Abstract
Heavy metal (HM) contamination causes severe detrimental effects on plant growth. Irradiated sodium alginate (ISA) has been proposed for enhancing the efficacy and selectivity of metal ion biosorption from plants under HM-toxicity. The present study has been planned to investigate the morphological, molecular, physiological, and regulation of transcript levels of defence mechanisms for alleviation of HM toxicity in Vigna radiata plants by irradiated sodium alginate (ISA). V. radiata L. plants were treated with T-0-water (control); T-Cd-CdCl2 (100 mu M); T-Pb-Pb(NO3)(2) (500 mu M); T-Fe-FeSO4 (300 mu M), and ISA solution at 75 mg/l as a foliar spray onto leaves. Our results suggested the positive impact of ISA for HM stress mitigation by V. radiata L. plants, through modulatory effects on molecular and physiological attributes. In our study, we evaluated the growth characteristics (plant height, leaf area, total fresh weight and grain weight), pigment contents, photosynthetic efficiency ((CO2)-C-14-fixation), enzyme activities (nitrate reductase, ribulose-1,5-bisphosphate-carboxylase/oxygenase, and carbonic anhydrases), and macronutrient contents (P, N, and K) in metal-stressed plants. All these attributes were found to be stimulated after ISA application. Also, ISA reduced the total malondialdehyde, free proline, and total phenol content in heavy metal-exposed plants. The transcriptional expression profiling was conducted by examining the expression levels of AtPDR12, AtATM3, AtPCR1, MPK4, MPK6, and AtPDR8 genes that inferred the ISA-mediated detoxification of HMs in V. radiata plants. The data in the present research clearly indicated that treatment with foliar sprays of ISA (75 mg/l) resulted in enhanced tolerance of V. radiata plants against different HM stresses.