THE EFFECT OF RADIANT ENERGY ON GROWTH AND SPORULATION IN COLLETOTRICHUM PHOMOIDES

Abstract

Experiments were performed on Colletotrichum phomoides, a fungus which is a common cause of ripe-rot on tomatoes.The lines of the mercury arc spectrum may be grouped into three classes on the basis of their effect on the growth of Colletotrichum: those which cause constant retardation, those which cause constant stimulation and those which cause primary retardation followed by stimulation.On the basis of the effect on the production of spores, there are two classes of lines in the mercury arc spectrum, i.e., those which hasten spore development and those which have no apparent effect. Spore production is generally hastened by monochromatic light causing retardation or extreme stimulation of growth, and is apparently not affected by light which moderately stimulates growth; moreover, an optimum duration is shown for the illumination causing the accelerated development of spores.Evidence is given that the effect of monochromatic light is upon the protoplasm and not the culture, since cultures grown on non-irradiated media from irradiated spores show the same effects as those obtained by irradiating three-day cultures. In many cases, in Colletotrichum, the effect of irradiation is evident in the culture 10 days after the spores have been illuminated.There is a marked similarity in the effect upon the growth of Colletotrichum, Yeast and Paramoecium.