Within-Tree Variation in Anatomical Properties of Compression Wood in Radiata Pine

Abstract

Two trees of radiata pine, one showing severe lean, the other growing almost vertically, were assessed for the presence and anatomical properties of compression wood, including anatomy, lignin distribution, microfibril angle, basic density, radial and tangential lumen diameter and cell wall thickness. Both trees contained significant amounts of compression wood although the severity and amount of compression wood was greater in the leaning tree. Changes in lignin distribution seem to be characteristic of the mildest forms of compression wood with reduced lignification of the middle lamella representing the earliest change observed from normal wood. An increase in microfibril angle was associated with both mild and severe compression wood although examples of severe compression wood with the same or smaller microfibril angles than opposite wood, or with very small microfibril angles, were found. When segregated into mild and severe compression wood the average difference in microfibril angle was 4° and 8° respectively compared with opposite wood. Within-ring distribution of microfibril angle was different in severe compression wood compared to opposite wood with higher angles in the latewood.Severe compression wood showed a 22% increase in basic density compared to mild compression wood and opposite wood. The increased density was accounted for in terms of a 26% increase in tracheid wall thickness throughout the growth ring, offset by a 9% increase in radial lumen diameter, slightly greater in the latewood. There were no significant changes in density or cell dimensions in mild compression wood compared with opposite wood.

Fluorescence-Detected Linear Dichroism of Wood Cell Walls in Juvenile Serbian Spruce: Estimation of Compression Wood Severity

“…But, in conifer juvenile wood, fibrils in all cell wall layers are oriented transversally i.e. at high angles to tracheid axis, with angles increased in CW (Plomion et al, 2001, Donaldson 2004, 2008. On the cross sections of juvenile P. omorika stems, a grey colour unambiguously represents cellulose fibrils oriented at about 45 to the reference line (tracheid X-axis).…”

“…The NW tracheids are rectangular 8 in shape, with thin cell walls. Such differences in shape and thickness of cell walls of NW and CW in conifers were previously defined and reviewed (Donaldson 2004, Plomion et al 2001). …”

“…CW occurs in a range of gradations from mild to severe. Juvenile trees growing in an open or wind-exposed environment produce large amounts of randomly distributed mild CW (Donaldson et al 2004), so NW is often uncommon in juvenile trees.…”

“…Severe CW is characterized by increased wall thickness, reduced lumen diameter, reduced tracheid length, rounder cell cross-sectional profile, the absence of S3 layer, and the presence of intercellular spaces (Yumoto et al 1983, Donaldson 2004, Plomion et al, 2001. CW contains higher amounts of lignin and lower amounts of cellulose (Nanayakkara et al 2009).…”

“…Despite its limited natural range, P. omorika is considered to be one of the most adaptable spruces. It belongs to slow growing conifer species, in which compression wood typically occurs in a severe form (Donaldson et al, 2004;Timell 1986). These two features make Serbian spruce a challenging model plant for studying cell wall structure and organization.…”