Plants need sunlight to feed and grow. Without light, photosynthesis, the reaction by which the plant chloroplasts convert atmospheric CO2 and water into sugars and oxygen, cannot take place. In some situations, such as in forest areas or in high-density cultivated fields, plants compete with each other for sunlight. When a plant perceives the shade or the proximity of other plants, it activates a mechanism to elongate and grow more than the neighbouring plants. This mechanism is known as the shade avoidance syndrome (SAS).