Acetaldehyde Oxime, A Product Formed during the In Vivo Nitrate Reductase Assay of Soybean Leaves

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Abstract
Evolution of nitrogen oxides (NO(x), primarily as nitric oxide) from soybean (G. max [L.] Merr.) leaves during purged in vivo nitrate reductase assays had been reported; however, these reports were based on a method used for determination of NO(x) in air. This method also detects other N compounds. Preliminary work suggested that the evolved N was not nitric oxide. Studies were undertaken to identify the N compound evolved from the in vivo assay reported as NO(x). Material for identification was obtained by cryogenic trapping and fractional distillation, and by chemical trapping procedures. Mass spectrometry, UV spectroscopy, and 15N-labeled nitrate were used to identify the compounds evolved and to determine whether these compounds were derived from nitrate. Acetaldehyde oxime was identified as the predominant N compound evolved and this compound is readily detected by the method for NO(x) determination. Substantial quantities of acetaldehyde oxime (16.2 .mu.mol/g fresh wt per hour) were evolved during the in vivo assay. Small amounts of nitrous oxide (0.63 .mu.g N/g fresh wt per hour) were evolved, but this compound is not detected as NO(x). Acetaldehyde oxime and nitrous oxide were both produced as a result of nitrate (15NO3-) reduction during the assay.