ORIGINAL PAPER Effects of hydrogen cyanamide on antioxidant enzymes’ activity, proline and polyamine contents during bud dormancy release in Superior Seedless grapevine buds Hatem Ben Mohamed • Ahmedou M. Vadel • Jan M. C. Geuns • Habib Khemira Received: 5 June 2011 / Revised: 20 August 2011 / Accepted: 24 August 2011 / Published online: 7 September 2011 Ó Franciszek Go ´rski Institute of Plant Physiology, Polish Academy of Sciences, Krako ´w 2011 Abstract The effect of hydrogen cyanamide (HC) on dormancy release, antioxidant enzyme’s activity and pro- line and free polyamine contents were investigated in ‘Superior Seedless’ grapevine buds. HC application caused a sharp decrease of catalase (CAT, EC 1.11.1.6) activity and a transient stimulation during the 5 days following treatment of peroxidase (POD, EC 1.11.1.7) and ascorbate peroxidase (APX, EC 1.11.1.11) activities. This coincided with an accumulation of total free polyamines, especially putrescine (Put). Proline content increased dramatically. There was a strong correlation between APX and POD activities and total free PAs and Put contents implying a possible stimulating effect of the latter compounds on these enzymes. These observations indicate that HC triggers an oxidative stress leading to bud endodormancy release. Afterward, as budbreak started, we observed a rapid proline and Put degradation; this could be responsible for reacti- vation of growth. Indeed, the decline in Put to (Spd ? Spm) ratio, reported here, may be considered as a reliable bio- chemical marker of bud growth resumption. Keywords Bud dormancy Á Grapevine Á Antioxidant enzymes Á Proline Á Polyamines Abbreviations AcCN Acetonitrile APX Ascorbate peroxidase BSA Bovine serum albumin CAT Catalase DMAB 3-Dimethylamino benzoic acid HC Hydrogene cyanamide MBTH 3-Methyl-2-benzothiazolinone hydrozone hydrochloride monohydrate PAs Polyamines POD Peroxidase Put Putrescine ROS Reactive oxygen species Spd Spermidine Spm Spermine Introduction Most temperate zone perennials undergo an annual period of bud dormancy which is a physiological state that reduces the ability of bud to burst in a reversible manner. End- odormancy, coinciding with winter, is an inhibition con- trolled from within the bud itself and released upon exposure to chilling. Hence, to resume growth, tree bud must receive an amount of chilling which is genetically controlled and varies among genotypes (Balandier et al. 1993; Egea et al. 2003). However, in mild-winter climates, most deciduous trees suffer from the lack of chilling which prolongs dormancy and triggers abnormal patterns of budbreak and development leading to low commercial production (Erez 1995). To alleviate this problem, artificial restbreaking agents are applied to regulate dormancy Communicated by M. Horbowicz. H. Ben Mohamed Á A. M. Vadel Á H. Khemira (&) Laboratory of Plant Biotechnology Applied to Crop Improvement, Department of Life Sciences, Faculty of Sciences of Gabe `s, University of Gabe `s, Cite ´ Erriadh, Zrig, 6072 Gabe `s, Tunisia e-mail: habibkhemira@yahoo.com J. M. C. Geuns Laboratory of Functional Biology, KU leuven, Kasteelpark Arenberg 31, 3001 Heverlee, Belgium 123 Acta Physiol Plant (2012) 34:429–437 DOI 10.1007/s11738-011-0839-0