by various pollinating agents such as wind, bees, insects, etc. Chasmogamous flowers show both autogamy and allogamy. Cross-pollination in chasmogamous flowers is beneficial as it leads to more genetic diversity.
Advantages of Cleistogamy
Some advantages of cleistogamy are:
- Cleistogamous flowers are self-pollinated, therefore they do not depend on pollinators for pollination.
- It helps in producing an assured seed-set even in adverse conditions.
- Synthesis of large amounts of pollen, nectar and attractive petals are also not required.
- It helps in maintaining the population of plants even in unfavourable conditions.
There are some disadvantages also of self-fertilisation. It reduces genetic diversity and leads to inbreeding depression.
Most plants producing cleistogamous flowers also produce chasmogamous flowers. The presence of both types of flowers allows both self-fertilisation and cross-fertilisation. It ensures less dependency on pollinators and environmental conditions and results in reproductive success along with genetic diversity.
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