What are plant hormones? Name the plant hormones responsible for the following

(i) Growth of stem

(ii) Promotion of cell division

(iii) Inhibition of growth

(iv) Elongation of cells

Plant hormones are chemicals or signal molecules produced by plants and occur in small concentrations.
i) Auxin: The primary function of the auxin is to elongate plant cells in the stem. For instance, auxins are the hormones responsible for phototropism, the growth of a plant toward the light.
ii) Cytokinin’s: They promote cell division. The extent of their effect depends on the concentration of auxin.
iii) Abscisic acid and ethylene inhibit plant growth.
iv) Gibberellins promote stem elongation. They are produced in the stem, buds, and root tips.