EFFECT OF PH AND 1H-INDOLE-3-BUTYRIC ACID (IBA) ON ROOTING OF APPLE MICROCUTTINGS

Involvement of pH and IBA on adventitious root initiation was investig ated with Malus domestica Borkh. microcuttings. The pH of unbuffered r oot initiation medium (RIM) increased from 5.6 to 7 within 2 days. Buf fering with 2[N-morpholino] ethanesulfonic acid (MES) adjusted to spec ific pHs with potassium hydroxide prevented pH changes and resulted in a 2-fold higher root count at pH 5.5 compared to pH 7 or unbuffered m edium. As pH decreased, lower concentrations of IBA were required to i ncrease root counts. Colorimetric measurement of IBA in buffered RIM s howed greater IBA loss and higher root count were associated with lowe r pH levels in all cultivars. This suggests that IBA loss from RIM dep ends on medium pH, which affects root count. Root count differences be tween easy-to-root through difficult-to-root cultivars were not consis tent with amount of IBA loss from RIM. Cultivar differences in root co unt could not be explained solely by IBA loss from RIM.