Environment and Sporulation in Phytopathogenic Fungi IV. The Effect of Light on the- Formation of Conidia of Peronospora Tabacina Adam

Abstract

Using a leaf·disk technique, an analysis of the effect of light on the sporulation intensity of P. tabacina was carried out. The following points were demonstrated: (I) Under conditions of continuous light, sporulation of P. tabacina is sensitive to very low light intensities. ED5!1 for inhibition of sporulation was 16 ftvV cm- 2 for incandescent light (4 f,c.), and 0·58 p.W cm-2 for a monochromatic light source (469 mpo) in the region of maximum effectiveness. (2) Dark treatments induced sporulation under otherwise continuous light conditions. The response was directly proportional to the length of the exposure to darkness over the period 1·5-7 hr. (3) The time of day at which sporulation occurred could be modified by adjustment of the time of day at which darkness was initiated. (4) Within the visible spectrum, the region exerting maximal inhibition on sporulation occurred at 450-525 mJL.