title: Effect of magnesium deficiency on antioxidant status and cadmium toxicity in rice seedlings.
abstract: Cadmium (Cd) is one of the most toxic heavy metals and inhibits physiological processes of plants. Magnesium (Mg) is known as one of the essential nutrients for plants. Mg deficiency in plants affects metabolic processes. Plants grown in the field may encounter several abiotic stresses, rather than a single stress. Thus, the relationship between Mg nutrition and Cd toxicity is of ecological importance. In this study, effects of Mg deficiency on antioxidant systems and Cd toxicity in rice seedlings were investigated. Mg deficiency significantly decreased Mg concentrations in shoot and roots of rice seedlings. However, fresh weight and dry weight of rice seedlings were not affected by Mg deficiency. The contents of ascorbate and glutathione (GSH), the ratio of GSH/oxidized glutathione, and the activities of superoxide dismutase, ascorbate peroxidase, glutathione reductase, and catalase in Mg-deficient leaves were higher than respective control leaves. Cd toxicity was judged by the decrease in biomass production, decrease in chlorophyll, and induction of oxidative stress. Based on these criteria, we demonstrated that Mg deficiency protected rice seedlings from Cd stress. Moreover, chlorophyll destruction by paraquat was higher in detached leaves from Mg-sufficient than Mg-deficient seedlings. Cd concentration was higher in Mg-deficient shoot and roots than their respective control shoot and roots, suggesting that the protective effect of Mg deficiency against Cd toxicity is not due to reduction of Cd uptake. Moreover, we observed that Cd-decreased Fe and Zn contents in Mg-deficient seedlings were more pronounced than that in Mg-sufficient seedlings. Of particular interest is the finding that the increase in OsIRT1, OsZIP1, and OsZIP3 transcripts caused by Cd in Mg-deficient roots was greater than that in control roots.
authors.affiliation: Department of Agronomy, National Taiwan University, Taipei, Taiwan, ROC.
authors.forename: Ting-Shao
authors.initials: TS
authors.lastname: Chou
authors.forename: Yun-Yang
authors.initials: YY
authors.lastname: Chao
authors.forename: Wen-Dar
authors.initials: WD
authors.lastname: Huang
authors.forename: Chwan-Yang
authors.initials: CY
authors.lastname: Hong
authors.forename: Ching Huei
authors.initials: CH
authors.lastname: Kao
mesh_terms: D000975:Antioxidants / Q000032:analysis / Q000378:metabolism*; D060387:Ascorbate Peroxidases / Q000378:metabolism; D001205:Ascorbic Acid / Q000378:metabolism; D018533:Biomass; D002104:Cadmium / Q000032:analysis / Q000378:metabolism / Q000633:toxicity*; D002374:Catalase / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D005980:Glutathione Reductase / Q000378:metabolism; D018527:Hydroponics; D007501:Iron / Q000378:metabolism; D008274:Magnesium / Q000032:analysis / Q000378:metabolism*; D012275:Oryza / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism; D013997:Time Factors; D015032:Zinc / Q000378:metabolism
chemical_list: D000975:Antioxidants; D002104:Cadmium; D002734:Chlorophyll; D007501:Iron; D060387:Ascorbate Peroxidases; D002374:Catalase; D013482:Superoxide Dismutase; D005980:Glutathione Reductase; D005978:Glutathione; D008274:Magnesium; D015032:Zinc; D001205:Ascorbic Acid