Cupric stress induces oxidative damage marked by accumulation of H <sub>2</sub> O <sub>2</sub> and changes to chloroplast ultrastructure in primary leaves of beans ( <i>Phaseolus vulgaris</i> L.)
2010
Bouazizi, Houda | Jouili, Hager | Geitmann, Anja | Ferjani, Ezzeddine
The effect of copper excess (CuSO <sub>4</sub>) on lipid peroxidation, H <sub>2</sub> O <sub>2</sub> 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 <sup>2+</sup> at various concentrations (50 and 75 μM) for 3 days. Excess of copper significantly increased malondialdehyde content and endogenous H <sub>2</sub> O <sub>2</sub> . 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 <sub>4</sub> resulted in an increase of enzyme activity. On the contrary, CAT (catalase, EC 1.11.1.6) activity was stimulated at 50 μM CuSO <sub>4</sub> but unaltered at 75 μM CuSO <sub>4</sub> . 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.
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