Syncarpia and Tristaniopsis (Myrtaceae) possess specialised fire-resistant epicormic structures

Abstract

On a worldwide basis epicormic resprouting after intense or crown fire is extremely rare, but is quite common in the eucalypts. Recent research has shown that the eucalypts have a highly modified epicormic structure that provides the bud-forming tissues with excellent protection from heat. A small number of non-eucalypts from the Myrtaceae have also been recorded as post-fire epicormic resprouters and it was considered of interest to determine whether this response was achieved through a similar or different structural adaptation. Leaf axils and epicormic structures of two species of Syncarpia and three species of Tristaniopsis were examined anatomically. Although the leaf axil anatomy of Syncarpia and Tristaniopsis was quite different (and different from that of the eucalypts), the epicormic structure was similar to that of the eucalypts, as the outer region of each epicormic strand possessed several strips of cells of meristematic appearance that were best developed in the innermost bark or even the outermost secondary xylem. As Syncarpia, Tristaniopsis and the eucalypts are only distantly related to each other within the Myrtaceae, it appears that this specialised fire-adapted epicormic structure may have developed multiple times within the family or originated from a common ancestor of the family.