Plant+Growth+Influenced+by+External+Environment


 * Definition:** Growth of plants toward or away from an environmental stimulus.
 * Negative Tropism**: movement away from stimulus
 * Positive Tropism**: movement toward the environmental stimulus
 * Nastic movements**: responses to stimuli are independent of the direction of the stimuli.

Types: Three main types are: Light, gravity and touch. (Hydrotropism and chemotropism) -Auxins cause the plant cells on the shaded side of the shoots to expand more rapidly than those on the lighted side.
 * Phototropism**: Response to light. They grow towards the light to get energy and photosynthesizes.
 * Geotropism**: plant growth response to gravity.
 * Thigmotropism:**Plant growth response to touch

- All the leaves in this photo are facing the light, performing phototropism.