The Problem of Acquired Physiological Immunity in Plants

Abstract

A KNOWLEDGE of the principles underlying the reactions of a host attacked by a parasite has been of inestimable value in the understanding and control of human diseases. So, too, phytopathology has found that the study of immunity and susceptibility has made possible much of its progress in recent years. Three of the major advances in the present century in plant pathology are closely dependent upon a knowledge of the factors of immunity and susceptibility, namely, the breeding for disease resistance, the discovery of the significance of biological races, and the study ol the effect of environment upon plant disease. The ability of the animal to resist infection by the acquirement of a state of partial or complete immunity, contingent upon sensitization by the parasite, is the basis of the most important recent advance in medicine, serotherapy. Accordingly, plant pathologists have not failed to recognize the important theoretical and practical advantages of a knowledge of the role of acquired immunity in plants. As early as I9OI Ray and Beauverie offered the first suggestions regarding a display of immunological reactivity in plants comparable to that in animals. Many other plant pathologists, physiologists, and geneticists have since considered this possibility in theory, in observation, and in experiment. This type of work is comparatively unknown to American investigators which is due, in part at least, to the fact that there has appeared no adequate analysis of this field of study in English. The writer, when questioned regarding acquired immunity in plants has repeatedly been forced to direct his interrogators to the excellent monograph of Carbone and Arnaudi (47), which being in Italian cannot be studied freely by most American botanists. To the intensive student in the field of plant immunity this work is a most valuable contribution, but to the botanist who does not specialize in immunology yet who wishes to be informed upon this subject, the work of Carbone and Arnaudi is usually assimilated with such difficulty