ORIGINAL PAPER Effect of nitrogen deficiency on antioxidant status and Cd toxicity in rice seedlings Ya-Lin Lin • Yun-Yang Chao • Wen-Dar Huang • Ching Huei Kao Received: 30 August 2010 / Accepted: 21 January 2011 / Published online: 29 January 2011 Ó Springer Science+Business Media B.V. 2011 Abstract Effect of nitrogen (N) deficiency on antioxidant status and Cd toxicity in rice seedlings was investigated. N deficiency resulted in a reduction of shoot growth but not root growth. The contents of N-containing compounds such as nitrate, chlorophyll, and protein decreased in leaves of rice seedlings grown under N deficiency. Accumulation of abscisic acid and H 2 O 2 in leaves was induced by N defi- ciency. The content of ascorbate and the activities of ascorbate peroxidase, glutathione reductase, and catalase in N-deficient leaves were lower than their respective control leaves. However, glutathione content was not affected and superoxide dismutase activity was increased by N defi- ciency. Cd toxicity in N-deficient seedlings was more pronounced than that in N-sufficient ones. Pretreatment with ascorbate or L-galactono-1,4-lactone, a biosynthetic precursor of ascorbate resulted in a reduction of Cd toxicity enhanced by N deficiency. N deficiency also resulted in an enhancement of Cd uptake in rice seedlings. The possible mechanism of Cd toxicity enhanced by N deficiency is discussed. Keywords Antioxidant system Á Cadmium Á Nitrogen deficiency Á Rice Abbreviations ABA Abscisic acid APX Ascorbate peroxidase AsA Ascorbic acid CAT Catalase DAB 3,3-Diaminobenzidine DHA Dehydroascorbate DW Dry weight ELISA Enzyme-linked immunosorbent assay FW Fresh weight GalL L-galactono-1,4-lactone GR Glutathione reductase GSH Reduced glutathione GSSG Oxidized glutathione ROS Reactive oxygen species MDA Malondialdehyde SOD Superoxide dismutase Introduction Cadmium (Cd) is a widespread nonessential heavy metal, classified as a human carcinogen, and the uptake and accumulation of Cd in plants represent the main entry pathway into humans and mammals. In plants, Cd causes severe physiological and morphological effects such as chlorosis and growth reduction. Cd is a non-redox metal unable to participate in Fenton-type reactions, but it causes oxidative stress by generating reactive oxygen species (ROS) (Garnier et al. 2006). ROS react with lipids, pro- teins, pigments and nucleic acids and cause lipid peroxi- dation, membrane damage and inactivation of enzymes, thus resulting toxic effects. To minimize and/or to protect against the toxic effects of these damaging ROS, plants have evolved highly regulated enzymatic and non-enzy- matic mechanisms to keep a balance between ROS pro- duction and destruction in order to maintain cellular redox homeostasis. Plants use enzymes like superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), and catalase (CAT) as well as non-enzymatic Y.-L. Lin Á Y.-Y. Chao Á W.-D. Huang Á C. H. Kao (&) Department of Agronomy, National Taiwan University, Taipei, Taiwan, ROC e-mail: kaoch@ntu.edu.tw 123 Plant Growth Regul (2011) 64:263–273 DOI 10.1007/s10725-011-9567-0