Abstract: The results of this investigation indicated that the crude stem extract of Eucalyptus LH₂₂ clone (Eucalyptus urophylla S. T. Blade Eucalyptus camaldulensis Dehnhardt), which was difficulty-to-root, inhibited evidendy the rooting rate and the length of roots of mung bean cuttings. Other-wise, there was no case in the U₆ clone (Eucalyptus urophylla S. T. Blade U₆ clone), which was easy-to-root. The crude extractions were purified by organic solvent extraction methods, and then all kinds of extractions were tested by seed germination. The experiments revealed that there were stron-ger inhibitory ingredients existed in water extract and ether extract by analysis of Duncan's SSR. But there was no inhibiting effect in the extract of U₆ clone. The inhibiting fractions were purified further by silica gel column chromatography and the result showed that different inhibitory activities were exis-ted among the several purified fractions. So, It's concluded that there were several different ingredi-ents of inhibitors in the stem of LH₂₂ clone and less inhibitors in the steni of U₆ clone.

Key words: E. urophylla×, E. camaldulensis LH₂₂ clone, E. urphylla U₆ clone, rooting inhibitors