Abscisic acid is a natural growth inhibitor. It promotes stomatal closure, ie, it is a stress hormone and helps the plant to cope with adverse environmental conditions especially drought. It also induces dormancy of seeds and buds. These seeds sprout only when ABA is overcome by GA.
Cytokinins overcome seed dormancy of various types including red light requirement of lettuce and tobacco seeds.
Application of gibberellic acid initiates the germination of dormant organ like buds and seeds.