| Ethylene (C(,2)H(,4)) production was monitored in twelve desert soils incubated moist at constant temperature for various incubation periods. In all but two soils with high organic matter content, C(,2)H(,2) production was low. Statistical analysis showed a good correlation between organic matter content and C(,2)H(,4) production. Minimum levels of C(,2)H(,4) were observed in saline and sodic soils.; Adding ethanol, glucose, glycerol and methionine to soil samples significantly increased C(,2)H(,4) formation. Methionine induced the highest level of C(,2)H(,4) in all soils tested. Increased concentrations of methionine resulted in further significant increases in C(,2)H(,4) production possibly indicating its role as a precursor for C(,2)H(,4). Chloramphenicol did not have a significant effect except in a saline soil suggesting that bacterial C(,2)H(,4) production is of less significance in the other soils.; The addition of salts to the high C(,2)H(,4) producing soils suppressed C(,2)H(,4) production most likely because of a direct effect on C(,2)H(,4) producing microorganisms through toxic salt levels, high osmotic pressure and/or increased pH.; Leaching of four saline soils and subsequent incubation resulted in significant increases in C(,2)H(,4) in two soils. Ethylene producers, previously inhibited by salinity, were probably reactivated when the salts were removed.; A Fusarium isolate obtained from the highest C(,2)H(,4) producing soil, produced the most C(,2)H(,4) in pure culture followed by isolates belonging to the genera Aspergillus, Penicillium, Curvillaria, and Rhizopus. In a comparative study, a number of species, some of which were known to produce C(,2)H(,4), were tested in culture media. Nine species produced C(,2)H(,4) in varying amounts of which Penicillium digitatum produced the highest concentration.; A sterilized saline soil produced significant C(,2)H(,4) when inoculated with spores of Mucor hiemalis and the Fusarium isolate, 5 to 14 times that in non-sterilized soil probably indicating an originally low population of C(,2)H(,4) producing organisms. The amounts of C(,2)H(,4) produced in sterilized inoculated mollisol and garden soils were only a fraction of that produced in non-sterilized samples probably indicating the involvement of a number of species in the production of C(,2)H(,4) in these soils. |
