The thesis begins with an introduction to signal transduction and an analysis of current understanding of plant signal transduction. There are similarities between plants and animals, but also key differences, including lack of protein kinase C and of a cAMP signaling pathway in plants, and presence in plants of calcium dependent protein kinase (CDPK), which has a kinase catalytic domain contiguous with a C-terminal calmodulin-like domain. The next section examines protein kinase activity in the plasma membrane (PM) of zucchini hypocotyls. Zucchini PM contains four or more polypeptides with calcium-requiring protein kinase activity. The enzymes appear to be tightly associated with the PM, and at least three are recognized by monoclonal antibody to soybean soluble CDPK. Total proteins from several different organs of zucchini seedlings contain kinases with molecular weights similar to the hypocotyl PM enzymes. In the third section details of partial purification of the solubilized PM kinases are presented. Kinases which do not crossreact with anti-CDPK monoclonal antibody were resolved by anion exchange from ones which do crossreact. Peptide mapping was used to test the relationship between the kinases. Results of peptide mapping suggest that at least three types of protein kinase are present in zucchini PM, two of which are immunologically similar to CDPK and one of which is not. The last section concerns the potential for testing interactions between PM protein kinases and plasma membrane auxin binding proteins (ABP's) by use of photoaffinity labeling of ABP's. Causes of variable photoaffinity labeling by an azido-IAA are considered. Labeling of both the tomato mutant diageotropica and the parent VFN membranes was inexplicably inconsistent. / Graduation date: 1994