Effects of cadmium on growth and antioxidant responses in Glycyrrhiza uralensis seedlings

In the present study, Glycyrrhiza uralensis (Leguminosae) seeds were germinated and grown with different concentrations (0, 0.05, 0.1, 0.2 and 0.4 mmol/l) of cadmium acetate, in order to investigate the effects of cadmium on the growth, uptake, superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) activities in Glycyrrhiza uralensis seedlings. Uptake of Cd in different tissues of seedlings increased with increasing Cd concentrations in the tested medium, with most accumulation in the radicles. Results suggested that increased cadmium concentrations lead to decreased shoot elongation and seedling biomass. SOD activity in the cotyledons, hypocotyls and radicles increased gradually up to 0.2, 0.1 and 0.4 mmol/l, respectively. POD activity in the cotyledons, hypocotyls and radicles concentrations increased continuously with rising cadmium concentrations up to 0.2, 0.1 and 0.1 mmol/l, respectively. CAT activity in the cotyledons, hypocotyls and radicles increased gradually with increasing cadmium concentrations up to 0.2, 0.2 and 0.1 mmol/l, respectively. PPO activity showed significant increases in the cotyledons, hypocotyls and radicles at 0.4, 0.1 and 0.2 mmol/l cadmium, respectively. A significant change of PAL activity in the cotyledons, hypocotyls and radicles was observed with increasing cadmium concentrations up to 0.2, 0.4 and 0.2 mmol/l, respectively. Results of POD isoenzymes suggested that the staining intensities of isoform patterns were consistent with the changes of the activities assayed in solutions. These results suggested that Glycyrrhiza uralensis seedlings may have a better protection against oxidative stress by increasing antioxidant enzymes and PAL activity exposed to cadmium toxicity.