REGULATION BY UNICONAZOLE-P AND GIBBERELLINS OF MORPHOLOGICAL AND ANATOMICAL RESPONSES OF FRAXINUS-MANDSHURICA SEEDLINGS TO GRAVITY

The present study deals with roles of gibberellins (GA(s)) in gravitro pic responses of woody stems of horizontally-positioned, 2-year-old se ed ling of Fraxinus mandshurica Rupr. var. japonica Maxim. The applica tion of uniconazole-P, an inhibitor of GA(s) biosynthesis, to stem nod es at various concentrations significantly inhibited not only righting the stems but also wood formation. The application of GA(s) (GA(3) an d GA(4)) in combination with uniconazole-P negated the inhibitory effe ct of the treatment of uniconazole-P alone. The GA(s) alone did not af fect wood formation, however, both GA(s) increased wood formation on b oth the upper and lower sides of horizontal stems with an increase in the concentration of combined uniconazole-P. In all of the seedlings, tension wood was formed on the upper side of stems. The application of uniconazole-P alone at various concentrations did not inhibit the for mation of tension wood fibres.