Pii: S0168-9452(00)00212-0

An efficient protocol for in vitro propagation of Thamnocalamus spathiflorus (Trin.) Munro, an evergreen temperate bamboo, through multiple shoot formation from zygotic embryos excised from germinating seeds, as well as from nodal explants taken from a 2-year-old plant has been developed. Multiple shoot formation was standardized in both the cases on Murashige and Skoog (MS) medium supplemented with 5.0 mM 6-benzylaminopurine (BAP) and 1.0 mM indole-3-butyric acid (IBA). Clumps of three to four microshoots when transferred to plant growth regulator-free medium following 14 days’ initial culture on medium supplemented with 150.0 mM IBA, resulted in 100% rooting with five to 12 roots per rooted plant. Then, 18 months following the transfer of in vitro propagated plants into earthen pots containing soil and growth under outdoor conditions, gas and water vapour exchange rates were measured at different light levels (0, 100, 500, 1000, 1500, 2000 mmol s), and compared with seedlings of the same age. Light optima for photosynthesis were recorded 1000 mmol m s in in vitro propagated plants as well as seedlings. Water use efficiency increased with increase in the light intensity up to 1000 mmol m s and then decreased subsequently at higher light intensities. Stomatal conductance and transpiration also increased with the increase in light intensity up to 2000 mmol s. Intercellular CO2 concentration (Ci) and the ratio of intercellular CO2 concentration to ambient CO2 (Ci/Ca) decreased with the increase in light intensity up to 500 mmol s and then reached nearly constant levels at higher light intensities. The results show that in vitro propagated and hardened plants of T. spathiflorus are morphologically as well as functionally comparable to seed raised plants of the same age, within the limits of this study. © 2000 Elsevier Science Ireland Ltd. All rights reserved.