(a) Plants do not have any nervous system but yet, if we touch a sensitive plant, some observable changes take place in its leaves. Explain how could this plant respond to the external stimuli and how it is communicated.(b) Name the hormone that needs to be administered to (i) increase the height of a dwarf plant.(ii) cause rapid cell division in fruits and seeds.

(a) Plants do not have any nervous system but yet if we touch a sensitive plant, the touch me not (Mimosa pudica) plant folds its leaves when it is touched, this phenomenon is known as thigmonasty.

External stimuli trigger an action of cells due to which there is a sudden loss of water from leaves and leaves get a fold. The leaves open themselves and return to their original state after a few minutes.

 

(b)

(i) increase the height of a dwarf plant: Gibberellins

(ii) cause rapid cell division in fruits and seeds: Cytokinin.