If a plant is kept in the dark, what will it not perform?

The ability of a plant to undergo photosynthesis is directly linked to the presence of light. The light-dependent reactions, which occur in the thylakoid membranes of the chloroplasts, require light to activate chlorophyll and other pigments. These reactions are responsible for capturing sunlight energy to convert ADP and NADP+ into the energy carriers ATP and NADPH, as well as splitting water molecules to release oxygen.

In the absence of light, these light-dependent reactions cannot take place; hence the plant cannot perform the processes integral to producing ATP and NADPH, which are crucial for the subsequent steps of photosynthesis.

While the Calvin cycle can still occur in the dark using the ATP and NADPH produced during previous light-dependent reactions, it ultimately cannot function optimally without a continual replenishment of these energy carriers. Cellular respiration and other metabolic processes are also unaffected by light, as they do not require light to generate energy from stored organic molecules.