Histochemistry of Reaction Wood Cell Walls in Two Species of Eucalyptus and in Tristania Conferta R.Br

Abstract

The results of extensive histochemical tests carried out on the walls of reaction wood cells in the stems of Eucalyptus spp. and Tristania conferta are presented. They are interpreted on the basis of the known chemistry and structure of such walls. These, in their turn, are related to the location of the cells in the stems. Of particular interest is the histochemical and structural heterogeneity of cell wall layer G. This heterogeneity is discussed in relation to the penetration of G by lignin precursors of extracellular origin and the possible release of phenolic substances from the protoplasts of living reaction wood, ray, and xylem parenchyma cells. The presence of peroxidase in the G layer is confirmed, and the marked tendency of G to stain when supplied with certain phenols and hydrogen peroxide demonstrated. Reduced lignification of G is tentatively attributed to retardation of lignin precursor penetration of G rather than to a lack of precursor availability.