Fruiting in Sphaerobolus with Special Reference to Light

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Abstract
Sphaerobolus grows and, provided there is sufficient illumination, fruits readily on oatmeal agar or on malt agar. No effect of light on vegetative growth can be demonstrated. On the malt medium, increased fruiting occurs with increase of nutrient up to 4 per cent, malt, but at higher concentrations fruiting is not increased and may be retarded. A chemically defined medium with starch as the carbon source allows fruiting, but at a low level. Temperature has a profound effect on basidiocarp development; above 25° C. no fruit-bodies are normally formed although vegetative growth is approximately optimal at that temperature. For overall fruit-body production at 20° C, light above 100 lux is necessary and light remains a limiting factor up to about 1, 000 lux. Under continuous light of suitable intensity, fruit-bodies continue to develop and discharge glebal-masses for many weeks. There is a distinct periodicity of discharge with (at 20° C.) about 12 days between peaks of activity. This corresponds with the time taken for basidiocarp initiation and development. A number of developmental stages of the basidiocarp are recognized. The final stage, glebal-mass discharge from stellately opened fruit-bodies, is indifferent to light, but all other stages are stimulated by light. The light intensity for effective stimulation falls during development and for the penultimate stage an intensity as low as 1 lux is effective. Only light of wave-length below 500 mμ is active in overall basidiocarp development. In the sensitive region between 400 mμ and 500 mμ, there appear to be peaks of sensitivity around 440 mμ and 480 mμ. In alternating light and darkness, simulating natural conditions, glebal-mass discharge occurs in the light periods. With a regimen of 24 hours light and 24 hours of darkness discharge is mainly in the dark periods.

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