Effects of chemical and heat treatments on ethylene production in soil |
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Authors: | J.B. Sutherland R.J. Cook |
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Affiliation: | Department of Plant Pathology, Washington State University, Pullman and Science and Education Administration, U.S. Department of Agriculture, Pullman, WA 99164, U.S.A. |
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Abstract: | Factors influencing C2H4 production in a silt loam were investigated in an effort to determine the source of this gas in soil. Air-dried samples of soil in glass vials were moistened to about ?10 kPa, sealed with rubber septa, and incubated at 30 or 35°C with an original atmosphere of air or O2-free N2. C2H4 concentrations in the vials were determined by gas chromatography.Addition of the antibacterial agents chloramphenicol or novobiocin to the soil inhibited C2H4 production, whereas the antifungal agent cycloheximide had no effect. Sodium azide and sodium cyanide also reduced C2H4 production. Treatment of the soil with moist heat (i.e. passing a steam-air mixture through it) at 80°C for 30 min failed to reduce the ability of the soil to produce C2H4 during subsequent incubation at 30°C, but autoclaving it twice at 121°C prevented C2H4 production. As with nonheated soil, C2H4 production from soil treated at 80°C was prevented by novobiocin but not by cycloheximide. Only about 10% of the bacteria isolated from nontreated soil were spore-formers. In contrast, 95–98% and possibly more of the bacteria isolated from heat-treated soil were spore-formers, including those in soil which was heat-treated and then incubated moist at 30°C for an additional 3 days before dilution plating. Addition of methionine had no effect on the production of C2H4 in anaerobic soil, whereas ethionine, chlorogenic acid, and ethylenediaminetetraacetic acid (EDTA) all enhanced C2H4 production. Ethionine, but not chlorogenic acid or EDTA, also resulted in considerable C2H4 accumulation in autoclaved soil; the C2H4 detected in ethionine-amended soil was apparently nonmicrobial in origin. Soil samples incubated at constant temperatures of 30, 50, or 70°C all produced C2H4.The results collectively indicate that C2H4 in soil is most likely produced by facultative or strictly anaerobic bacteria which are probably spore-formers and may also be thermophilic. Several isolates of spore-forming bacteria were inoculated into autoclaved soil, but none produced appreciable amounts of C2H4 under the test conditions. |
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