-1 Effects of growth regulators on inflorescence proliferation of Bambusa edulis Choun-Sea Lin 1, *, John Vidmar 2 and Wei-Chin Chang 3 1 Department of Biotechnology, China Institute of Technology, Taipei, Taiwan 115, Republic of China; 2 Alberta Research Council, Edmonton, Alberta, Canada; 3 Institute of Botany, Academia Sinica, Taipei, Taiwan 115, Republic of China; *Author for correspondence (e-mail: cslin99@hotmail.com; phone: +886-2-27899590 ext 120) Received 2 December 2003; accepted in revised form 13 March 2004 Key words: Cytokinins, NAA, Thidiazuron Abstract The effects of various growth regulators in Bambusa edulis inflorescence proliferation were studied. Cytokinin is essential for inflorescence proliferation. Thidiazuron (TDZ) had been the most efficient cytokinin to induce inflorescence proliferation. The optimal TDZ concentration was 0.01–0.1 mg l À1 . In- florescences did not proliferate in media containing auxin, gibberellic acid (GA 3 ), abscisic acid (ABA), or 1-amino- cyclopropane-1-carboxylic acid (ACC) alone. In TDZ-containing medium, the proliferation ratio decreased when the naphthaleneacetic acid (NAA) concentration higher than 5 mg l À1 . Abbreviations: ACC – 1-amino- cyclopropane-1-carboxylic acid; ABA – abscisic acid; BA – n-benzylade- nine; GA 3 – gibberellic acid; MS – Murashige and Skoog basal medium; NAA – naphthaleneacetic acid; PBA – n-benzyl-9-(2-tetrahydropyranyl)-adenine; TDZ – thidiazuron Introduction It is generally believed that plants must reach a minimum stage of development before they will flower. (Hopkins 1999). Although bamboo flow- ering could be induced in vitro on a medium con- tained cytokinin (Nadgauda et al. 1990; Chambers et al. 1991; Rout and Das 1994; Lin and Chang 1998; Lin et al. 2003a), the in vitro propagation of vegetative shoots is still required to induce flow- ering. How to maintain the adult phase and to produce new inflorescences is a challenge. The flowering plantlets of bamboo may have a prac- tical value in wide hybridization and in vitro fer- tilization studies, because in vitro flowering of regenerated plantlets can be induced at any time of the year. We demonstrated that a continuous reproductive tissue of Bambusa edulis could be generated in vitro without vegetative organ (Lin et al. 2003b). Plant growth regulators have various effects on plant development. Concentration and ratio of plant growth regulators influence plant develop- ment. For example, cytokinin acts synergistically with auxin to promote cell division in vitro, and acts antagonistically to auxin in shoot initiation in callus cultures (Taiz and Zeiger 1991). Conse- quently, systematically examining the effects of medium compounds on in vitro inflorescence pro- liferation is important. Here, we report different plant growth regulators on inflorescence prolifer- ation in vitro. Plant Growth Regulation 43: 221–225, 2004. Ó 2004 Kluwer Academic Publishers. Printed in the Netherlands. 221