Identify the conditions which prevent autogamy :
(A) Presence of male or female flowers on different plants
(B) Self incompatibility
(C) Unsynchronised pollen release and stigma receptivity
(D) Geitonogamy
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A), (B) and (C) only
(A) Presence of male or female flowers on different plants — True. Unisexual flowers on separate plants prevent both autogamy and geitonogamy.
(B) Self incompatibility — True. Pollen of the same flower cannot fertilise the ovules.
(C) Unsynchronised pollen release and stigma receptivity — True.
(D) Geitonogamy — False. Geitonogamy is pollination between flowers of the same plant; it is not a device.
NCERT Extract:
Pollination – “… Flowering plants have developed many devices to discourage self-pollination and to encourage cross-pollination. In some species, pollen release and stigma receptivity are not synchronised. Either the pollen is released before the stigma becomes receptive or stigma becomes receptive much before the release of pollen. In some other species, the anther and stigma are placed at different positions so that the pollen cannot come in contact with the stigma of the same flower. Both these devices prevent autogamy. The third device to prevent inbreeding is self-incompatibility. This is a genetic mechanism and prevents self-pollen (from the same flower or other flowers of the same plant) from fertilising the ovules by inhibiting pollen germination or pollen tube growth in the pistil. Another device to prevent self-pollination is the production of unisexual flowers.”