ORIGINAL PAPER Effects of brassinosteroids on barley root growth, antioxidant system and cell division Gonul Kartal Æ Aslihan Temel Æ Ercan Arican Æ Nermin Gozukirmizi Received: 17 January 2008 / Accepted: 26 March 2009 / Published online: 7 April 2009 Ó Springer Science+Business Media B.V. 2009 Abstract Homobrassinolide (HBR), which is one of the most biologically active forms of Brassinosteroids (BRs), was used to examine the potential effects of hormone on root germination, antioxidant system enzymes and cell division of barley (Hordeum vulgare L.). Seeds were ger- minated between filter papers in 0.1, 0.5 and 1.0 lM HBR- supplemented distilled water for 48 h at dark with their controls. HBR application increased especially the primary root growth significantly with increasing concentrations when compared with the control materials and reached two fold increase in 1.0 lM HBR treated material. Treated and untreated control group roots were fixed in 1:3 aceto- alcohol and aceto-orcein preparations were made. Roots treated with HBR showed more mitotic activity, mitotic abnormalities and significant enlargements at the root tips when compared with control material. HBR application decreased total soluble protein content, superoxide dis- mutase (EC 1.15.1.1), catalase (EC 1.11.1.6) and peroxi- dase (EC 1.11.1.11) activities significantly at 1.0 lM HBR concentration. Data presented here is one of the first detailed analyses of HBR effect on barley root development. Keywords Hordeum vulgare L. Á Root development Á Mitotic abnormalities Á Superoxide dismutase Á Catalase Á Peroxidase Abbreviations BL Brassinolide BR Brassinosteroid BRs Brassinosteroids BSA Bovine serum albumin CAT Catalase EBR Epibrassinolide HBR Homobrassinolide PBS Phosphate buffered saline POX Peroxidase SOD Superoxide dismutase Introduction Brassinosteroids (BRs) are a class of plant steroid hor- mones whose general effect is the promotion of cell elon- gation, cell division, differentiation, disease resistance, stress tolerance and senecence throughout the plant life cycle (Clouse 2002; Nemhauser and Chory 2004; Mussig 2005). The functions of endogenous BRs have been ana- lyzed with BR-deficient mutants. All BR-deficient mutants showed an element of dwarfism, and some mutants showed altered leaf morphology, reduced male fertility, abnormal vascular formation, and de-etiolating of dark-grown seed- lings (Chono et al. 2003; Mussig et al. 2003; Kim et al. 2006). Exogenous BRs applications contributed to tre- mendous recent knowledge for understanding the physio- logical and molecular mechanisms related to BRs biology, distribution, interactions with other plant hormones, transport etc. (Symons et al. 2008). Amelioration of both biotic and abiotic stresses and genotoxicity could also be possible exogenous BRs applications (Hayat et al. 2007; Sondhi et al. 2008; Shahbaz et al. 2008). Brassinosteroids regulate the expression of numerous genes, affect the activity of complex metabolic pathways, and contribute to G. Kartal Á A. Temel Á E. Arican Á N. Gozukirmizi (&) Faculty of Science, Department of Molecular Biology and Genetics, Istanbul University, 34118 Vezneciler-Istanbul, Turkey e-mail: nermin@istanbul.edu.tr 123 Plant Growth Regul (2009) 58:261–267 DOI 10.1007/s10725-009-9374-z