Influence of explant source, plant growth regulators and culture environment on culture initiation and establishment of Quercus robur L. in vitro

Abstract

Suitable cytokinin supplements and culture environments have been determined for the initiation and establishment of shoot cultures of Quercus robur seedling tissue. Initiation of axillary shoot development from nodal explants required culture medium supplemented with BA (6-benzylamminopurine). The greatest numbers of stem segments for culture proliferation were obtained using 1.0 mg l-1 BA after 56 d culture. The frequency of shoot development and subsequent formation of multiple shoots 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 multiple shoot formation, many remained quiescent. Axillary shoot development was greatest in single nodal explants excised from the midstem positions, elongated regions of the shoot where nodes were formerly associated with a leaf. Higher temperatures stimulated shoot formation with greater numbers of stem segments for culture multiplication being obtained from nodal explants incubated at 25 °C. Axillary shoot development was promoted in nodal explants maintained under daylengths of 16 h or more. Stem segments cut from axillary shoots which developed from nodal explants were used to establish shoot multiplication cultures on medium supplemented with 0.4 mg l-1 BA. Shoot formation from stem segments was greater at higher incubation temperatures of 25 °C and 30 °C. Multiplication coefficients for stem segments increased after one subculture.