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Physiology and Biochemistry

Effect of Monochromatic Light on Germination of Oospores and Formation of Sporangia of Phytophthora citricola. D. F. Plourde, Graduate research assistant, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907; R. J. Green, Jr., professor, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907. Phytopathology 72:58-61. Accepted for publication 14 May 1981. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-58.

Oospore germination and sporangial formation of Phytophthora citricola in various bands of monochromatic light were studied. Acrylic filters with spectral transmission peaks at 450, 545, 650, and 750 nm were combined with aqueous filter solutions and various light sources to expose oospores to a radiant flux density of 20 ergs/cm2/sec. Oospore germination and sporangial formation occurred in the dark, but exposure to light greatly enhanced both processes, especially in the blue (400420 nm) and ultra-violet (350400 nm) portions of the spectrum. Increasing periods of exposure to monochromatic light enhanced sporangial formation, but had little effect on oospore germination. When the intensity of far-red (750 nm) light was increased from 20 to 320 ergs/cm2/sec both oospore germination and sporangial formation decreased.