(i) Three growth hormones in plants are :
(a) Auxin : It is synthesised in the young tip of roots and shoots. It promotes elongation and division of cell and root formation.
(b) Gibberellins : They help in the growth of the stem.
(c) Cytokinins : They promote cell division and delay leaf ageing.
(ii) The ability of a plant to detect change and respond to that change is termed as the sensitivity of the plant. Yet plants have no nervous system and no muscle tissue, they use electrical and chemical means to convey the information from one cell to another cell. The leaves of the sensitive plant (Mimosa pudica) folds up in response to touch. These leaf movement are independent of growth whereas, the directional movement of the shoot of a germinating seedling breaking through the soil is growth dependent
