If the movement is happening due to a response to gravity or light (directional movement either towards or away from the stimulus), it's called "Tropism". If the movement is caused by something else, its called "Nastic movement".

Nastic Movement- Plant movement that is caused by an external stimulus, but is directionally independent of its source (such as a change in water pressure inside cells).

thermonasty - movement caused by an increase or decrease in temperature

photonasty - movement due to light (but not a negative or positive response) such as the opening and closing of flowers due to the light cycle. Not the same thing as tropism.

haptonasty - movement caused by tactile stimulus (such as in the Venus flytrap)

nyctinasty - movement caused by darkness

hydronasty - response to a change in humidity

chemonasty - response to a chemical stimulus


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