Application of the acetylene reduction method in nitrogen fixation studies

Abstract

Abstract The fixation of atmospheric nitrogen by organisms has usually' been measur'ed by the increase in t6tal nitrogen using the Kjeldahl method and, recently, by enriching with 15N isotope using a mass spectrometer after a suitable period of incubation. However, the Kjeldahl method is in accurate, laborious and not sensitive. The isotope UN method is 30 to 100 times more sensitive than the Kjeldahl method, but it is expensive and requires that the experiment is conducted only on a small scale, creating conditions quite different from the natural environment. The method also requires a mass spectrometer. More recently, DILWORTH (1) and SCHOLLHORN and BURRIS (2) observed that acetylene is reduced to ethylene by extracts from Clostridium pasteurianum. Ethylene production in the acetylene-reducing function of nitrogen-fixing microorganisms was determined by gas chromatographic techniques. The acetylene reduction method has been used in the detection of nitrogenase in biological systems (3,4,5,6). The method is reported to be simple, economical and a thousand times more sensitive than the liN method (6). This paper is a preliminary report on the use of the acetylene reduction method in studies on nitrogen fixation of various kinds of materials in the rice fields.