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Read the following passage… (Class 10 Science 2026, Q15b)

questionbuddy.in/q/cbse-10-science-2026-31-3-1-q15b-not-plants-carry-out-photosynthesis

ScienceCBSE Class 10 · Board exam 2026, set 31/3/1 · 4 marks · Case-based

CBSE Class 10 Science 2026: question 15(b)

Set in the CBSE Class 10 board exam of 2026, paper 31/3/1, section A, question 15(b), for 4 marks. Try it first; the hints and our step-by-step solution are below.

Q15(b) · 4 marks · Case-basedCompetency-basedLife Processes

Read the following passage and answer the questions that follow :

Not all plants carry out photosynthesis by the same mechanism. In most plants, it depends directly on gaseous carbon dioxide that diffuses into the leaf. However, some plants can store carbon dioxide in the vacuole of the leaf cells as part of a complex carbon compound. This compound is transported to the chloroplast and releases carbon dioxide when required for photosynthesis. This special mechanism is believed to have evolved as an adaptation in such plants which do not open stomata during the daytime to conserve water for survival in dry conditions (desert conditions).

  1. (i)

    List the events that occur during the process of photosynthesis.

    0 marks
  2. (ii)

    When are such desert plants likely to take in carbon dioxide from the environment, unlike other plants ?

    0 marks
  3. (iii)

    Draw a labelled diagram of stomata with open stomatal pore.

    0 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 31/3/1.

Hints

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

Hint 1

Photosynthesis has three steps: capture light, use the light energy, and fix CO₂.

Hint 2

If stomata stay closed in the day, when must they open? For the diagram, remember that guard cells bulge when the pore is open.

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. (i) The events in photosynthesis are: (1) chlorophyll absorbs light energy; (2) light energy is converted into chemical energy, and water molecules are split into hydrogen and oxygen; (3) carbon dioxide is reduced to carbohydrates.

    1 mark

  2. (ii) Such desert plants take in at night, when their stomata open. They store it as an intermediate compound and use it during the day.

    1 mark

  3. (iii) Diagram: draw a pair of kidney-shaped guard cells facing each other with a pore between them, inside an outline of the leaf epidermis. The guard cells should be bulging (turgid) so the gap between them is wide open.

    1 mark

  4. Labels: Guard cells, Stomatal pore (open), Chloroplast (inside the guard cells), Nucleus, Epidermal cells / cell wall.

    1 mark

Answer: (i) Light absorption by chlorophyll; conversion of light to chemical energy with splitting of water; reduction of CO₂ to carbohydrates. (ii) At night. (iii) Labelled diagram of an open stoma.

Where the marks are

  • Lists the three events of photosynthesis (1 mark)
  • States that CO₂ is taken in at night (1 mark)
  • Correct diagram of a stoma with an open pore (1 mark)
  • Correct labels: guard cells, stomatal pore, chloroplast, nucleus (1 mark)

Revise the chapter

  • Chapter: Life Processes (notes, formulas, where marks are lost and every past question)
Practise this chapterBoard-style questions from Life Processes, one at a time, marked against the answer key and marking points.Back to the full paper2026 board paper, set 31/3/1: 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.