The reactions of the Calvin cycle are not directly dependent on light, but they usually do not occur at night. Why? (Explain your answer.)
a. It is often too cold at night for these reactions to take place.
b. Carbon dioxide concentrations decrease at night.
c. The Calvin cycle depends on products of the light reactions.
d. Plants usually close their stomata at night.

Question

The reactions of the Calvin cycle are not directly dependent on light, but they usually do not occur at night. Why? (Explain your answer.)

a. It is often too cold at night for these reactions to take place.

b. Carbon dioxide concentrations decrease at night.

c. The Calvin cycle depends on products of the light reactions.

d. Plants usually close their stomata at night.

Accepted Answer

Hi everyone. Welcome back. Let's look at our next question. It says which of the following statements best describes why the Calvin cycle is referred to as light independent reactions. Well, first we're going to recall from our content video the light dependent reactions in the Calvin cycle. Just to keep them straight. The light reactions are when you have the absorption of light energy by the pigments in the chlorophyll and the reactions their produce A T. P and N A D P A N A D P H. These go to provide energy for the Calvin cycle. The Calvin cycle is where you have carbon dioxide being converted to sugar again, driven by the A. T. P and N A V. P. H. That are produced in the light reactions. So with that in mind, let's look over answer choices. Choice A says the Calvin cycle occurs during nighttime. Well, this is not why the Calvin cycle is referred to as light independent. The Calvin cycle depends on the energy produced by the light reactions and those light reactions will not be taking place at night. So the Calvin cycle will not be going forward then. So Choice A is not correct. Choice B says, because this tomato is closed at night when the stabat A is closed, no new C. 02 will enter a leaf and the Calvin cycle depends on carbon dioxide to go forward for its carbon and its oxygen. So it will not take place when this tomato are closed at night since it can't access more C. 02. Choice C says the Calvin cycle does not require A. T. P. And any DPH produced from light reaction. Well, this here is false. The Calvin cycle does require the energy from those two, so that's not an answer. So finally, we're on a choice D. The Calvin cycle does not depend on light directly to initiate the reaction. And this is correct. The light cycles depend on light. That's how they absorb energy to Bruce that A. T. P. And N. A. D. P. H. But the Calvin cycle does not depend on this directly depends on the product products of the light reactions, but it doesn't need an input of light in itself for those processes to go forward. So that is why the Calvin cycle is referred to as light independent choice D. Because the Calvin cycle does not depend on light directly. See you in the next video.

Verified video answer for a similar problem:

Key Concepts

Calvin Cycle

Light Reactions

Stomata Function