STUDIES ON THE EFFECT OF LASER ON THE GROWTH AND METABOLISM OF SOME MICROORGANISMS

Abstract

THE present investigation aimed at studying the effect oflaser radiation on the spore gennination, radial growth • rate, • • • sporulation or sclerotia!production, leakage of electrolytes and sugars from the mycelium, nucleic acids synthesis, cellulolytic and pectinolytic activities of 2 soilbome plant pathogens, Fusarium oxysporum f. sp. lycopersici and Sclerotium cepivorum which cause tomato wilt and white rot of onion, respectively. Two types of laser were used in this study which were C02 and Nd-YAG lasers. Increasing doses of radiation ' . were investigated over a range of power level and times. The C02 laser was applied as continuous mode at power level ranging from 0.5 to 15.0 W for periods of2-8 seconds. Nd­ YAG laser irradiation at wavelength of 355 nm was employed • at 30 pulses/second at a power level ranging from 2-8 MW for periods of 10-80 seconds and the total energy delivered ranged from 4.2 to 134.4 J.

The reached results are summarized in the following:

0 The C02 laser irradiation induced effects ranging from death of the test pathogen to partial or no inhibition or even :•.. .. stimulatory effects. Significant inhibition for spore germination, radial growth, sporulation of F. oxysporum f. sp. lycopersici were established when the C02 laser irradiation was applied at power levels equal or more than 2.0 W. S. cepivorum was more sensitive to C02 laser than F. oxysporum f. sp.