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BotanyNEET 2024Calvin cycle, C4 pathway, photorespiration

Photosynthesis in Higher Plants

Given below are two statements:

Statement I: In C₃ plants, some O2\mathrm{O_2} binds to RuBisCO, hence CO2\mathrm{CO_2} fixation is decreased.

Statement II: In C₄ plants, mesophyll cells show very little photorespiration while bundle sheath cells do not show photorespiration.

In the light of the above statements, choose the correct answer from the options given below:

  1. A.Both Statement I and Statement II are false
  2. B.Statement I is true but Statement II is false✓
  3. C.Statement I is false but Statement II is true
  4. D.Both Statement I and Statement II are true

Solution

In C₃ plants RuBisCO's oxygenase activity binds O2\mathrm{O_2} and lowers CO2\mathrm{CO_2} fixation — Statement I true. In C₄ plants photorespiration is avoided because bundle-sheath cells (where RuBisCO sits) are kept CO2\mathrm{CO_2}-rich; the statement's reversal of which cells photorespire is wrong — Statement II false.

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