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Sexual Reproduction in Flowering Plants — BIOLOGY STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceBIOLOGYSexual Reproduction in Flowering Plants1 Mark
Question
For two statements are given-one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both assertion and reason are true, and reason is the correct explanation of assertion.
  2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
  3. Assertion is true, but reason is false.
  4. Both assertion and reason are false.
Assertion: Self-sterility inhibits self-pollination.
Reason: Dichogamy is the condition in which only self-pollination occurs.
✓

Answer

  1. Assertion is true, but reason is false.

​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Explanation:

Self-sterility is the condition in which the pollen of a flower has no fertilizing effect on the stigma of the same flower. Cross-pollination is thus the only method in them for the production of seeds. In many bisexual flowers, the anther and stigma often mature at different times. This condition is known as dichogamy. Dichogamy often stands as a barrier to self-pollination. There are two conditions of dichogamy.

  1. Protogyny when the gynoecium matures earlier than the anthers of the same flowers.
  2. Protandry when the anthers mature earlier than the stigma of the same flower. In both cases, only cross pollination is possible.

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