Name three contrivances by which plants avoid self-pollination.

Unisexuality, where a flower or a plant bears only one sex. Dichogamy, where the anthers and the stigma of the same flower mature at different times. Self-sterility, where the pollen of a flower cannot germinate on its own stigma. Heterostyly, with styles and stamens of different lengths, is a fourth.

No citable source has been recorded for this record. Treat it as practice material, not as fact.

Explanation

All of them favour cross-pollination and so promote variation.