Regeneration of damaged roots of ‘young’ and ‘old’ Eucalyptus sieberi with reference to susceptibility to infection by Phytophthora cinnamomi root rot.  I. W. Smith and G. C. Marks.  December 1982.  9 pp. (unpubl.)

SUMMARY

Root regeneration of young and old trees of Eucalyptus sieberi L. Johnson (silvertop) was examined over a four-month period in the field by replacing the soil around the severed ends of large suberised roots with damp vermiculite enclosed in polystyrene boxes. The vermiculite was readily removable to allow observation of the roots.

Masses of parenchymatous callus appeared at the cut ends of some roots and gave rise in some cases to many large fleshy roots. In other cases, large, fast-growing white roots developed from various positions along the severed root contained in the polystyrene box. These roots rapidly reproduced a new root system by repeated branching.

The number of roots and total root length recorded for the younger trees was significantly greater than that recorded for either ‘mature’ or ‘over-mature’ trees. The reduced ability of older trees to replace damaged roots may be a factor contributing to their greater sensitivity to disease produced by Phytophthora cinnamomi Rands (phytophthora root rot).