Stimulating the efficiency of Cd-phytoremediation from contaminated soils by Solanum nigrum L.: Effect of foliar and soil application of yeast extract

Abstract

Black nightshade (Solanum nigrum L.) is an annual grass and is known as a Cd-hyperaccumulator. The current study aims to use a natural biostimulant, i.e., yeast extract, to improve the phytoremediation capacity of S. nigrum in a pot experiment. S. nigrum was cultivated in a Cd-contaminated soil and treated with yeast extract (20% w/v) via soil or foliar application. The experiment included four treatments: control (C), yeast extract applied via soil (S), yeast extract applied via foliar spraying (F), and yeast extract applied via soil and foliar application (SF). The treatments of yeast extract were laid out in a completely randomized design (CRD) with six replicates. The plants of S. nigrum sprayed with yeast extract in combination with soil addition had the highest significant values of Cd in the plant shoot. The addition of yeast extract significantly increased the phytoremediation indexes compared to the control. The addition of yeast extract to the soil or via foliar spraying significantly enhanced the translocation factor (TF) and bioaccumulation factor (BAF) of Cd in S. nigrum plants. The combined addition of soil and foliar spraying of yeast extract (SF) was more effective than the sole addition of S or F in increasing the TF and BAF of Cd by S. nigrum. The addition of SF increased both the TF and BAF by 50% above the control. The yeast extract significantly enhanced the activity of superoxide dismutase (SOD) and peroxidase (POD). The combined addition of SF was more effective in enhancing the concentrations of proline and soluble carbohydrates in the plant leaves than the sole addition of each treatment. The maximum nutrient uptake and photosynthesis pigments, i. e., chlorophyll, were achieved from the addition of yeast extract to the soil in combination with foliar spraying. The yeast extract improved S. nigrum's Cd-phytoextraction capacity by protecting photosynthesis pigments and increasing antioxidant defenses and plant nutrient uptake. S. nigrum plants have many characteristics that qualify them for use in cleaning Cd-contaminated soils. However, it is recommended that yeast extract be sprinkled on the leaves and added directly to the soil to improve phytoremediation efficiency.