Question

Describe two phenomena which can prevent both autogamy and geitonogamy and ensure xenogamy

Answer 1

self sterility is
resistance of the stigma to accept the self pollen
herkogamy is and androecium and gynoecium are placed at different levels
this prevent autogamy and geitenogamy and promotes xenogamy

Answer 2

Self-incompatibility and Maturation of female and male reproductive parts at different times.

Explanation:

Autogamy and geitonogamy is self-fertilization. In autogamy, the pollen grain produced by a flower stamen fertilizes the egg of the same flower. In geitonogamy, the pollen of one flower is transferred to the stigma of a different flowers of the same plant.

So to prevent self-fertilization plants use many strategies like self-incompatibility in which stigma do not accept the pollen grain of same flower and the second method is difference in maturation time of stamen and pistil.

Learn more about xenogamy:

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