Hormones

hormones, natural substances present in trace concentrations in vines and other plants which move from one organ or part of the plant to another to regulate growth and development. Synthetic growth regulators may have similar chemical structures, and a similar mode of action. There are three groups of hormones which promote growth, these being auxins, gibberellins, and cytokinins, and two groups which inhibit growth, abscisic acid and ethylene.