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

Explanation

A) Dichogamy: "Pollen release and stigma receptivity are not synchronised". In sunflower, the pollen is released before the stigma becomes receptive (protandry). In Datura, Solanum, the stigma becomes receptive much before the release of pollen (Protogyny) leads to cross pollination.
B) Herkogamy : The Male (anther) and female (stigma) sex organs are placed at different positions (Hibiscus) or in different directions (Gloriosa), called Herkogamy. In these plants, the pollen can not come in contact with the stigma of the same flower leads to cross pollination.
C) Self-sterility : It is a genetic mechanism which prevents the self pollen frorn fertilising the ovules by inhibiting pollen germination or pollen tube growth in the pistil.
E.g.: Abutilon.