Abstract
The present study evaluated the effects of exogenous hemin on cadmium toxicity in terms of metal accretion and stress resilience in Vigna radiata L. (Wilczek). One-week-old seedlings were treated with CdCl2 (50 μM) alone and in combination with hemin (0.5 mM) in half-strength Hoagland medium for 96 h. The optimum concentrations of Cd and hemin were determined on the basis of haem oxygenase-1 activity. The results demonstrated that under Cd stress, plants accumulated a considerable amount of metal in their tissues, and the accumulation was higher in roots than in leaves, which significantly reduced the plant biomass and chlorophyll content by increasing the oxidative stress (MDA and H2O2 content). However, hemin supplementation under Cd,-stress improved plant growth by enhancing the harvestable biomass and photosynthetic pigments, increasing antioxidant activities (SOD, APX, POD, HO-1 and proline), lowering oxidative damage and increasing Cd tolerance in plants. Furthermore, the application of hemin enhances the removal efficiency of Cd in V. radiata by increasing the uptake of Cd via roots and its translocation from roots to foliar tissues. Thus, the study suggests that hemin has the potential to improve the stress tolerance and phytoremediation ability of heavy metal-tolerant plants so that they can be used instead of hyperaccumulators for remediation of Cd-contaminated environments.
Highlights
The present study evaluated the effects of exogenous hemin on cadmium toxicity in terms of metal accretion and stress resilience in Vigna radiata L. (Wilczek)
Since hemin acts as haem, it greatly enhances the catalysis of the haem oxygenase-1 enzyme by overexpressing its mRNA and increasing protein abundance; hemin is regarded as a proficient activator of haem oxygenase-1 that exerts protective effects against various abiotic stresses in an enzyme-dependent m anner[5]
The length and biomass of V. radiata seedlings were studied to evaluate the adverse impact of cadmium on crops and the role of hemin against Cd toxicity
Summary
The present study evaluated the effects of exogenous hemin on cadmium toxicity in terms of metal accretion and stress resilience in Vigna radiata L. (Wilczek). The present study evaluated the effects of exogenous hemin on cadmium toxicity in terms of metal accretion and stress resilience in Vigna radiata L. The study suggests that hemin has the potential to improve the stress tolerance and phytoremediation ability of heavy metal-tolerant plants so that they can be used instead of hyperaccumulators for remediation of Cd-contaminated environments. Several chemical reagents and bioregulators, such as ethylene, melatonin, nitric oxide and plant growth regulators (PGRs), are known to enhance Cd stress tolerance by modulating various physiochemical processes that improve crop biomass and further stimulate the uptake and translocation of heavy metals[2,8,9]. It is possible to implicate hemin as an effective and efficient biostimulator to improve the phytoremediation potential of heavy metal-tolerant plants. The aims of the present work were (1) to investigate the effect of exogenous hemin on the biomass production and chlorophyll content of V. radiata; (2) to analyse the mechanism by which hemin affects Cd tolerance of V. radiata; and (3) to verify the influence of exogenous hemin in improving the Cd phytoremediation efficiency of V. radiata
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