Effects of rare earth elements on callus growth, soluble protein content, peroxidase activity and shoot differentiation of Echinacea angustifolia cultures in vitro

Abstract

The effects of lanthanum nitrate (La3+) and cerium nitrate (Ce4+) on Echinacea angustifolia callus growth and subculture were studied by the measurement of callus fresh weight, dry weight and time-course curve. The effects of La3+ on soluble protein content, peroxidase activity and shoot differentiation of callus were also investigated. Low concentrations of La3+ and Ce4+ (0.01, 0.1 and 1 mg/l) showed enhancing action on callus growth while the suppress effect was found at high concentration
treatments (10 and 100 mg/l). The result from time-course experiment indicated that La3+ or Ce4+ showed promotion on callus growth after 15 days cultured and Ce4+ displayed a better effect than La3+. Different
proportion mixture of La3+ and Ce4+ at 1 mg/l in total showed stimulating action on callus growth and the optimum proportion was the mixture of 40% La3+ and 60% Ce4+. Inhibitory effects were observed when the calli derived from the treatments with La3+ and Ce4+ were subcultured for the first generation. The dose-dependent effects of La3+ on soluble protein content, peroxidase activity and shoot differentiation were also noticed. The optimum concentration for callus growth and shoot differentiation was 0.1 mg/l and the green, loose calli with low percentage of brown callus were obtained at this concentration.