Fruiting in Sphaerobolus with Special Reference to Light

Sphaerobolus grows and, provided there is sufficient illumination,fruits readily on oatmeal agar or on malt agar. No effect oflight on vegetative growth can be demonstrated. On the maltmedium, increased fruiting occurs with increase of nutrientup to 4 per cent, malt, but at higher concentrations fruitingis not increased and may be retarded. A chemically defined mediumwith starch as the carbon source allows fruiting, but at a lowlevel. Temperature has a profound effect on basidiocarp development;above 25 C. no fruit-bodies are normally formed although vegetativegrowth is approximately optimal at that temperature. For overallfruit-body production at 20 C, light above 100 lux is necessaryand light remains a limiting factor up to about 1, 000 lux.Under continuous light of suitable intensity, fruit-bodies continueto develop and discharge glebal-masses for many weeks. Thereis a distinct periodicity of discharge with (at 20 C.) about12 days between peaks of activity. This corresponds with thetime taken for basidiocarp initiation and development. A number of developmental stages of the basidiocarp are recognized.The final stage, glebal-mass discharge from stellately openedfruit-bodies, is indifferent to light, but all other stagesare stimulated by light. The light intensity for effective stimulationfalls during development and for the penultimate stage an intensityas low as 1 lux is effective. Only light of wave-length below500 mµ is active in overall basidiocarp development. Inthe sensitive region between 400 mµ and 500 mµ,there appear to be peaks of sensitivity around 440 mµand 480 mµ. In alternating light and darkness, simulating natural conditions,glebal-mass discharge occurs in the light periods. With a regimenof 24 hours light and 24 hours of darkness discharge is mainlyin the dark periods.