Tropism

Tropism is the growth of a plant in reaction to something. There are a lot of types of tropism. Phototropism is a type of tropism where plants grow towards or away from a light source. Another is geotropism. Geotropism is the growth of a plant in response to gravity. Hydrotropism is when a plant grows towards or away from water. Thigmotropism is when a plant grows or turns in response to touch.

Geotropism(above)
Phototropism(below)

Hydrotropism:Tree reaching for creek(above)
Thigmotropism: Plant wrapping around pole(below)