Photo means light. The response of plant towards the environmental triggers, light which change the directions that plant parts grow in is called phototropism.
The directional, or tropic, movements can be either towards the light, or away from it. So, in two different kinds of phototropic movement, shoots respond by bending towards light while roots respond by bending away from it.
For example: Sunlight bends towards the sun from where the light is coming. This is the response of sunflower towards the plants.
