how plants respond to stimuli?
For this question we have to take mimosa pudica plant as an example.Mimosa pudica leaves have pad like swellings at the base.they are called pulvini.Here cells contain lot of water and large intercellular spaces.Due to water pressure pulvini hold the leaf erect.Touch me not plant shows nastic movement by touch.This is called thigmonasty.when we touch the leaves,an electric impulse is generated,This impulse acts on plant harmone,Because of this harmone water in the pulvini cells which are closer to the leaf vein migrate to other side of the cells. Then pulvini loss its firmness hence leaves become fold After 20 to 30 minutes water comes back pulvini attains firmness and leaves become erect.