The factors which prove the phytohormones act synergisticaUy or antagonitically are:
(a) Cell division is promoted by both auxins and cytokinins acting synergisticaUy.
(b) Auxin and cytokinins interact to control morphogenetic differentiation of shoot and root. When auxin is in excess, roots differentiate on the callus, while excess of cytokinins promote bud formation.
© Auxins and cytokinins acts antagonistically in controlling apical dominance. Auxins causes apical dominance, while cytokinins overcome the same.
(d) Senescence is prevented by auxins and cytokinins, while it is stimulated by abscisic acid.
(e) The activity of cambium and fruit growth seem to be promoted by auxins, gibberellins and cytokinins, the same is inhibited by abscisic acid.
(f) The dormancy of seeds and buds is mostly due to abscissic acid, the same is broken by gibberellins.
(g) Cytokinins cause opening of stomata, while abscisic acid results in their closure.
(h) The effects of auxin, gibberellins and cytokinins on
growth is antogonished by abscissic acid.