Metabolism of 4-nitrophenol in aseptically cultivated plants of the species wheat ( Triticum aestivum L.), soybean ( Glycine max L.), wild oat ( Avena fatua L.) and corn cockle ( Agrostemma githago L.)

Abstract

Summary The metabolism and behaviour of the root applied xenobiotic [U-14C] 4-nitrophenol was studied in intact, aseptically grown plants of wheat (Triticum aestivum L.), soybean (Glycine max L.), wild oat (Avena fatua L.), and corn cockle (Agrostemma githago L.). After 7 days of exposition, different portions of the applied radioactivity were found absorbed into the plants: wild oat, 11.4%; corn cockle, 16.9%; wheat, 18.2 %; soybean, 47.8 %. Complementary long-term experiments performed only with wild oat and corn cockle showed that the uptake continued, and after 28 days of exposition, 14C portions found in the plants were 24.7% and 19.9%, respectively. In all species studied, the main percentages of absorbed radioactivity were confined to the roots (>75 % after 7 days of incubation). After 28 days, however, considerable portions of C were translocated to the aerial parts of wild oat (43.6% of absorbed 14C) and corn cockle (57.9 %). 4-Nitrophenol was almost quantitatively transformed by all plant species examined to polar soluble conjugates, besides minor amounts of non-extractable residues (wild oat: 13.2 % after 1 day, corn cockle: 2.0 % after 28 days). The primary conjugate was 4-nitrophenyl-β-D-glucoside, which was identified by TLC and HPLC. In the two monocotyledonous species, this product was partially further conjugated to 4-nitrophenyl-β-D-gentiobioside, and an unidentified 4-nitrophenyl-(1→4)-diglucoside. Additionally, the 6′-O-malonylated β-glucoside was formed in wheat. In both dicotyledonous species, the β-glucoside was in part found to be 6′-O-esterified with malonic acid.