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- Author or Editor: Houda Bouazizi x
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The effect of copper excess on growth, H 2 O 2 level and peroxidase activities were studied in maize shoots. Ten-day-old seedlings were cultured in nutrient solution that contained Cu 2+ ions at various concentrations (50 and 100 μM) for seven days. High concentrations of Cu 2+ ions caused significant decrease both in matter production and elongation of maize shoots. In addition, treatment with CuSO 4 increased levels of H 2 O 2 and induced changes in several peroxidase activities. Moreover, the disturbance of the physiological parameters was accompanied by the modulation of the peroxidase activities: GPX (Guaiacol peroxidase, EC 1.11.1.7), CAPX (Coniferyl alcohol peroxidase, EC 1.11.1.4) and APX (Ascorbate peroxidase, EC.1.11.1.11). Furthermore, this modulation becomes highly significant, especially, in the presence of 100 μM of CuSO 4 .
The effect of copper excess (CuSO 4 ) on lipid peroxidation, H 2 O 2 content, and antioxidative enzyme activities was studied in primary leaves of bean seedlings. Fourteen-day-old bean seedlings were cultured in a nutrient solution containing Cu 2+ at various concentrations (50 and 75 μM) for 3 days. Excess of copper significantly increased malondialdehyde content and endogenous H 2 O 2 . This radical accumulated in the intercellular spaces of palisade mesophyll cells. In addition, cupric stress induced changes in antioxidant enzyme activities. GPX (guaiacol peroxidase, EC 1.11.1.7) activity was decreased in 50 μM Cu-stressed leaves whereas 75 μM of CuSOP 4 resulted in an increase of enzyme activity. On the contrary, CAT (catalase, EC 1.11.1.6) activity was stimulated at 50 μM CuSO 4 but unaltered at 75 μM CuSO 4 . Transmission electron microscopy revealed that excess copper induced changes in the ultrastructure of chloroplasts visible in form of a deterioration in the grana structure and the accumulation and swelling of starch grains in the stroma.
We studied oxidative stress and peroxidase activity resulting from application of excess copper in the nutrient medium on the roots of young bean seedlings. The change in H 2 O 2 content, lipid peroxidation and antioxidant enzymes activities were quantified and located. Excess of copper caused a loss of membrane integrity and the formation of hydrogen peroxide (H 2 O 2 ) as visualized in the transmission electron microscopy and measured using spectrophotometry. H 2 O 2 accumulated in the intercellular spaces and in the cell wall. The production of H 2 O 2 was accompanied by an increase in the activity of soluble and ionic GPX (guaiacol peroxidase, EC 1.11.17), CAPX (coniferyl alcohol peroxidase) and NADH oxidase.
