Respiration is essential for all living organisms and this includes plants. If respiration stops in a plant it will die, so plants constantly respire during the day and through the night. Respiration is a different process to photosynthesis, which depends on sunlight and therefore takes place only during the day.
Plants absorb the energy they need through aerobic respiration, which is a chemical reaction that uses the oxygen in the air and glucose from within the plant to form carbon dioxide and water. The plant derives the energy it needs to live from the water and carbon dioxide formed by the respiration process. To remain alive, the plant must respire at all times.
Respiration is linked to photosynthesis but the outcome is opposite. Photosynthesis uses energy from sunlight and the carbon dioxide in the air to produce oxygen. Respiration uses up oxygen and produces carbon dioxide. Overall, plants produce more oxygen than carbon dioxide and this is why plant life is an essential for animal life. Without plants, the earth's oxygen level would fall dramatically.
Not only do plants respire at all times, the rate of respiration remains constant throughout the day and night. In bright light, the rate of photosynthesis exceeds the respiration rate, while in dim light the rate is about the same. In darkness, photosynthesis stops but respiration continues at the same level.
All plants continue to respire during winter months, even the plants that lose their leaves for the winter. Respiration continues through all seasons, even though photosynthesis dramatically slows down or stops altogether. For respiration to carry on through the winter, plants use up stores of the food produced during the summer by photosynthesis.