BIOLOGIA PLANTARUM 48 (1): 125-128, 2004 BRIEF COMMUNICATION Glutamine: a suitable nitrogen source for enhanced shoot multiplication in Cucumis sativus L. A.VASUDEVAN*, N. SELVARAJ**, A. GANAPATHI* 1 , S. KASTHURIRENGAN*, V. RAMESH ANBAZHAGAN* and M. MANICKAVASAGAM* Department of Biotechnology, Bharathidasan University, Tiruchirappalli-620024, Tamil Nadu, India* Department of Botany, Periyar E.V.R. College (Autonomous), Tiruchirappalli-620023, Tamil Nadu, India** Abstract Shoot tip explants of cucumber (Cucumis sativus L. cv. Poinsett 76) were cultured in vitro on Murashige-Skoog medium with L-glutamine, ammonium nitrate, adenine sulphate, asparagine, ammonium succinate, potassium nitrate and sodium nitrate as the nitrogen sources along with optimal concentration of 0.044 mM benzyladenine to study their effects on in vitro morphogenesis. The explants grown with 0.068 mM L-glutamine displayed the highest culture response (74.6 %) and greatest shoot number per explant (13.6) at the end of two subcultures. The explants cultured with other nitrogen sources resulted in low culture frequency and low number of shoots per explant accompanied by basal callusing and necrosis. Additional key words: benzyladenine, cucumber, shoot tip explants. ⎯⎯⎯⎯ The importance of the culture medium especially the contents of cytokinins and auxins in callus induction, organogenesis and multiplication has been demonstrated for a large number of plant species. However, the variation in hormone ratios cannot be the sole mechanism controlling in vitro developmental processes. Preece (1995) suggested that optimization of the mineral component of the culture medium would reduce the concentrations of plant growth regulators required. Influence of the absolute and relative amounts of nitrate and ammonium on the induction and differentiation of plant cell cultures have been reported for a number of in vitro systems (Halperin and Wetherell 1965, Wetherell and Dougall 1976, Chaleff 1983, Grimes and Hodges 1990, Cousson and Tran Thauh Van 1993). Reinert et al. (1967) observed that the concentration of nitrogen and the relative amounts of ammonium and nitrate in the culture medium would be critical for growth and morphogenesis of plant cells. The present study was undertaken to investigate the effects of various nitrogen sources in in vitro morphogenesis of cucumber cv. Poinsett 76 for the first time. Seeds of cucumber (Cucumis sativus L.) cv. Poinsett 76 (Indo-American hybrid seeds Pvt Ltd, Bangalore, India) were soaked in tap water for 15 min disinfected with 70 % alcohol for 1 min and 2.5 % (v/v) commercial bleach ‘Teepol’ (5.25 % sodium hypochlorite; Reckit & Benckiser of India Ltd, Kolkatta, India) for 15 min followed by three rinses with sterile distilled water. Seeds were further disinfected by soaking in 0.1 % mercuric chloride (m/v) for 3 min and rinsed four times with sterile distilled water. Disinfected seeds germinated in darkness for 48 h in 25 × 150 mm test tubes (Borosil, Mumbai, India) containing sterile moist cotton and then cultured at an irradiance of 30 μmol m -2 s -1 with 16-h photoperiod, and temperature of 25 ± 2 ºC. Shoot tips (5 mm length) from 5-d-old in vitro grown seedlings were excised and used as explants. The explants were inoculated in 25 × 150 mm test tubes containing 10 cm 3 of MS medium (Murashige and ⎯⎯⎯⎯ Received 28 January 2003, accepted 24 November 2003. Abbreviations: BA - 6-benzyladenine; MS medium - Murashige and Skoog medium. Acknowledgement: The corresponding author is thankful to Department of Science and Technology, Govt. of India, for financial support in the form of Indo-Israeli Collaborative project. 1 Corresponding author; fax: (+91) 431 2407045, e-mail: aganapathi2003@rediffmail.com 125