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Question: Answered & Verified by Expert
Assertion : The higher concentration of \(\mathrm{O}_2\) in the atmosphere is inhibitory to photosynthesis.
Reason : \(\mathrm{CO}_2\) is the main substrate of photosynthesis.
BiologyPhotosynthesis in Higher PlantsAIIMSAIIMS 2008
Options:
  • A If both assertion and reason are true and reason is the correct explanation of assertion
  • B If both assertion and reason are true but reason is not the correct explanation of assertion
  • C If assertion is true but reason is false
  • D If both assertion and reason are false.
Solution:
2286 Upvotes Verified Answer
The correct answer is: If both assertion and reason are true but reason is not the correct explanation of assertion
Oxygen accumulation causes substantial inhibition of photosynthesis. Both oxygen evolution and $\mathrm{CO}_2$ assimilation were reduced in the presence of atmospheric oxygen. Oxygen causes a direct and indeed competitive inhibition of Ribulose diphosphate carboxylase. As a result glycolate synthesis is enhanced and leads to begin photorespiration. Carbon dioxide being one of the raw materials for photosynthesis, its concentration affects the rate of photosynthesis markedly. Because of its very low concentration in atmosphere $(0.03$ per cent only) it acts as a limiting factor in natural photosynthesis.

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