Abscisic acid (also called stress hormone) is a mildly acidic growth hormone which function as a general growth inhibitor by counteracting other hormones (auxin, gibberellin, cytokinin) or the reactions mediated by them. ABA induced bud dormancy, seed dormancy, closure of stomata and stopage of cambial activity. LAA (Indole Acetic Acid) shows apical dominance, cell-enlargement and rooting in stem cutting.
Gibberellin (GA1) is secreted from the fungus Gibberella fujikuroi.
The most effective role of gibberellin is the internodal growth in some genetically dwarf varieties of plants like pea and maize.
Cytokinins are plant hormones which are essential for cytokinesis.
The auxin and cytokinin together cause differentiation of callus.