8. Mention two strategies evolved to prevent self-pollination in flowers.

Answers (1)
S Sonika

Self-pollination refers to the transfer of pollen grains from the anther of a flower to the stigma of the same flower. Continuous self-pollination can reduce the variations in the progeny and cause a reduction in the vigour and vitality. Thus, plants have developed certain mechanisms to avoid self-pollination and ensure cross-pollination. The two of these mechanisms to prevent self-pollination are as follows:

1. Self sterility or self-incompatibility - In this mechanism, the pollen grains of a flower do not germinate on the stigma of the same flower. This occurs due to the presence of some self-sterile genes. This mechanism is genetic.

2. Dichogamy- In this method, the timing of maturation of anthers and stigmas of a bisexual flower is different so as to prevent self-pollination. 

Protandry- Anthers mature earlier than the stigma of the same flower. So, even if the pollens fall on these stigmas, they are unable to germinate. E.g. sunflower, Salvia.

Protogyny- Stigmas mature earlier than anthers and get pollinated by mature pollen grains of other flowers. E.g. Mirabilis jalapa.

 

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