Immediate response of Chara braunii exposed to zinc and hydrogen peroxide

Abstract

The immediate effect of zinc (Zn) and hydrogen peroxide (H2O2) in Chara braunii was analyzed in short‐time exposure experiments. The exposure concentrations were 12.3, 18.4, and 24.5 μmol L−1 H2O2, 12, 60, and 120 mg L−1 Zn, and 12.3 μmol L−1 H2O2 + 12 mg L−1 Zn, 12.3 μmol L−1 H2O2 + 60 mg L−1 Zn, and 18.4 μmol L−1 H2O2 + 12 mg L−1 Zn. The stress response of C. braunii was analyzed by measuring photosynthetic photosystem II activity, chlorophyll a and b and carotenoid contents, the H2O2 concentration, and antioxidant enzyme activities of ascorbic peroxidase, catalase, and guaiacol peroxidase. The short‐term addition of Zn reduced pigment contents in C. braunii. Chlorophyll a and b and carotenoid contents in H2O2‐exposed C. braunii were as high as in control plants. Photosynthesis was reduced in H2O2‐treated C. braunii and the short‐term addition of Zn did not affect the electron transport rate. H2O2 concentration and antioxidant enzyme activities in C. braunii were not significantly different between control and exposed plants. Trends of enzymatic adaptation were described: the H2O2‐induced stress response was characterized by increased antioxidant enzyme activities, whereas Zn inactivated catalase in C. braunii.