Eucalyptus regnans (Myrtaceae): A fire‐sensitive eucalypt with a resprouter epicormic structure

Abstract

Determining the location of buds and bud-forming meristems and hence the level of protection from heat is essential to understanding plant response to fire. Most eucalypts resprout readily from the stem (epicormic resprouting) and the base after felling or high intensity fire. In contrast, Eucalyptus regnans is one of the few eastern Australian fire-sensitive, obligate seeder eucalypts. Some authors have suggested that the relatively weak epicormic resprouting is due to a lack of bud-forming structures. Epicormic strands from the bark and outer xylem of three very large trees and two saplings were examined anatomically. Epicormic bud-forming structures were found in all samples examined. The bud-forming capacity consisted of narrow, radially elongated strips of cells of meristematic appearance. These strips were continuous from the outermost secondary xylem through to the outer bark. Bark was relatively thick at the base of the large trees, but remarkably thin above this basal skirt. Eucalyptus regnans was found to possess the apparently fire-adapted epicormic strands previously described in other eucalypts, thus showing its fire-adapted lineage. However, this fire-sensitive species apparently directs much of its resources to rapid height-growth rates in younger trees, rather than to vegetative fire survival.

Flammable biomes dominated by eucalypts originated at the Cretaceous–Palaeogene boundary

“…In eucalypts, the distinctive epicormic resprouting anatomy has been strictly conserved until the present, despite changes in habitat and response to fire. For example, Eucalyptus brachyandra grows on fire-protected cliffs and E. regnans dominates wet sclerophyll forest and, although usually killed by high-intensity fires, still retains capacity to resprout epicormically after less intense fires 10 .…”

“…In the fifth type (E), epicormic bud-forming structures are apparently absent. Various processes have been implicated in the death of epicormic buds or failure in their initial development 10 .…”

“…We scored a matrix for five epicormic structural types across 66 myrtaceous taxa studied to date [8][9][10][11]50 and for their biome of occurrence (Supplementary Table S1). In the first (type A), the bud-forming cells comprise meristem strips (that is, radially oriented strips of cells of meristematic appearance) and are present at all depths in the bark, and in most cases probably extend a short distance into the outer secondary xylem.…”

Propagação de Eucalyptus cloeziana F. Muell

“…Eucalyptus estão próximos ao câmbio vascular que podem estar presentes desde a superfície do fuste da árvore até áreas mais profundas, próximas ao xilema secundário (BURROWS, 2002;BURROWS et al, 2008;WATERS et al, 2010). A estrutura dos centros meristemáticos é amplamente conservada nas espécies de Eucalyptus e outros gêneros correlacionados (BURROWS, 2002;BURROWS, 2008;CRISP et al, 2011).…”

“…Barra = 1,0 cm; I = Brotações epicórmicas induzidas em megaestacas de casca de maior espessura. Barra = 0,5 cm As brotações epicórmicas em Eucalyptus surgem a partir de células meristemáticas na casca das árvores, próximos ao câmbio vascular (BURROWS, 2000(BURROWS, , 2002WATERS et al, 2010). A indução das brotações epicórmicas nas megaestacas ocorreu pela quebra do balanço hormonal presente nas matrizes que inibia a sua formação.…”