Determination of oxidative stress in wheat leaves as influenced by boron toxicity and NaCl stress

Boron (B) toxicity symptoms are visible in the form of necrotic spots and may worsen the oxidative stress caused by salinity. Hence, the interactive effects of combined salinity and B toxicity stress on anti-oxidative activities (TAC, LUPO, SOSA, CAT, and GR) were investigated by novel luminescence assays and standard photometric procedures. Wheat plants grown under hydroponic conditions were treated with 2.5 mu M H3BO3 (control), 75 mM NaCl, 200 mu M H3BO3, or 75 mM NaCl + 200 mu M H3BO3, and analysed 6 weeks after germination. Shoot fresh weight (FVV), shoot dry weight (DW), and relative water content (RWC) were significantly reduced, whereas the antioxidative activity of all enzymes was increased under salinity compared with the control. High B application led to necrotic leaf spots but did not influence growth parameters. Following NaCl + B treatment, shoot DW, RWC, SOSA, GR, and CAT activities remained the same compared with NaCI alone, whereas the TAC and LUPO activities were increased under the combined stress compared with NaCl alone. However, shoot FVV was significantly reduced under NaCI + B compared with NaCI alone, as an additive effect of combined stress. Thus, we found an adjustment of antioxidative enzyme activity to the interactive effects of NaCI and high B. The stress factor salt mainly produced more oxidative stress than that of the factor high B. Furthermore, addition of higher B in the presence of NaCI increases TAC and LUPO demonstrating that increased LUPO activity is an important physiological response in wheat plants against multiple stresses. (C) 2012 Elsevier Masson SAS. All rights reserved.