Exogenous Peroxidase Mitigates Cadmium Toxicity, Enhances Rhizobial Population and Lowers Root Knot Formation in Rice Seedlings

摘要

Soil cadmium (Cd) causes toxicity and oxidative stress, alters biochemical processes and rootknot formation in rice. Irrigation of exogenous peroxidase (POX) together with its co-substrate H2O2(POXRice + H2O2), is likely to have protective effect upon the biochemical and nodular changes in ricegrown in Cd-rich soil. Exposure to Cd concentration of 1.00 mg/L increased oxidative stress, loss of cellviability, electrolyte leakage and root knot formation, whereas it significantly lowered the chlorophyll leveland rhizobium growth in rice. Irrigation of exogenous POXRice + H2O2 to Cd-stressed rice seedlingsreversed the Cd-induced alterations in rice to levels similar in control (non-stressed) seedlings. Resultsprovided strong evidence of exogenous POXRice + H2O2-mediated reversal and restoration of physiologicaland biochemical processes as well as increased resistance of rice seedlings to root knot formation.Irrigation with POXRice + H2O2 appeared to contribute towards bringing normoxic conditions in the otherwisehypoxic soil environment by enhancing the O2 in pot-experiments due to reduced Cd uptake, enhancedmineral homeostasis of essential elements viz. P, Fe, Mo, Mg and Mn for maintenance of root architecturedamaged by lipid peroxidation and reduction in oxidative stress by reducing Cd-induced reactive oxygenspecies generation. Therefore, the mitigation of Cd-toxicity in rice through this novel approach appeared tobe a promising mode to limit Cd-uptake, modulate protective and tolerance mechanisms for sustainablerice yield in Cd-contaminated rice-croplands and prevent nematode attack in rice, however, more detailedstudies are needed prior to large scale applications.