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Question 30

A graph of rate of photosynthesis against light intensity rises and then becomes horizontal. Which statements about that horizontal part are true? Select all that apply.

  1. The plant has decided it has made enough sugar and has stopped
  2. Light has stopped being the factor that limits the rateCorrect answer
  3. Photosynthesis has stopped altogether in the leaf
  4. Some other requirement is now capping the rateCorrect answer

Explanation

Adding light stops making any difference once the reaction is capped by something else it needs, which is why the line flattens although the lamp keeps getting brighter. The reaction has not shut down, and the idea that a plant decides it has made enough sugar has no mechanism behind it, since nothing in a plant switches the reaction off when supplies are good.

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Question 30: A graph of rate of photosynthesis against light intensity… · Plants and Photosynthesis · Questena