RESUMO
In the present study, impact of kinetin (KN; 10 and 100 µM) supplementation on growth, ammonium (NH(4)(+)) assimilation and antioxidant system in pea under hexavalent chromium toxicity (Cr VI; 50, 100 and 250 µM) was investigated. Chromium decreased growth, protein, and nitrogen, and activity of glutamine synthetase (GS) and glutamate synthase (GOGAT) while it increased NH(4)(+) content and activity of glutamate dehydrogenase (GDH). Kinetin at 100 µM decreased growth and NH(4)(+) assimilation, and together with Cr, it increased Cr toxicity. Chromium and 100 µM KN increased superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities while decreasing activities of catalase (CAT), glutathione reductase (GR) and dehydroascorbate reductase (DHAR). Ascorbate and glutathione levels were decreased by Cr and 100 µM KN. In contrast, supplementation of 10 µM KN under Cr (VI) toxicity, protected NH(4)(+) assimilation and promoted growth of pea by increasing levels of some of the antioxidants i.e., CAT, GR, DHAR, ascorbate and glutathione. Results showed that 10 µM KN increases Cr tolerance while 100 µM KN exhibited opposite responses. These results could contribute to an understanding of the mechanisms of KN-mediated dual influence on metal tolerance in crop plants.