Biological and biochemical methods, based on glufosinate inhibitory effects on plant growth and nitrogen metabolism, were examined for their applications to detect this herbicide. Dose–response analysis of radicle growth inhibition showed that, among six vegetables tested, Chinese mustard and edible amaranth were the most sensitive to glufosinate. Field mustard and cruciferous Ching-Geeng were found to be more sensitive to this herbicide than the other four vegetables when three-leaf seedlings were tested in another bioassay. In three-leaf seedlings of Ching-Geeng, accumulation of ammonium, a biochemical marker for glufosinate toxicity because of its inhibition of glutamine synthetase, showed a linear regression to the log-transformed concentrations of glufosinate ranging from 7.5 × 10−5 to 1.5 × 10−3 M. For the detection of glufosinate lower than 7.5 × 10−6 M, a linear regression was observed between ammonium accumulation and the applied concentration, instead of the log-transformed value, of glufosinate. A similar relationship was observed between the accumulation in Ching-Geeng seedlings of glyoxylate, another biochemical marker, and glufosinate but with a narrower range than that for ammonium accumulation. The applicability of ammonium accumulation in three-leaf seedlings of Ching-Geeng to detect glufosinate residue in water and soil was confirmed by high-performance liquid chromatography (HPLC).
Nomenclature: Glufosinate; Chinese mustard, Brassica rapa L.; field mustard, Brassica campestris L.; cabbage, Brassica oleracea L. var. Capitata; Ching-Geeng, Brassica chinensis L., ‘Ching-Geeng’; edible amaranth, Amaranthus tricolor L.