Auxin and phototropism
In order to survive, plants require light and water for A chemical process used by plants to make glucose and oxygen from carbon dioxide and water, using light energy. Oxygen is produced as a by-product of photosynthesis. Algae subsumed within plants and some bacteria are also photosynthetic.. They have developed responses called A growth response in a plant to a one-directional stimulus. to help ensure they grow towards adequate sources of light and water. This increases a plant's chance of survival.
The two main types of tropism are:
- positive tropisms 鈥 the plant grows towards the Any change in the environment that can be detected by receptors in an organism.
- negative tropisms 鈥 the plant grows away from the stimulus
Responses to stimuli of different parts of the plant
Growth of plant shoots towards the light. is a response to the stimulus of light.
- In the plant stem, responses to light are known as a positive phototropism, which means the stem grows towards the light.
- In the plant root, responses to light are known as a negative phototropism, which means the root grows away from the light.
Auxins
Plant hormones that control cell elongation. are a family of plant hormones. They are mostly made in the tips of the growing stems and roots, which are known as apical meristems, and can The movement of molecules from an area of higher concentration to an area of lower concentration. to other parts of the stems or roots.
Auxins are chemicals that control the growth of plants by promoting cell division and causing elongation in plant cells (the cells get longer).
Stems and roots respond differently to high concentrations of auxins:
- cells in stems grow more
- cells in roots grow less