No abstract

The in vitro propagation of the new hybrid Hippeastrum · chmielii was analysed in this study. Propagation on solid medium, permanent immersion (flasks) and in a temporary immersion system (TIS) using quarters of in vitro grown bulblets as explants was compared. The TIS was constructed as twin-flasks system, the components of which were inexpensive. Within 4 weeks of culture on solid medium 3.9 new bulbs were formed per initial bulb and by using liquid culture systems this number was increased to 6.3-6.5. The number of daily immersions in TIS only slightly influenced the propagation rates and no significant differences to the permanently immersed treatments were observed. By adding flurprimidol (0.1-1.0 mg l )1 ) to the medium the propagation rate nearly doubled in liquid as well as in solid medium. Moreover, the size of the newly formed bulbs was increased by this inhibitor of gibberellic acid biosynthesis. Flurprimidol strongly reduced the elongation of the leaves while root formation was enhanced.

Correlation between ABA content in "mother" tissue and subsequent regeneration ability of Fritillaria imperialis cultured in vitro was investigated. In every experiment regeneration was always most efficient from plant material containing the lowest amount of free ABA: a leafy stem part, bulbs used for micropropagation in October and those stored two months at 30 °C prior to in vitro culture. However, no direct correlation between the absolute amounts of ABA and percentage of regeneration was found.

The experiments were performed to establish the conditions of <i>Platanus</i> × <i>acerifolia</i> Willd. and <i>Salix alba</i> L. cv. 'Tristis' reproduction by tissue culture. Two experiments were run. Leaf buds of <i>Platanus </i>and inflorescence buds of <i>Salix</i> were used. Growth of callus from <i>Platanus</i> and <i>Salix</i> in dependence on the concentration of growth substances (BA and NAA) and light and darkness conditions were compared. Rooted explants of <i>Salix alba</i> L. cv. 'Tristis' were obtained. The best results were obtained with <i>Platanus</i> × <i>acerifolia</i> in which rhizogenesis of amorphic callus occurred after two months of the experiment. Darkness was not a necessary condition for root formation. After three months of the experiment completely developed <i>Platanus</i> × <i>acerifolia</i> plants were obtained composed of a foliated shoots and a bundle of roots. They could be planted out on a sterile permanent substrate.

Explants of Platanus X acerifolia aseptically excised and placed on the MS medium supplemented with 0.1 mg/l vitamin C, 0.1 mg/1 BAP and 0.01 NAA will develop into complete plantlets. A month of darkness following seven weeks exposure to continuous light (1300-1500 lux) is necessary to induce rooting.