ORIGINAL PAPER Hydrogen peroxide involvement in formation and development of adventitious roots in cucumber Shiweng Li Æ Linggui Xue Æ Shijian Xu Æ Huyuan Feng Æ Lizhe An Received: 4 August 2006 / Accepted: 24 April 2007 / Published online: 31 May 2007 Ó Springer Science+Business Media B.V. 2007 Abstract Hydrogen peroxide (H 2 O 2 ), an active oxygen species, is widely generated in many biolog- ical systems. The present study demonstrates that H 2 O 2 was generated in seedling explants after the primary roots were removed, and it mediates the auxin response prior to adventitious root formation in cucumber (Cucumis sativus L. Ganfeng 8). When compared with the controls, treatment of cucumber seedling explants after primary roots removal with either 20–40 mM H 2 O 2 or 10 mM IAA significantly increased the number of adventitious roots, and treatment with 10–50 mM H 2 O 2 significantly in- creased the fresh weight of adventitious roots. The effects of H 2 O 2 on promoting the formation and growth of adventitious roots were eliminated by 2 mM ascorbic acid, 100 U CAT or 1 mM DPI, and the effects of IAA were eliminated by 4 mM ascorbic acid, 100 U CAT or 5 mM DPI. Treatment with either 4 mM ascorbic acid or 1–5 mM DPI inhibited the formation and growth of adventitious roots, and these inhibitory effects were partly reversed by exogenous H 2 O 2 .Furthermore, a higher concentration of endog- enous H 2 O 2 was detected in seedling explants 3 h after the primary roots were removed. However, in 10 mM DPI-treated seedling explants, the concentration of endogenous H 2 O 2 was markedly reduced by DPI. Results obtained suggest that H 2 O 2 may function as a signaling molecule, involved in the formation and development of adventitious roots in cucumber. Keywords Hydrogen peroxide Á Signaling Á Adventitious roots Á Cucumber Á Cucumis sativus L. Abbreviations ABA Abscisic acid CAT Catalase DPI Diphenylene iodonium cGMP Cyclic guanosine monophosphate IAA Indole-3-acetic acid MAPK Mitogen-activated protein kinase NADPH Nicotinamide adenine dinucleotide phosphate Introduction Hydrogen peroxide (H 2 O 2 ) is a form of reactive oxygen, having wide-ranging effects in many biolog- ical systems (Finkel and Holbrook 2000). Exposure S. Li Á S. Xu Á H. Feng Á L. An Key Laboratory of Arid and Grassland Ecology, Ministry of Education, School of Life Sciences, Lanzhou University, 222 Tianshui South Road, Lanzhou 730000, Gansu Province, P.R. China e-mail: lishweng@yahoo.com.cn S. Li Á L. Xue School of Chemical and Biological Engineering, Lanzhou Jiaotong University, Anning West Road, Lanzhou 730070, Gansu Province, P.R. China H. Feng (&) e-mail: Fenghy@lzu.edu.cn L. An (&) e-mail: lizhean@lzu.edu.cn 123 Plant Growth Regul (2007) 52:173–180 DOI 10.1007/s10725-007-9188-9