Micropropagation of Dev-ringal [Thamnocalamus spathiflorus (Trin.) Munro] - a temperate bamboo, and comparison between in vitro propagated plants andseedlings

An efficient protocol for in vitro propagation of Thamnocalamus spathifloru s (Trin.) Munro, an evergreen temperate bamboo, through multiple shoot form ation from zygotic embryos excised from germinating seeds, as well as from nodal explants taken from a 2-year-old plant has been developed. Multiple s hoot formation was standardized in both the cases on Murashige and Skoog (M S) medium supplemented with 5.0 mu M 6-benzylaminopurine (BAP) and 1.0 mu M indole-3-butyric acid (IBA). Clumps of three to four microshoots when tran sferred to plant growth regulator-free medium following 14 days' initial cu lture on medium supplemented with 150.0 mu M IBA, resulted in 100% rooting with five to 12 roots per rooted plant. Then, 18 months following the trans fer of in vitro propagated plants into earthen pots containing soil and gro wth under outdoor conditions, gas and water vapour exchange rates were meas ured at different light levels (0, 100, 500, 1000, 1500, 2000 mu mol(-2) s( -1)), and compared with seedlings of the same age. Light optima for photosy nthesis were recorded similar to 1000 mu mol m(-2) s(-1) in in vitro propag ated plants as well as seedlings. Water use efficiency increased with incre ase in the light intensity up to 1000 mu mol m(-2) s(-1) and then decreased subsequently at higher light intensities. Stomatal conductance and transpi ration also increased with the increase in light intensity up to 2000 mu mo l(-2) s(-1). Intercellular CO2 concentration (C-i) and the ratio of interce llular CO2 concentration to ambient CO2 (C-i/C-a) decreased with the increa se in light intensity up to 500 mu mol(-2) s(-1) and then reached nearly co nstant levels at higher light intensities. The results show that in vitro p ropagated and hardened plants of T. spathiflorus are morphologically as wel l as functionally comparable to seed raised plants of the same age, within the limits of this study. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.