Respiration occurs in all cells of a plant. It utilizes sugars synthesized from sunlight through the process of photosynthesis into energy used by the plant at all times.
Respiration combines oxygen within a plant with stored sugars converted from photosynthesis. Photosynthesis is dependent on sunlight, while respiration does not require sunlight for activation and is constantly performed throughout the plant. Respiration is dependent on oxygen, and may be inhibited by over-watering or in soil incapable of proper drainage, which may deprive a plant's root system of necessary oxygen. A lack of oxygen may deprive a plant of nutrients and result in damage or its death.