Give an example and explain how plants may immediately respond to a stimulus.
A. Mimosa pudica (touch me not plant) leaves has pad like swellings at the base 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 electrical impulse is generated. This impulse acts on plant hormones.
Because of this hormone 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 get firm and leaves become erect. This shows plants responding to a.certain stimulus.