Accumulation, subcellular localization and ecophysiological responses to copper stress in two Daucus carota L. populations
Copper accumulation, subcellular localization and ecophysiological responses to excess copper were investigated using pot culture experiments with two Daucus carota L. populations, from a copper mine and an uncontaminated field site, respectively. Significant differences of malondialdehyde (MDA) and hydrogen peroxide (H2O2) concentrations and antioxidant enzyme [superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX)] activities of leaves under Cu treatment were observed between the two populations. At high Cu concentrations (400 and 800 mg kg−1), a significant increase in contents of MDA and H2O2 but a significant decrease in activities of SOD, CAT and APX were observed in uncontaminated population. Contrarily, the population from copper mine maintained a lower level of MDA and H2O2 but higher activities of SOD, CAT and APX. Copper accumulation in roots and shoots increased significantly with the increase of copper concentrations in soils in the two populations. No significant difference of the total Cu in roots and shoots was found between the two populations at same copper treatment. There were also no striking differences of cell wall-bound Cu and protoplasts Cu of leaves between the two populations. The difference was that Cu concentration in vacuoles of leaves was 1.5-fold higher in contaminated site (CS) population than in uncontaminated site population. Hence, more efficient vacuolar sequestration for Cu and maintaining high activities of SOD, CAT and APX in the CS population played an important role in maintaining high Cu tolerance.
KeywordsAntioxidant enzymes Copper subcellular localization Cu resistance Daucus carota L. Lipid peroxidation
We thanked Dr Qingchun Zhou, Dr Xiangzhen Li (University of Oklahoma, Norman, OK, USA) and my colleague Dr Yongqin Chen for providing help.
This research was funded by the National Natural Science Foundation of China (Project 20477032) and Natural Science Foundation of Zhejiang Province (Y504256).
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