Influence of water potential on production of ethylene in soil

Abstract

Ethylene production at different soil water potentials was studied in a high organic matter, red basaltic soil from a rain forest avocado grove of Queensland, Australia, and in a Latah silt loam from a recropped wheat field of Idaho, U.S.A. The soils were sealed under air or N2 in glass vials and incubated at 25 and 35 °C, respectively. Although the two soils differed in physical and chemical properties, in water content – water potential relationships, and in amount of ethylene produced, the relationship between ethylene production and water potential was virtually identical for both soils: maximal at saturation, reduced by −1 bar, and nearly prevented by −5 bars or slightly lower. Onset of ethylene production was earlier under N2, but total ethylene produced and the water potential–ethylene production relationship were about the same under both N2 and air. Osmotic adjustments of the soil water potential with KCl solutions resulted in more ethylene production between −1 and about −15 bars, but little or no ethylene production below −22 bars.The need for high water potential for ethylene production indicates that soil bacteria are more important than fungi in the ethylene production process in soil. The results further indicate that, because ethylene production is possible even to −5 bars or slightly lower, soil water availability should be no more directly limiting to this process in nature than it is, for example, to nitrification or other bacteriological processes in soil.