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One of the major approaches… (Class 12 Biology 2023, Q25)

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BiologyCBSE Class 12 · Board exam 2023, set 57/5/1 · 3 marks · Short answer

CBSE Class 12 Biology 2023: question 25

Set in the CBSE Class 12 board exam of 2023, paper 57/5/1, section C, question 25, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q25 · 3 marks · Short answerSexual Reproduction in Flowering Plants

One of the major approaches of crop improvement programme is Artificial Hybridisation. Explain the steps involved in making sure that only the desired pollen grain pollinate the stigma of a bisexual flower by a plant breeder.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 57/5/1.

Hints

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

Hint 1

A bisexual flower can pollinate itself, so first remove the part that makes pollen.

Hint 2

Then think about how to keep stray pollen out until the chosen pollen is applied.

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. Emasculation: the anthers are removed from the flower bud with forceps before they dehisce. This prevents self-pollination of the bisexual flower.

    1 mark

  2. Bagging: the emasculated flower is covered with a bag of suitable size, usually butter paper. This protects its stigma from contamination by unwanted pollen.

    1 mark

  3. Dusting and rebagging: when the stigma becomes receptive, mature pollen collected from the desired male parent is dusted on it. The flower is then rebagged and left to develop fruit.

    1 mark

Answer: Emasculation (remove anthers before dehiscence), bagging (cover the flower to prevent foreign pollen), then dusting desired pollen on the receptive stigma and rebagging.

Where the marks are

  • Emasculation explained: removing anthers before dehiscence (1 mark)
  • Bagging explained: covering the flower to prevent unwanted pollen (1 mark)
  • Dusting desired pollen on the stigma and rebagging (1 mark)
  • Only ½ mark each if emasculation and bagging are merely named

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 paper2023 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.