The factors which prove the phytohormones act synergistically or antagonistically are:
(i) Cell division is promoted by both auxins and cytokinins acting synergistically.
(ii) 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.
(iii) Auxins and cytokinins acts antagonistically in controlling apical dominance. Auxins causes apical dominance, while cytokinins overcome the same
(iv) Senescence is prevented by auxins and cytokinins, while it is stimulated by abscisic acid.
(v) The dormancy of seeds and buds is mostly due to abscisic acid, the same is broken by gibberellins.
(vi) Cytokinins cause opening of stomata, while abscisic acid results in their closure.