The present study was aimed to reveal the effect of cadmium (Cd)-polluted soil on the activation of antioxidant enzymes, photosynthesis, pigments, water relation, and other biochemical traits and comparative effect of synthetic and organic chelators. A pot experiment was conducted using two maize varieties grown in Cd-contaminated (15 and 30 mg kg-1) soil and chelators (1 mM EDTA, and 1 mM citric acid). Cd decreased biomass and photosynthetic traits while increased malondialdehyde (MDA) contents, total proteins, and antioxidant enzyme activities. Addition of EDTA enhanced Cd uptake, antioxidative enzyme, and total proteins; however, it reduced the water, osmotic, and turgor potential as compared to Cd alone. Addition of citric acid has lessened the antioxidant enzyme activities and MDA contents and enhanced the plant biomass as compared to Cd alone. Increases in antioxidants and MDA content were found to be positively related to the Cd contents in shoot and root. The application of citric acid significantly alleviated the Cd-induced toxic effects, showing remarkable improvement in biomass. These results indicated that EDTA was more effective for mobilizing Cd from soil to the root and shoot than citric acid; however, the physiological traits and plant biomass were more strongly inhibited by EDTA than by the Cd. Our study implies that citric acid ameliorated the negative effect of Cd on physiological traits and biomass, and hence could be used effectively for Cd phytoextraction.
Keywords: Antioxidants; Cadmium; Citric acid; EDTA; Lipid peroxidation; Photosynthesis.