Some complimentary effects of plant growth regulators:
Gibberellins: Synthetic substances found with gibberellins known as anti gibberelins blocks the biosynthetic pathway of gibberellins.e.g. prohexadione, daminozide etc. GA3, a type of gibberellin inhibits the growth of callus.
ABA (abscisic acid): It is regarded as the plant growth inhibitor because of its involvement in bud dormancy and abcission. Also, it inhibits callus growth.
Ethylene gas: It inhibits growth in dicotyledonous shoots. e.g. peas.