| Abstract: | The interaction of several environmental factors with varying rates of CO₂ on sclerotial survival of Phymatotrichum onmivorum was studied. Sclerotia of P. omnivorum were placed in sealed glass culture chambers and aerated with 0.03%, 5%, and 50% CO₂. Autoclaved and nonsterile Houston black clay was used in the chambers. Water was added to bring the systems to their moisture holding capacity. The chambers were incubated at 20C and monitored at 0, 30, and 90, and 180 days. Soil and surface gaseous concentrations were determined. The CO₂ concentrations in both the autoclaved and nonsterile soil increased for varying amounts of time regardless of CO₂ treatment and this increased could be attributed to microbial activity or the presence of sclerotia in the system. In those systems with high initial concentrations of CO₂ there was a sharp decrease in CO₂ concentrations between 30 and 90 days. This may have resulted from leakage in the system or CO₂ fixation by the microorganisms. The soil pH values were determined by a CaCl₂ method. In the high CO₂ treatments, CO₂ appeared to be absorbed in the soil water resulting in low initial pH values. After 30 days the pH values were very similar in both autoclaved and nonsterile soil regardless of treatment. The maximum values were obtained at 90 days in the autoclaved and nonsterile soil. |
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