Salicylic acid promotes growth and affects cadmium accumulation of Cyphomandra betacea seedlings

To reduce the cadmium (Cd) uptake in fruit tree Cyphomandra betacea Sendt., the effects of different salicylic acid (SA) concentrations (0, 100, 150, 200, and 250 mg L−1) on the physiological and Cd accumulation characteristics of hydroponically grown C. betacea seedlings under Cd stress were studied. Under SA concentrations of 150, 200, and 250 mg L−1, the biomass, photosynthetic pigments (chlorophyll a, chlorophyll b, and carotenoid) contents as well as the photosynthetic parameters (net photosynthetic rate, transpiration rate, stomatal conductance, and intercellular CO2 concentration) of C. betacea seedlings were significantly higher than that of the control. The superoxide dismutase and catalase activities of C. betacea seedlings first increased and then decreased with increasing SA concentration, while the peroxidase activity and soluble protein content followed the opposite trend. When SA was applied at concentrations of 100, 150, and 200 mg L−1, the Cd contents in C. betacea seedlings were lower than in the control, whereas 250 mg L−1 SA increased C. betacea seedlings Cd contents. Taken together, the results of this experiment indicate that the biomass and Cd contents of C. betacea seedlings respectively reached a maximum and minimum under the action of SA at 150 mg L−1, a concentration thus beneficial for cultivating C. betacea seedlings under Cd stress.