What happens to the rate of photosynthesis when sunlight decreases?

What happens to the rate of photosynthesis when sunlight decreases?

• A. Increases
• B. Remains the same
• C. Decreases
• D. Becomes zero

Answer: (C)

Photosynthesis depends on light energy to drive the light-dependent reactions. When sunlight decreases, fewer photons are available to excite the chlorophyll and other pigments, so electron transport slows down and less ATP and NADPH are produced. That means the Calvin cycle has less energy to fix carbon, reducing the overall rate of sugar production. In other words, in typical conditions where light is the limiting factor, a drop in light directly lowers how fast photosynthesis can occur. The rate would only drop to zero if there were no light at all.

Photosynthesis depends on light energy to drive the light-dependent reactions. When sunlight decreases, fewer photons are available to excite the chlorophyll and other pigments, so electron transport slows down and less ATP and NADPH are produced. That means the Calvin cycle has less energy to fix carbon, reducing the overall rate of sugar production. In other words, in typical conditions where light is the limiting factor, a drop in light directly lowers how fast photosynthesis can occur. The rate would only drop to zero if there were no light at all.