Photosynthesis is the reaction that lets plants store energy from the sun in the bonds of simple sugar molecules. Cellular respiration is the reaction that lets the plants then tap that stored energy for everyday activities such as growth and reproduction. The growth of plants is regulated by several hormones. Auxins are found in highest amounts near the tips of shoots and roots. They cause plants to grow longer by increasing cell length.
Auxins are the driving force behind plant tropisms.
A tropism is when a plant grows in a certain direction in response to environmental factors. In the case of phtotropism, more auxin is made on the shaded side of the plant, causing those cells to elongate, and thus the whole plant bends toward the light. In the case of geotropism, the upper side of roots growing horizontally make more auxin. This elongates the top cells, causing the root to turn downward. Gibberellins are hormones that are found throughout the plant.