Growth, antioxidant enzyme activities and some physiological properties of lemon balm (Mellissa officinallis L.) in response to arsenic and cadmium stress

Abstract

Arsenic (As) and cadmium (Cd) are nonessential elements, toxicants and inhibit various physiological and biochemical processes in plants. The aim of this experiment was to investigate the effect of four concentrations of sodium arsenate (NaH2As4O. 7H2O): As1 = 0, As2 = 10, As3 = 20, and As4 = 30 mg As kg− 1 soil and cadmium sulfate (CdSO4): Cd1 = 0, Cd2 = 10, Cd3 = 20 and Cd4 = 30 mg Cd kg− 1 in soil on root and shoot growth, nutrient uptake and activity of some antioxidant enzymes in lemon balm plant. By increasing Cd and As concentration from 0 to 30 mg kg− 1 in soil, the dry weight of aerial part 50.7% decreased. This reduction for dry weight of roots in Cd treatment was 18.5%, and in As treatment was 32.01%. Cd and As decreased the concentration of chlorophyll “a” and carotenoid and increased the concentration of anthocyanin (77.6%) in the leaves. The activity of antioxidant enzymes such as catalase (CAT): 49.4% and superoxide dismutase (SOD): 49.6% increased. Cd and As also decreased the concentration of nitrogen, phosphorus and potassium in leaves of lemon balm plant. The concentration of Cd in the root reaches from 2.72 to 53.3 µg g dry weight) an increase of about 19.5 times). And in the aerial part it was an increase of about 1.5 times. The concentration of As in the root reached from 1.52 to 27.3 µg g dry weight (an increase of 17.9 times) and in the aerial part it was 15.1 times. Due to the transfer a large amount of As compared to Cd to the aerial part, It can be concluded that the effect of As on this plant was greater than that of Cd.