Movement or growth of any part of the plant in response to an external stimulus is called tropic movement or tropism.
The different types of tropic movements are:
- Phototropic movement : The shoot system of any plant responds to the light stimulus, i.e., it grows towards the source of light. The movement shown by plants towards the source of light is called phototropic movement.
- Gravitropic movement : The root system of plants responds to stimulus of gravity. This is called gravitropic movement.
- Hydrotropic movement : The root system of plants responds to the stimulus of water. This is called hydrotropic movement.
- Chemotropic movement : Movement shown by plants in response to specific chemicals is called chemotropic movement. For example, the growth of the pollen tube towards the ovule.
All the above-mentioned movements of plants are related with growth, hence are called growth relevant movement.