Ethylene Biosynthesis in Soil: I. Method of Assay in Conversion of 1‐aminocyclopropane‐1‐carboxylic Acid to Ethylene

Abstract

Abstract Ethylene (C 2 H 4 ) is a common biologically active secondary metabolite produced by soil microorganisms which can have a tremendous potential impact on crop yield. Methionine (MET) has been shown to be the major substrate for C 2 H 4 biosynthesis in higher plants and soil microorganisms. Although 1‐aminocyclopropane‐1‐carboxylic acid (ACC) is an intermediate in the conversion of MET to C 2 H 4 in plant tissues, the immediate precursor of C 2 H 4 and its biosynthetic pathway in soils has yet to be established. The primary objective of this study is to develop a method of assay to characterize the microbial conversion of ACC to C 2 H 4 in soil. Results showed that the rate of C 2 H 4 released from soil was enhanced with increasing pH (up to pH 9.0). The reaction rates of this transformation approached zero‐order kinetics when 9.9 m M ACC was added to soils. Under standard conditions, the accumulation of C 2 H 4 was linear with time of incubation for at least 7 d. Maximum reaction rates in the conversion of ACC to C 2 H 4 were observed at 50°C with enzyme denaturation occurring at 55°C. ACC derived‐C 2 H 4 production in soils was enhanced under highly oxidized conditions and severely inhibited under anaerobiosis. Among various pretreatments that affected the conversion of ACC to C 2 H 4 , toluene, CoCl, and oscillation enhanced C 2 H 4 biosynthesis, whereas, DMSO, formaldehyde, EDTA, 2‐mercaptoethanol, 2,4‐dinitrophenol, NaF, KCN, KNO 2 , and KNO 3 inhibited this reaction.