what causes phototropism in plants
Phototropism. Phototropism is a plant's growth response to light. Plants need light to grow. Usually, plant shoots and stems exhibit a positive reaction to light (they grow towards the light source). The ability to grow towards sunlight gives the plants an evolutionary advantage.tudies have shown that plant hormones of the class of auxins play a key role in this directed growth process. Auxin is released into the cells on the plants shady side. There, the hormone stimulates the cell walls to elongate. Also, growth is inhibited on the plant's sunny side.