Phytotoxic Effects of Residual Glufosinate on the Nitrogen Assimilation of Transplanted Rapeseed Seedlings

Abstract

ABSTRACTHerbicide application is an efficient method to control weed growth in modern agriculture production, but there is concern about the ecological impact of unwanted herbicide residues in the soil. Rapeseed varieties ZS11 and D148 were used to evaluate the phytotoxic effects of residual glufosinate on the assimilation of nitrogen (N) in rapeseed seedlings transplanted to untreated [0 g hm−2 glufosinate] or treated [450 g hm−2 and 900 g hm−2 glufosinate] soils. Glutamine synthetase (GS) and glutamate dehydrogenase (GDH) activities, the contents of ammonium (NH4+), free amino acids (FAA), and soluble protein (SP), and seedling dry weight (DW) were determined at 5, 8, 11, 20, 40, and 70 d post-transplant. Both concentrations of glufosinate induced physiological phytotoxicity on the N assimilation of transplanted seedlings of both varieties, as their leaves and roots presented reduced GS activities and SP contents, and increased GDH activities, and NH4+ and FAA content. Glufosinate phytotoxicity on the N assimilation of transplanted seedlings reached a plateau at 11 to 20 d. further, GDH in roots and GS in leaves were still significantly different at 70 d. Meanwhile, ZS11 might be more sensitive to glufosinate than D148 since ZS11 had more variation than D148 at the same treatment, and the overdose of glufosinate more strongly inhibited N assimilation than the recommended dose. Therefore, it is essential to apply a suitable glufosinate dose to the transplanted variety, to minimize adverse effects on crops and the environment.Abbreviations: N, Nitrogen; GS, Glutamine synthetase; GDH, glutamate dehydrogenase; NH4+, ammonium; FAA, free amino acids; SP, soluble proteins; DW, Dry weight; ANOVA, one-way analysis of variance; NO3−, nitrate; OECD, Organisation for Economic Co-operation and Development; PPT, phosphinothricin; USEPA, United States Environmental Protection Agency