• To avoid 'breeding depression' hermaphrodite angiosperms develop outbreeding devices.
• In some species, the pollen is released before the stigma becomes receptive or stigma becomes receptive much before the release of pollen.
• In some species, the stigma and anther are placed at different locations so that the pollen grain prevents contact with the stigma of the same flower.
• Both of these devices prevent autogamy.
• The third device to avoid inbreeding is self-incompatibility. It is a genetic mechanism that prevents self-pollen from fertilizing the ovules by inhibiting pollen germination.
• Eg. Castor, maize.
Another device for preventing self-pollination is the production of unisexual flowers is the production of unisexual flowers
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