ORIGINAL ARTICLE Temporal changes in the growth, saponin content and antioxidant defense in the adventitious roots of Panax ginseng subjected to nitric oxide elicitation Rajesh Kumar Tewari Soo Yeon Lee Eun Joo Hahn Kee Yoeup Paek Received: 27 July 2007 / Accepted: 11 September 2007 / Published online: 30 October 2007 Ó Korean Society for Plant Biotechnology and Springer 2007 Abstract Nitric oxide (NO) is a diffusible, gaseous signaling molecule. In plants, NO influences growth and development, and it can also affect plant responses to various stresses. Because NO induces root differentiation and interacts with reactive oxygen species, we examined the temporal effect of NO elicitation on root growth, saponin accumulation and antioxidant defense responses in the adventitious roots of mountain ginseng (Panax ginseng). The observations revealed that NO is involved in root growth and saponin production. Elicitation with sodium nitroprusside (SNP) activated O 2 – -generating NADPH oxidase (NOX) activity, which most probably subsequently enhanced growth of adventitious roots of mountain ginseng. A severe inhibition of NOX activity and decline in dry weight of SNP elicited adventitious roots in the presence of NOX inhibitor (diphenyl iodonium, DPI), which further supports involvement of NOX in root growth. Enhanced activities of antioxidant enzymes by SNP appear to be responsible for low H 2 O 2 , less lipid peroxidation, and modulation of ascorbate and non-protein thiol statuses in the adventitious roots of mountain ginseng. Dry mass, saponin content and NOX activity was related with NO content present in adventitious roots of mountain ginseng. Keywords Antioxidants  Antioxidant enzymes  NADPH oxidase  Root growth  Reactive oxygen species Abbreviations APX Ascorbate peroxidase AsA Ascorbic acid CAT Catalase DHA Dehydroascorbate DHAR DHA reductase DTT Dithiothreitol EDTA Ethylenediamine tetraacetic acid GR Glutathione reductase MDA Malondialdehyde NOX NADPH oxidase POD Peroxidase ROS Reactive oxygen species SNP Sodium nitroprusside SOD Superoxide dismutase TCA Trichloroacetic acid XTT 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)- 2H-tetrazolium-5-carboxanilide sodium salt Introduction Nitric oxide (NO) is a small diffusible, ubiquitous, gaseous bioactive molecule, which participates in the broad spectrum of pathophysiological and developmental processes of living beings (Lamattina et al. 2003). NO simultaneously acts on several biochemical aspects through the modulation of the cellular redox status and cytosolic calcium ion (Ca 2+ ) concentrations. NO is an interesting signaling molecule having homeostatic properties for the coordination and R. K. Tewari  E. J. Hahn  K. Y. Paek (&) Research Center for the Development of Advanced Horticultural Technology, Chungbuk National University, Cheongju 361-763, Republic of Korea e-mail: paekky@chungbuk.ac.kr R. K. Tewari e-mail: rktewari_bot@yahoo.com S. Y. Lee CBN Biotech, Chungbuk National University, Cheongju 361-763, Republic of Korea 123 Plant Biotechnol Rep (2007) 1:227–235 DOI 10.1007/s11816-007-0036-1