NaCl protects against Cd and Cu-induced toxicity in the halophyte Atriplex halimus

The objective of the present work was to evaluate the extent of Cd- and Cu-induced oxidative stress and the antioxidant response triggered in the halophyte species Atriplex halimus after metallic trace elements exposure. Plants were treated for one month with Cd2+ or Cu2+ (400 mu M) in the absence or presence of 200 mM NaCl in the irrigation solution. The interaction between salinity and heavy metal stress was analyzed in relation to plant growth, tissue ion contents (Na+, K+ and Mg2+), oxidative damage and antioxidative metabolism. Data indicate that shoot and root weight significantly decreased as a consequence of Cd2+- or Cu2+-induced stress. Metallic stress leads to unbalanced nutrient uptake by reducing the translocation of K+ and Mg2+ from the root to the shoot. The levels of malondialdehyde increased in root tissue when Cd, and especially Cu, were added to the irrigation solution, indicating that oxidative damage occurred. Results showed that NaCl gave a partial protection against Cd and Cu induced toxicity, although these contaminants had distinct influence on plant physiology. It can be concluded that salinity drastically modified heavy metal absorption and improved plant growth. Salinity also decreased oxidative damage, but differently in plants exposed to Cd or Cu stress.