EFFECTS OF ETHYLENE ON ROOT EXTENSION AND NODULATION OF PEA (PISUM-SATIVUM-L) AND WHITE CLOVER (TRIFOLIUM-REPENS L)

Low concentrations of ethylene, comparable with those known to occur in anaerobic soil, inhibited extension of pea roots to a similar extent to that previously reported for barley. Thus pea apparently was less sensitive to ethylene than some non-leguminous dicotyledons. Perfusion of 10ppm of ethylene through the soil around the roots of pea and white clover resulted in reduced shoot dry weight. Nodulation, and the nitrogenase activity of those nodules which did form, was also greatly reduced. The ecological consequences of the sensitivity of nodulation and N fixation to ethylene, and the possible significance for quantitative studies involving the acetylene-reduction assay, are discussed.