the impact of different concentrations of cadmium and arsenic in soil on the growth, some biochemical and physiological properties in lemon balm (melissa officinalis l.)

Heavy metal toxicity such as cadmium (cd) and arsenic (as) are two non-essential elements, toxic, tend to uptake and translocate within plant tissues. in a pot experiment by using factorial design with three replicates, four concentrations (as1 = 0, as2 = 10, as3 = 20, and as4 = 30 mg as kg⁻¹ in the soil) of sodium arsenate (nah2as4o.7h2o) were investigated on lemon balm plants. additionally, four concentrations (cd1 = 0, cd2 = 10, cd3 = 20, and cd4 = 30 mg cd kg⁻¹ in the soil) of cadmium sulfate (cdso4) were tested. cd and as each alone, decreased (50.7%) shoot dry weight. by increasing the concentrations from 0 to 30 mg kg⁻¹, cd (18.5%) and as (32.01%) reduced root dry weight. both metals significantly reduced the concentrations of chlorophyll “a” (72.2%) and carotenoids (71.6%), while simultaneously increased anthocyanin (77.6%) in the leaves. cd and as induced considerable oxidative stress, reflected by a 49.4% increase in catalase (cat) activity and a 49.6% increase in superoxide dismutase (sod) activity in the leaves. furthermore, the concentrations of mineral elements such as nitrogen, phosphorus, and potassium were diminished in the leaves due to the toxicity of cd and as. the concentration of cd in the roots varied from 2.7 to 53.3 mg kg⁻¹ dry weight (19.5 fold increase), while in the shoot, it was increased by 1.5 times. for the concentration of as in the roots, it was elevated by 17.9 times, and in the shoot, it was increased by 15.1 times. in lemon balm, a greater quantity of as compared to cd was translocated to the aerial parts. as toxicity had a more substantial effect on plant shoot growth relative to cd.