Surgical Experiments on Eucalypt Lignotubers

Abstract

Experiments involving surgery such as ring-barking or excision of lignotubers of seedling Eucalyptus st johnii plants are described. Removal of the strip of stem bark and cambium from between two lignotubers at the same node delays but does not prevent their lateral fusion. Ring-barking results in outgrowth of lignotuber buds below the ring and a check in growth, as compared with the untreated lignotuber at the same node. Excision of one lignotuber results in the formation of a 'replacement lignotuber' which lacks lignotuber buds; excision of both lignotubers at a node results in the formation of a pair of replacement lignotubers. Anatomical investigation shows that replacement lignotubers arise following conversion of stem cambial initials to lignotuber-type initials. The results lead to the following conclusions: outgrowth of lignotuber buds is suppressed by the seedling shoot; lignotuber buds do not form adventitiously. At a lignotuberous node, removal of stem or lignotuber cambium results in its replacement from the flanks of remaining lignotuber cambium. Stem cambium is not converted to lignotuber-type cambium by homeogenetic induction since it takes place also in the absence of lignotuber cambium.