Light and the Development of Poria ambigua

Abstract

In the course of investigations on the nutrition of some of the Basidiomycetes, it was noted that a culture of Poria ambigua Bres. from Ross W. Davidson, his number 86357, formed basidiospores in the light but produced few or none in the dark. The influence of light on the development of many fungi is well known and an extensive literature on the subject exists which will not be reviewed here. Our preliminary observations indicated that Poria ambigua in its response to light might be an especially favorable subject for investigation. Methods and Materials.-The basal medium 1 employed contained mineral salts, dextrose, casein hydrolysate, various purine and pyrimidine bases and the known B vitamins. The hydrion concentration was approximately pH 4.5. Cultures were grown in triplicate or quintuplicate at 25? C in 20 x 100 mm petri dishes containing 20 ml of medium, solidified with 1.5 per cent Difco agar or in 125 ml Erlenmeyer flasks which contained 25 ml of liquid medium. Our standard inoculum was obtained from colonies which had grown three or four days at 25? in the dark. Inoculum, unless otherwise stated, consisted of bits of mycelium 1 mm or 5 mm in diameter taken 3 or 4 mm from the edge of the colony by the method described by Yusef (1953). After inoculation, the dishes were wrapped individually in aluminum foil and incubated in a light-tight incubator at 25?. Unless otherwise indicated, the light to which cultures were exposed was a mixture of diffuse daylight and artificial light totaling from 200 to 280 foot-candles (ft-c). Natural Materials and Growth.-Poria ambigua grew in our basal medium. However, growth of the fungus as measured by dry weight