Rooting of stem cuttings of Eucalyptus: A rooting inhibitor in adult tissue

The available physiological evidence suggests that ontogenetic ageing of E. Grandis seedlings involves a direct and quantitative association between decreased rooting ability of stem cuttings and increased levels of a rooting inhibitor in the tissue forming the base of the cutting. As detected by bioassay, this inhibitor is present only in adult tissue, which very rarely forms roots from stem cuttings. It is absent in easily rooted seedling stems of all Eucalyptus species tested, but it is also absent in the easily rooted adult tissue of the exceptional species E. deglupta. The ability of seedling cuttings of E. deglupta to root very easily in water provides an appropriate bioassay for monitoring the presence of inhibitor in other Eucalyptus species.