Define a plant hormone. Compare plant hormones to human hormones according to their definition. List the functions and characteristics of hormones, their chemistry and attachment to target cell receptors. Discuss how hormones affect growth, metabolic activity, and cell/tissue development. Describe how receptors must be specific for hormones, chemically they must "fit" together in order for a reaction to occur. Begin plant hormones by discussing auxins, the first plant hormones discovered. Discuss that they function as growth stimulants.