There are five classes of compounds in the premier division of endogenous plant growth regulators. These are auxins, gibberellins (GAs), cytokinins (CKs) abscisic acid (ABA) and ethylene. Broadly speaking, the auxins and GAs have been classified as regulators of cell elongation, the CKs as regulators of cell division. ABA as a general inhibiting influence and ethylene as a volatile with a finger in numerous