ORIGINAL PAPER Changes of antioxidants and GSH-associated enzymes in isoproturon-treated maize Mamdouh M. Nemat Alla Æ Nemat M. Hassan Received: 31 July 2006 / Revised: 17 November 2006 / Accepted: 17 November 2006 / Published online: 22 February 2007 Ó Franciszek Go ´ rski Institute of Plant Physiology, Polish Academy of Sciences, Krako ´ w 2007 Abstract The recommended field dose (RFD) of iso- proturon induced significant accumulations of H 2 O 2 in the leaves of 10-d-old maize seedlings throughout the following 20 d; the accumulation increased with time and also with herbicide dose. Meanwhile, low doses significantly increased ascorbic acid, glutathione and thiols while high doses caused diminutions. Superoxide dismutase (SOD; EC 1.15.1.1) activity was significantly enhanced up to the 12th d whereas ascorbate peroxidase (APX; EC 1.11.1.7) activity was significantly reduced after the fourth d onwards. Catalase (CAT; EC 1.11.1.6) and guaiacol peroxidase (GPX; EC 1.11.1.7) activities were similarly increased during the first 4 d but de- creased from the 12th and the eighth d, respectively. Low doses increased SOD and GPX activities but high doses led to diminutions whereas CAT and APX were reduced by all doses. The activities of c-glutamyl-cys- teine synthethase (c-GCS; EC 6.3.2.2) and glutathione synthethase (GSS; EC 6.3.2.3) were enhanced for 4 d; high doses caused general reductions. Isoproturon sig- nificantly reduced activities of glutathione S-transferase (GST; EC 2.5.1.18) isoforms [GST (CDNB) , GST (ALA) , or GST (MET) ] after the fourth d, however, it had no effect on GST (ATR) . Similar reductions in activities of gluta- thione peroxidase (GSPX; EC 1.15.1.1) and glutathione reductase (GR; EC 1.6.4.2) were detected up to the 16th and the 12th d, respectively. The activities of GST iso- forms, GSPX and GR were reduced by high doses. These changes seemed to be related and might point to an oxidative stress state that exacerbated with pro- longed time and/or increased isoproturon dose. Keywords Antioxidants Á GSH-associated enzymes Á Isoproturon Á Maize Abbreviations APX Ascorbate peroxidase AsA Ascorbate CAT Catalase CDNB 1-Chloro-2,4-dinitrobenzene d Day(s) DTNB 5,5-dithiobis-(2-nitrobenzoic acid) DTT Dithiothritol c-GCS c-Glutamylcysteine synthetase GPX Guaiacol peroxidase GR Glutathione reductase GSH Reduced glutathione GSPX Glutathione peroxidase GSS Glutathione synthetase GST Glutathione S-transferase NBT Nitroblue tetrazolium PMSF Phenyl methyl sulphonyl fluoride PVPP Polyvinylpolypyrrolidone RFD Recommended field dose ROS Reactive oxygen species SOD Superoxide dismutase TCA Trichloroacetic acid Introduction Isoproturon [arelon, 3-(4-isopropylphenyl)-1,1-dimeth- ylurea] is widely used in Egypt for pre- and post-emer- Communicated by G. Bartosz. M. M. Nemat Alla (&) Á N. M. Hassan Botany Department, Faculty of Science, Mansoura University, Damietta, Egypt e-mail: mamnematalla@mum.mans.edu.eg 123 Acta Physiol Plant (2007) 29:247–258 DOI 10.1007/s11738-007-0031-8