Q28. 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) Ge

Question

Q28. 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:
(a) (A), (B) and (D) only
(b) (A), (B) and (C) only
(c) (A), (B), (C) and (D) only
(d) (B), (C) and (D) only

FirstInTest · Accepted Answer

Correct answer: b. Autogamy is a type of self-pollination where pollen is transferred from the anther to the stigma of the same flower. To promote cross-pollination and genetic diversity, many plants have evolved outbreeding devices that prevent autogamy:
*   **(A) Presence of male or female flowers on different plants (Dioecy):** In dioecious plants (e.g., papaya), male and female flowers are on separate plants. This entirely prevents pollen from one flower pollinating any other flower on the same plant, thus preventing both autogamy and geitonogamy. This statement prevents autogamy.
*   **(B) Self-incompatibility:** This is a genetic mechanism that prevents self-pollen (pollen from the same plant) from fertilizing the ovules, either by inhibiting pollen germination on the stigma or by preventing pollen tube growth. This statement prevents autogamy.
*   **(C) Unsynchronised pollen release and stigma receptivity (Dichogamy):** If the pollen is released at a different time than when the stigma becomes receptive in the same flower, self-pollination (autogamy) is avoided. This statement prevents autogamy.
*   **(D) Geitonogamy:** This is a form of self-pollination involving the transfer of pollen from the anther of one flower to the stigma of another flower on the *same plant*. While it requires a pollinator, it is genetically equivalent to autogamy as the pollen comes from the same genetic individual. Therefore, geitonogamy does *not* prevent autogamy; it is a type of self-pollination.
Thus, conditions (A), (B), and (C) prevent autogamy.

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