A regulatory substance produced in an organism and transported in tissue fluids such as blood or sap to stimulate specific cells or tissues into action.These hormones help in regulation of the plant body by responding to the various signals from the plant and environment.The hormones are regulated in different tissues during the different development stages.There are five major hormones which are auxin, cytokinin, gibberellin, abscisic acid, and ethylene. Each hormone differs in its effects.The auxins, gibberellins, and cytokinins act as growth stimulators, whereas, abscisic acid and ethylene act as growth inhibitors. Plant hormones are simple in their structure as compared to those of animals or humans. There are no specific or specialized glands that produce these hormones. In fact, they are synthesized anywhere in the plant and act on any part as their target. Besides the hormones, there are manyplant growth factorsthat affect the function and growth of plants