Ethylene in soil

Abstract

THE origin of ethylene in the soil atmosphere is of interest because the concentrations at which it sometimes occurs can restrict plant growth by inhibiting root extension in cereals¹ and root nodulation in legumes²; it has also been suggested that it aids plants by inhibiting pathogenic fungi³. Our earlier observations showed that ethylene could be produced by a soil fungus, Mucor hiemalis, and two soil yeasts, which have now been identified as Candida vartiovaarai and Trichosporon cutaneum, when glucose and methionine were available to them⁴. Subsequent investigations in pure culture and in soil have attempted to elucidate mechanisms by which these organisms could synthesise the gas^5–7. Other investigators^3,8 have proposed that anaerobic spore-forming bacteria rather than fungi are largely responsible for ethylene formation in soil as: (1) heat does not prevent the formation of the gas in soil, (2) anaerobiosis favours its formation and (3) the gas is fungi-static. Further experiments have therefore been undertaken in an attempt to assess if these latter observations cast doubt on our conclusions; the results are reported here.