Ethylene Accumulation in Soil in Response to Organic Amendments

One of the major factors affecting ethylene (C 2 H 4 ) accumulation in soil is the availability of organic substrates. Various organic compounds were screened for their stimulatory effect on C 2 H 4 accumulation in soil. Since L‐methionine (L‐ met ), a sole precursor of C 2 H 4 synthesis in plants, is also an excellent precursor for microbial biosynthesis of C 2 H 4 , all the compounds tested were added on a C‐equivalent basis with respect to 1 g L‐ met kg −1 soil. Incubation was carried out under ambient conditions (24 ± 3 °C) for 14 d and the soil was maintained at field capacity (−33 kPa). Among the 63 compounds tested, the majority of amino acids, organic acids, carbohydrates, proteins, alcohols, and met analogs promoted C 2 H 4 generation to a greater degree than did the unamended soil. Use of 1‐aminocyclopropane‐1‐carboxylic acid ( acc ) enhanced C 2 H 4 synthesis much more than any other treatment (2400‐fold over the unamended nonsterile control). Of the five vitamins tested, inositol was the most effective in promoting C 2 H 4 production. L‐Ethionine (L‐ eth ) was an excellent precursor among the five met analogs. Nonbiological production of C 2 H 4 was observed only upon treatment with L‐ met , L‐cysteine, acc , ethanol, and L‐ eth , which were 7.9, 19.0, 3.0, and 4.2% and 2.1‐fold, respectively, of the total C 2 H 4 detected under nonsterile amended conditions. Since the majority of these compounds are excreted by plant roots, the rhizosphere may be an active site for C 2 H 4 generation.