NaCl and CuSO4 treatments trigger distinct oxidative defence mechanisms in Nicotiana plumbaginifolia L.

To gain better insights into the generation of oxidative stress by NaCl stress, we compared the effects of toxic, sublethal concentrations of NaCl (150 mM) with those of CuSO4 (100 mu M) On the antioxidant defence responses of Nicotiana plumbaginifolia L. plants grown in hydroponic culture. Short- and long-term adaptive responses were investigated as well as the effects of root cutting to allow rapid absorption of ions. Our results show that photosynthesis is already affected after 12 h of both treatments and that photoinhibition is induced. Furthermore, the two treatments showed distinct patterns of induction of the genes of the antioxidant systems. Principally, NaCl stimulated catalase activity through activation of the Cat2 and Call genes, whereas with CuSO4, transcript levels, protein levels, and enzymatic activities of glutathione peroxidase, ascorbate peroxidase, and superoxide dismutase were differentially induced. The antioxidants ascorbate and glutathione were found to be largely oxidized after 12 h, suggesting an inability of the recycling process to cope with the stress, In addition, both NaCl and CuSO4 treatments stimulated the accumulation of the osmolyte proline, Therefore, we conclude that the uptake and accumulation of different types of ions lead to the generation of distinct antioxidant responses in N. plumbaginifolia.