Responses of seedling growth and antioxidant activity to excess iron and copper in Triticum aestivum L.

The purpose of this study was to analyze phytotoxicity mechanism involved in root growth and to compare physiological changes in the leaves of wheat seedlings exposed to short term iron (Fe) and copper (Cu) stresses (0, 100, 300 and 500 mu M). All applied Fe or Cu concentrations reduced root and shoot lengths, but seed germination was inhibited by Cu only at 500 mu M. Analyses using fluorescent dye 2',7'-dichlorodihydrofluorescein diacetate indicated enhanced H2O2 levels in seedling roots under Fe and Cu treatments. Cu stress at the same concentration induced a great reduction in cell viability and a strong damage on membrane lipid in the roots with respect to Fe treatment. Significant increases in the total chlorophyll (chl) content including chl a and chl b were observed in response to higher Fe concentrations, whereas the highest Cu concentration (500 mu M) led to significant decreases in the total chl content including chl a. Additionally, leaf peroxidase (POD) and ascorbate peroxidase (APX) were stimulated by Fe stress, but the highest Fe concentration exhibited inhibitory effect on leaf APX activity. In contrast, copper treatment resulted in an elevation in leaf catalase and POD activities. Therefore, H2O2 content in the leaves associated with copper was significantly lower than that with iron at the same concentration. (C) 2012 Elsevier Inc. All rights reserved.