INFLUENCE OF EXPLANT SOURCE, PLANT-GROWTH REGULATORS AND CULTURE ENVIRONMENT ON CULTURE INITIATION AND ESTABLISHMENT OF QUERCUS-ROBUR L IN-VITRO

Suitable cytokinin supplements and culture environments have been dete rmined for the initiation and establishment of shoot cultures of Querc us robur seedling tissue. Initiation of axillary shoot development fro m nodal explants required culture medium supplemented with BA (6-benzy lamminopurine). The greatest numbers of stem segments for culture prol iferation were obtained using 1.0 mg l(-1) BA after 56 d culture, The frequency of shoot development and subsequent formation of multiple sh oots at initiation was influenced by the position of the nodal explant in the seedling shoot, incubation temperature and daylength, Explants from basal and apical regions, which contained multiple axillary buds , produced the lowest frequencies of axillary shoot development and mu ltiple shoot formation, many remained quiescent, Axillary shoot develo pment was greatest in single nodal explants excised from the mid-stem positions, elongated regions of the shoot where nodes were formerly as sociated with a leaf, Higher temperatures stimulated shoot formation w ith greater numbers of stem segments for culture multiplication being obtained from nodal explants incubated at 25 degrees C, Axillary shoot development was promoted in nodal explants maintained under daylength s of 16 h or more, Stem segments cut from axillary shoots which develo ped from nodal explants were used to establish shoot multiplication cu ltures on medium supplemented with 0.4 mg l(-1) BA, Shoot formation fr om stem segments was greater at higher incubation temperatures of 25 d egrees C and 30 degrees C. Multiplication coefficients for stem segmen ts increased after one subculture.