Question

Taking the example of auxins and cytokinins together, explain (i) a synergistic action in plants,(ii) an antagonistic action in plants.

Answer 1

The synergistic effect of auxin and cytokinin is that they both together helps in callus formation during plant tissue culture. This callus will then give rise to new plant. Auxin promote root formation and cytokinin promote shoot formation.
The increase in auxin concentration with respect to cytokinin will promote root formation. Similarly increase in cytokinin with respect to auxin will promote shoot formation. So auxin inhibits the effect of cytokinin and cytokinin inhibits the effect of auxin. This is known as the antagonistic effect of auxin and cytokinin.