Which cycle can a plant perform without sunlight?

The Calvin cycle can occur without sunlight because it is the stage of photosynthesis that does not directly require light energy. This cycle takes place in the stroma of chloroplasts and relies on the products of the light-dependent reactions, specifically ATP and NADPH, which are generated when sunlight is available. However, the cycle itself can occur at any time, day or night, as long as the necessary ATP and NADPH are present.

While the light-dependent reactions and photosynthesis overall require sunlight to convert light energy into chemical energy (ATP and NADPH), the Calvin cycle's role is to utilize that chemical energy to fix carbon dioxide into glucose and other sugars. Therefore, it is essential for the continuous operation of the plant's metabolic processes even when sunlight is not available.