The metabolism of the herbicide ¹⁴C-glufosinate (GA) was studied in excised shoots and leaves of 20 weed and nonweed species; GA was fed through the xylem. After 24 or 48 h of incubation, the plant material was examined for phytotoxic symptoms, analyzed by autoradiography, and extracted. The extract was cleaned up and analyzed by high-performance liquid chromatography. GA and its metabolites were identified by cochromatography with authentic ¹⁴C-labelled reference compounds. ¹⁴C-GA was rapidly absorbed by the excised plant parts. Most of the radioactivity (91.3 to 99.7%) in the shoots and leaves was extractable. The main metabolite observed with all species was 3-(hydroxymethylphosphinyl)propionic acid (MPP); lower amounts of 2-hydroxy-4-(hydroxymethylphosphinyl)butanoic acid (MHB) were also found in 14 species. Metabolic rates of GA varied considerably ranging between 13.1 and 2,836.5 ng GA h⁻¹ mg⁻¹ protein. The species with the highest rates of metabolism of GA were Galium verum (2,836.5 ng GA h⁻¹ mg⁻¹ protein), Lythrum hyssopifolia (846.0 ng GA h⁻¹ mg⁻¹ protein), and Digitalis purpurea (494.8 ng GA h⁻¹ mg⁻¹ protein). The mean value across all species was 275.9 ng GA h⁻¹ mg⁻¹ protein.

Nomenclature: GA, glufosinate (racemic mixture); DGA, D-glufosinate; LGA, L-glufosinate; MHB, 2-hydroxy-4-(hydroxymethylphosphinyl)butanoic acid (racemic mixture); MPA, 2-(hydroxymethylphosphinyl)acetic acid; MPB, 4-(hydroxymethylphosphinyl)butanoic acid; MPP, 3-(hydroxymethylphosphinyl)propionic acid; PPO, 2-oxo-4-(hydroxymethylphosphinyl) butanoic acid; Agrostemma githago L. AGOGI, corn cockle; Alopecurus myosuroides Huds. ALOMY, blackgrass; Amaranthus retroflexus L. AMARE, redroot pigweed; Avena fatua L. AVEFA, wild oat; Camelina alyssum Mill. Hegi Schmid CMAAL, flatseed falseflax; Chelidonium majus L. CHQMA, greater celandine; Chenopodium album L. CHEAL, common lambsquarters; Digitalis purpurea L. DIKPU, foxglove; Fumaria officinalis L. FUMOF, fumitory; Galium aparine L. GALAP, catchweed bedstraw; Galium verum L. GALVE, yellow bedstraw; Geum urbanum L. GEUUR, common avens; Geranium robertianum L. GERRO, herb-robert; Lolium perenne L. LOLPE, perennial ryegrass; Lythrum hyssopifolia L. LYTHY, hyssop loosestrife; Malva sylvestris L. MALSI, high mallow; Matricaria chamomilla L. MATCH, wild chamomile; Poa pratensis L. POAPR, Kentucky bluegrass; Brassica kaber (DC.) L. C. Wheeler SINAR, wild mustard; Daucus carota L. DAUCA, wild carrot, ‘Maxima.’