ROOTING AND ACCLIMATIZATION OF IN-VITRO P ROPAGATED SHOOTS OF TILIA-CORDATA WEGA

In vitro propagated shoots of Tilia cordata 'Wega' could be rooted in vitro as well as ex vitro. In vitro almost 90 per cent of shoots forme d roots, ex vitro, however, up to 64 per cent of shoots rooted under p lastic film. Rooting was influenced by the shoot length and the durati on of the last subculture on the multiplication medium. Shoots should be longer than 5 mm and last subculture on multiplication medium shoul d be prolonged from 4 to 6 or 7 weeks. In vitro rooted shoots survived the transfer to the greenhouse up to 90 per cent provided they had a well developed root system and were 10 mm long at least. Survival of m icrocuttings was dependent on preconditioning of shoots as well as hum idity and substrate during acclimatization. A preconditioning of cultu res for 2 respectively 3 weeks in greenhouse improved the survival rat e considerably. Then about 80 per cent of microcuttings survived but o nly 70 per cent of them were rooted. In vitro rooted shoots started to grow 2 weeks after transfer to the greenhouse while ex vitro rooted m icrocuttings did not grow for 4 to 5 weeks after transfer. For Tilia c ordata 'Wega' in vitro rooting is recommended because rooting was very easy to regulate and at the same time plants were preconditioned for acclimatization.