Sporophore Production in Sphaerobolus with Special Reference to Periodicity

Further observations on temperature and fruiting are reported.The minimum and optimum values depend on the time when observationsare made. The effect on discharge from sporulating culturesof illumination interrupted by dark periods (i-ii days) is considered.If the dark period does not exceed a day, harge recommenceson the second and subsequent days of renewed illumina if itis 2–4 days, discharge occurs on the second day afterreturn to light but not thereafter; if the period of darknessexceeds 5 days, discharge does not mmence on subsequent illuminationuntil a completely new crop of sporophores is formed. Experiments are reported in which it is shown that at 20°C there is an interval of about I day between the onset of adark period and the inhibition of discharge related to it. Thisperiod is increased to a day and a half at 10° C. At thistemper an alternation of roughly equal light and dark periodseach day leads to dis in the dark periods and not in the lightperiods as at 20° C. Experiments are reported which support the view that the long-termof discharge in cultures under constant conditions relates toinhibition of development of primordia by maturing sporophores.     

Carbon Dioxide and Fruiting in Sphaerobolus

In cultures bathed in air deprived of its CO² fruiting in Sphaerobolusis greatly reduced or fails completely. However, increasingthe concentration of CO² in the air to 1or 5 per cent tendsto reduce fruiting as compared with normal air. The stimulatoryeffect of CO² in normal air appears to be exerted at the stageof development when sporophore primordia are being produced.The CO² does not seem to require the immediate presence of lightto exert its effect. It has not been found possible to replacethe effect of CO² by substituting Krebs-cycle organic acids.Using ¹⁴CO² it is shown that ¹⁴C is incorporated in the myceliumboth in light and in darkness.     

Some Effects of Light on Excised Wheat Roots with Special Reference to Peroxide Metabolism

When excised wheat roots are exposed to blue light, catalase activity changes in a way to he expected as a result of photodestruction with first order kinetics. Wheat root catalase in vivo is less light sensitive than animal catalase in vitro, possibly due to internal screening. Illumination of the roots with red light causes some increase in catalasc activity. Peroxidase activity is much less affected by light. No relation has been found between catalase destruction and chlorophyll formation. The ability of roots to oxidize pyrogallol to purpurogallin (by other workers interpreted as peroxide production) is decreased by light, especially blue light. On the contrary, one peroxide producing enzyme, glycolic acid oxidase, was detected only in roots grown in blue light. The total flavin content, or the fraction present as FAD, is not affected by light. The ascorbic acid content is low, but slightly increased by blue light.     

Sporophore Development in Sphaerobolus: Effect of Blue and Red Light

Experiments are described which indicate that, although lightof short wavelength (400–500 mµ) is necessary forover-all sporophore development, during the last days of theprocess light of longer wavelength (640–720 mµ)accelerates development more than blue light (400–500mµ) does. It is shown that at 20° C this effect ofthe longer rays of light begins to be exerted 8 to 10 days aftersporophore initiation and only a very few days before maturity.