title: Exogenous application of calcium and silica alleviates cadmium toxicity by suppressing oxidative damage in rice seedlings.
abstract: The present study was undertaken to examine the possible roles of calcium (Ca(2+)) and silica (Si) in protection against oxidative damage due to Cd(2+) toxicity in rice (Oryza sativa L.) seedlings grown in hydroponics. Rice seedlings raised for 12 days in hydroponics containing Cd(NO3)2 (75 μM) showed reduced growth; increase in the level of reactive oxygen species (ROS) (O2 (·-) and H2O2), thiobarbituric acid reactive substances (TBARSs) and protein carbonylation; and increase in the activity of antioxidant enzymes-superoxide dismutase (SOD), catalase (CAT) and guaiacol peroxidase (GPX) compared to untreated controls. Exogenously added Ca(2+) (2 mM) and Si (200 μM) significantly alleviated negative effect of Cd(2+) by restoration of growth of the seedlings, suppression of Cd(2+) uptake and restoration of root plasma membrane integrity. The levels of O2 (·-), H2O2, lipid peroxidation and protein carbonyls were much lower when Ca(2+) and Si were added in the growth medium along with Cd(2+) as compared to Cd-alone-treated seedlings. Ca(2+) and Si lowered Cd-induced increase in SOD, GPX and APX activities while they elevated Cd-induced decline in CAT activity. Using histochemical staining of O2 (·-) and H2O2 in leaf tissues, it was further confirmed that added Ca(2+) and Si suppressed Cd-induced accumulation of O2 (·-) and H2O2 in the leaves. The results suggest that exogenous application of Ca(2+) and Si appears to be advantageous for rice plants in alleviating Cd(2+) toxicity effects by reducing Cd(2+) uptake, decreasing ROS production and suppressing oxidative damage. The observations indicate that Ca(2+) and Si treatments can help in reducing Cd(2+) toxicity in rice plants.
authors.affiliation: Department of Biochemistry, Faculty of Science, Banaras Hindu University, Varanasi, 221005, India.
authors.forename: Rajneesh Kumar
authors.initials: RK
authors.lastname: Srivastava
authors.forename: Poonam
authors.initials: P
authors.lastname: Pandey
authors.forename: Ritika
authors.initials: R
authors.lastname: Rajpoot
authors.forename: Anjana
authors.initials: A
authors.lastname: Rani
authors.forename: Arti
authors.initials: A
authors.lastname: Gautam
authors.forename: R S
authors.initials: RS
authors.lastname: Dubey
mesh_terms: D002104:Cadmium / Q000633:toxicity*; D002118:Calcium / Q000494:pharmacology*; D012275:Oryza / Q000187:drug effects / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D036226:Seedlings / Q000187:drug effects / Q000378:metabolism; D012822:Silicon Dioxide / Q000494:pharmacology*
chemical_list: D002104:Cadmium; D012822:Silicon Dioxide; D002118:Calcium