The two strategies evolved to prevent self-pollination in flowers are –

• Dichogamy – Maturation of anther and stigma of a flower at different times to prevent self-pollination.

When anther matures before stigma, it is called protandry.

When stigma matures before anther, it is called protogyny.

• Self-incompatibility – In some flowers, self-sterile genes are present due to which the pollen grains do not germinate on the stigma of that flower. E.g. potato, tobacco.