Žiauka, J. and Kuusienė, S. 2006. Changes in Development of European Larch (Larix decidua Mill.) Vegetative Buds Induced by Plant Hormones. Baltic Forestry, 12 (2): 141-150

Effects of exogenously applied auxins and cytokinins on morphogenesis of European larch vegetative buds collected from 40-year-old tree were investigated using plant tissue culture techniques. Explants were prepared as short segments with axillary buds cut from the current year twigs or one-year-old twigs and were cultivated on modified MS medium. Different variants of nutrient medium were featured by different content of phytohormones: abscisic acid, auxins (indole-3-acetic acid and 2.4-dichlorophenoxyacetic acid), cytokinins (kinetin and 6-benzylaminopurine) and gibberellin (gibberellic acid-3). Abscisic acid negatively affected organogenesis in larch vegetative buds. Negative effect of auxins on the development of basal needles was significant after larch buds were cultivated in vitro 25 days but after 75 days the tendency was observed that the number of explants with newly developing shoots increases with increasing concentration of auxins. Auxins strongly increased callus formation on larch explants. Cytokinins blocked elongation of needles and induced formation of long-shoot primordia (structures able to form new meristems and to develop adventitious buds). Positive effect of cytokinins on viability of larch buds was significant in dark-grown explants, while large amounts of cytokinins have decreased the viability of light-grown explants (but less significantly). Gibberellin was able to promote the development of axial needles in the shoot apex zone.

Key words:larch, bud development, cytokinins, auxins, gibberellin, phase change