GROWTH OF ROOTED GALA APPLE MICROCUTTINGS EX-VITRO AS INFLUENCED BY INITIAL ADVENTITIOUS ROOT COUNT

The role of the number of adventitious roots of Malus domestica Borkh. 'Gala' microcuttings in vitro on ex vitro root and shoot growth was i nvestigated. Root initiation treatments consisted of IBA at 0, 0.15, 1 .5, 15, and 150 muM in factorial combination with media at pH 5.5, 6.3 , and 7.0. IBA concentrations significantly influenced final root coun t and shoot fresh and dry weights, but not plant height, leaf count, o r root fresh and dry weights at 116 days. Between 0 and 0.15 muM IBA, final root counts were similar, but at 1.5, 15, and 150 muM IBA, root counts increased by 45%, 141%, and 159%, respectively, over the contro l. The pH levels did not affect observed characteristics significantly . There was no significant interaction between main effects. A signifi cant positive linear relationship was found between initial and final root count. The results suggest a limited association between high ini tial adventitious root count and subsequent growth. Chemical name used : IH-indole-3-butyric acid (IBA).