VIEW ARTICLE

The Hypersensitive Reaction in Malus species: Changes in the Leakage of Electrolytes from Apple Leaves After Inoculation with Venturia inaequalis. E. D. Pellizzari, Departments of Biochemistry and of Botany and Plant Pathology, Purdue University, Lafayette, Indiana 47907; J. Kuc(2), and E. B. Williams(3). (2)(3)Departments of Biochemistry and of Botany and Plant Pathology, Purdue University, Lafayette, Indiana 47907. Phytopathology 60:373-376. Accepted for publication 29 September 1969. DOI: 10.1094/Phyto-60-373.

Conductance measurements indicated higher leakage of electrolytes from apple leaves of hypersensitive than either resistant or susceptible host-parasite combinations. The pattern of electrolyte leakage was verified using leaves from trees in an orchard and trees and seedlings grown in a greenhouse. A twofold increase in leakage was detected 22 hr before symptom expression in a clonal selection inoculated with races of the fungus to which it is hypersensitive, whereas leakage remained constant after inoculation with a race to which it is susceptible. These results suggest that increased cell permeability is associated with host response to the pathogen, and the magnitude of increase is greatest in hypersensitive host-pathogen combination. Some questions are raised concerning the induction of increased respiration and metabolism of phloridzin in relation to decompartmentalization and loss of host cell permeability.