Plants are subjected to infection and attack by many different pathogens. However, the evolution of multiple defenses has allowed plants to effectively defend themselves against many of these attacks. Although many potential constitutive and induced defenses have been identified, the specific role and contribution of each to defense have been defined in only a few cases. Current research is involved in elucidating the nature and role of these defenses in several plant-pathogen systems using cytological, chemical, biochemical and molecular techniques. The major goals are to determine which mechanisms of defense are most important in the expression of resistance. Specific projects include the chemistry and role of phytoanticipins in periderm tissues of Prunus spp. as part of passive defense, the biochemical nature of defense against potato tuber pathogens, the role of natural and wound-induced periderm and suberin in potato tubers, and the uptake of chemicals by plants from the environment.