ETHYLENE DOES NOT PROMOTE ADVENTITIOUS ROOT INITIATION ON APPLE MICROCUTTINGS

We investigated the role of ethylene on adventitious rooting of 'Gala' (easy-to-root) and 'Triple Red Delicious' (difficult-to-root) apple ( Malus domestica Borkh.) microcuttings. Root count increased significan tly as IBA level increased, with highest root counts on 'Gala'. Ethyle ne evolution increased significantly with IBA level without significan t differences between cultivars. Basal section removal of microcutting s in the area of root origin reduced root count without changing ethyl ene evolution. Ethylene treatment of proliferated shoots before microc utting excision failed to enhance rooting. IBA-induced ethylene evolut ion was eliminated nearly by AVG, but root count remained IBA dependen t. ACC reversed IBA plus AVG rooting inhibition, but ACC alone failed to influence root count. Polar auxin transport inhibitors NPA and TIBA stimulated ethylene evolution without increasing root count. Adventit ious rooting of apple microcuttings was not associated with ethylene. Chemical names used: 1-H-indole-3-butyric acid(IBA); aminoethoxyvinylg lycine(AVG); 1-aminocyclopropane-1-carboxylic acid (ACC); 2,3,5-triiod obenzoic acid (TIBA); ss-1-naphthylphthalamic acid (NAP).