2010-07-222013-01-042011-07-232013-01-04195619561956http://hdl.handle.net/10388/etd-07222010-135710New and highly refined physiological techniques have largely replaced the descriptive methods of classical cytology originally used in the investigation of host-parasite relations (Shaw and Samborski, 1956; Samborski and Shaw, 1956). Physiological as contrasted to cytological methods, however, usually do not permit distinction between the members of the host-parasite complex or detection of host reactions at the cellular level. With such methods, therefore, it is virtually impossible to investigate the vegetative phase of obligate parasites or to analyze host reactions when these are limited to one or a few cells as, for example, the initial changes following infection of susceptible hosts and the localized reactions of highly resistant hosts. The present research was initiated on the premise that certain aspects of host-parasite relations could best be investigated by histochemical methods since these provide a combined cytological-physiological approach.en-UStext