1. Tropism
Directional growth of a plant, or part of a plant, in response to an external stimulus such as gravity or light.

2. Phototropism
Movement or growth in response to light

3. Gravitropism
Movement or growth in response to gravity

4. Hydrotropism
Movement or growth in response to touch or contact

5. Thigmotropism
                                                         
Movement or growth in response to touch or contact

6. Thermotropism
The tendency of plants or other organisms to bend toward or away from heat.