Key Points
Key Points: Plant Growth Regulators
- PGRs (phytohormones) are classified into two groups - growth promoters (auxins, gibberellins, cytokinins) and growth inhibitors (abscisic acid, ethylene).
- Growth promoters help in cell division, enlargement, flowering, fruiting and seed formation; growth inhibitors respond to stress and control dormancy and abscission.
- Auxin - discovered by Charles & Francis Darwin (phototropism in coleoptiles), isolated by F.W. Went. Gibberellins - discovered from "bakanae" disease in rice by E. Kurosawa.
- Cytokinins - discovered by F. Skoog through tobacco stem callus, identified as kinetin. ABA - identified in the mid-1960s from inhibitors by independent researchers.
- Ethylene - discovered by H.H. Cousins, the only gaseous PGR
