RELATION OF OXYGEN PRESSURE AND TEMPERATURE TO GROWTH AND CARBON‐DIOXIDE PRODUCTION IN THE FUNGUS POLYSTICTUS VERSICOLOR

Abstract

THE EXPERIMENTS reported in this paper were planned to furniish information concerning the influence exerted by maintained temperature and mainitained oxygen pressure on mycelial growth and carbon-dioxide production in a strain of Polystictus versicolor Linn. (Fr.) growing on malt-agar strips in special culture tubes through which there was a continuous flow of water-saturated gas. The continuous gas stream served to maintain a known partial pressure of oxygen in each culture throughout the 5-day experiment period and also provided a satisfactory means for removing carbon dioxide as it was produced, delivering it to an absorber for measurement by titration at daily intervals. The data to be considered here represents nine different partial pressures of oxygen in the gas used and five different temperatures. The temperatures considered are 17.50, 21.50, 25.50, 29.50 and 33.5?C., and the oxygen pressures (measured as heights of mercury column) are approximately 0.0 mm. (practically pure nitrogen), 1.5 mm., 10 mm., 15 mm., 37 mm., 115 mm., 152 mm. (ordinary air), 381 mm. and 745 mm. (nearly pure oxygen). All combinations of these temperatures and oxvgen pressures are represented by growth data but there are no carbon-dioxide data for 33.50 combined with 0.0 mm. of oxygren pressure, nor for any of the temperatures combined with 10 mm. of oxygen pressure. Consequenltly the following discussions are based on 5-day experiments with each of forty-five and thirtynine different combinations of temperature and oxygen. pressure for growth and carbon-dioxide production, respectively. For all experiments excepting those with ordinary air the total pressure of the flowing gas was about 773 mm. (since gas for these was drawn from a highpressure storage cylinder provided with a HokePhoenix pressure-reducing valve), but the total pressure when ordinary air was used was lower, about 755 mm. (for this part of the study air was drawn by aspirator suction from the atmosphere). For the zero value of oxygen pressure, commercial nitrogen was employed, from which any oxygen present had been removed with alkaline solution of pyrogallol. For the highest oxygen pressure commercial oxygen was used, which was fouind to contain 95.5 per cent of oxygen bv volume. Intermediate oxygen pressures were secured by mixing the two commercial gases in requisite pressure proportions, in the manner described by Mack (1930). The daily rate of gas flow throughl each culture unit was always about 15 liters.