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List any three outbreeding… (Class 12 Biology 2026, Q22)

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BiologyCBSE Class 12 · Board exam 2026, set 57/5/1 · 3 marks · Short answer

CBSE Class 12 Biology 2026: question 22

Set in the CBSE Class 12 board exam of 2026, paper 57/5/1, section C, question 22, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q22 · 3 marks · Short answerSexual Reproduction in Flowering Plants

List any three outbreeding devices that flowering plants have developed for cross-pollination and explain how they help to encourage cross-pollination.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 57/5/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Think about the timing, the placement and the genetic compatibility of pollen and stigma in the same flower.

Hint 2

Also consider plants whose flowers are only male or only female.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. Asynchronous maturity: Pollen release and stigma receptivity are not synchronised. Either the pollen is released before the stigma becomes receptive, or the stigma becomes receptive much before pollen release. This prevents self-pollination, so pollen must come from another flower.

    1 mark

  2. Different positions of anther and stigma: The anther and stigma are placed at different positions in the flower. Pollen therefore cannot come in contact with the stigma of the same flower, which favours cross-pollination.

    1 mark

  3. Self-incompatibility: This genetic mechanism prevents pollen from the same flower, or from other flowers of the same plant, from germinating on the stigma or growing a pollen tube in the pistil. Only pollen from another plant can fertilise the ovules. (Production of unisexual flowers, or of male and female flowers on different plants as in papaya, also prevents self-pollination.)

    1 mark

Answer: Asynchronous maturity of pollen and stigma, different positions of anther and stigma, self-incompatibility (also unisexual flowers / dioecy).

Where the marks are

  • Names and explains the first outbreeding device, e.g. non-synchronised pollen release and stigma receptivity (1 mark)
  • Names and explains the second device, e.g. anther and stigma at different positions (1 mark)
  • Names and explains the third device, e.g. self-incompatibility or unisexual flowers / dioecy (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Sexual Reproduction in Flowering Plants, one at a time, marked against the answer key and marking points.Back to the full paper2026 board paper, set 57/5/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.