The behavior of heavy metals in relation to their influence on the common bean (Phaseolus vulgaris) symbiosis

Heavy metals (HMs) concentration is continuously increasing in agricultural soils, mainly through anthropogenic activities. Among HMs, cadmium (Cd), lead (Pb), and nickel (Ni) have shown more hazardous effects on living organs by bioaccumulation throughout the food chain. A pot experiment was arranged as a completely randomized factorial design with four replications to investigate the effects of Cd, Pb, and Ni on biological, physiological, and biochemical responses of common bean (Phaseolus vulgaris). The present study results revealed that Cd, Pb, and Ni effects on biological, physiological, and biochemical characteristics of common bean include root and shoot dry weight, shoot to root ratio, pod number, root and shoot nitrogen content, nodule number, nodule dry weight, photosynthesis pigments, leaf greenness (SPAD), DPPH scavenging, the activity of guaiacol peroxidase (POD), superoxide dismutase (SOD), ascorbate (APX), and Catalase (CAT). HMs toxicity caused a significant decrease in root and shoot dry weight, shoot to root ratio, pod number, root and shoot nitrogen content, nodule number, nodule dry weight, and intensively decreased by increasing HMs concentration in soil. HMs toxicity also decreased photosynthesis pigments and leaf greenness (SPAD). Moreover, biochemical characteristics include DPPH scavenging, POD, SOD, APX, and CAT activities improved by increasing HMs concentration. The findings also revealed that the highest adverse effects on common bean's biological, physiological, and biochemical characteristics were observed at Cd treatments compared to Pb and Ni. BCF, BAC, TF, and TE% for Cd and Ni showed a negative relationship with their concentration in soil. However, TF and TE% were improved by increasing Pb concentration in soil. Therefore, a common bean restricts the absorption and translocation of Cd, Pb, and Ni in highly polluted soil to avoid the toxic effects of Cd and Ni.