Five specimens that contained a continuous gradient of wood, from normal to tension wood regions, were collected from an inclined yellow poplar (Liriodendron tulipifera), and the released strain of tensile growth stress was quantified. Ultraviolet (UV) microspectrophotometry was used to examine the relationship between lignin distribution in the cell wall and the intensity of tensile growth stress. The UV absorption of the secondary wall and the cell corner middle lamella decreased with increasing tensile released strain (i.e., tensile growth stress). The UV absorption in the compound middle lamella region remained virtually constant, irrespective of the tensile released strain. The absorption maximum (λmax) remained virtually constant in the secondary wall, the cell corner middle lamella, and the compound middle lamella region at 273–274, 277–278, and 275–278 nm respectively, irrespective of the tensile released strain. The ratios of the UV absorbance at 280 to 260 nm and 280 to 273 nm of the secondary wall decreased with increasing tensile released strain. The ratios in the cell corner and compound middle lamella region remained constant, irrespective of the tensile released strain. The lignin content of the secondary wall decreased, while the syringyl/guaiacyl ratio increased with increasing tensile released strain. Gelatinous fibers were not observed in the tension wood regions, but the secondary wall became gelatinous-layer-like, i.e., the lignin content and microfibrillar angle decreased and the cellulose content increased. A definite gelatinous layer seems to be important for generating greater tensile growth stress. It is concluded that a decrease in lignin and an increase in cellulose microfibrils parallel to the fiber axis in the secondary wall are necessary to produce large tensile growth stress.

Tensile growth stress and lignin distribution in the cell walls of yellow poplar, Liriodendron tulipifera Linn.

Growth stress (growth strain) in trees is usually evaluated using either a strain gauge or a dial gauge to measure the strain release. We summarize the techniques used to assess growth stress and compare the two methods. The dial gauge method measures change in distance between two pin targets when growth stress is released by sawing two grooves; from this the strain released is calculated. The absolute values of the strain released depended on whether the two grooves were sawn inside or outside the pin targets: the values in the first case were approximately twice those in the latter. If the grooves were sawn outside the pin targets, the values for the strain released were about the same as with the strain gauge method, in which the strain released by sawing a groove at each end of a strain gauge is measured. The released strain values were consistent when the strain gauge was glued to the outer surface of the secondary xylem after first fully removing the differentiating xylem. To release most of the surface growth stress and maximize released strain values, the optimal distance between the ends of the strain gauge and the grooves cut to release the growth stress was 3 to 5 mm. and the optimal depth of the groove was 5 to 10 mm. Most of the growth stress was released immediately when the grooves were sawn.

Techniques for measuring growth stress on the xylem surface using strain and dial gauges

Eucalyptus is an important genus in industrial plantations throughout the world and is grown for use as timber, pulp, paper and charcoal. Several breeding programmes have been launched worldwide to concomitantly improve growth performance and wood properties (WPs). In this study, an interspecific cross between Eucalyptus urophylla and E. grandis was used to identify major genomic regions (Quantitative Trait Loci, QTL) controlling the variability of WPs. Linkage maps were generated for both parent species. A total of 117 QTLs were detected for a series of wood and end-use related traits, including chemical, technological, physical, mechanical and anatomical properties. The QTLs were mainly clustered into five linkage groups. In terms of distribution of QTL effects, our result agrees with the typical L-shape reported in most QTL studies, i.e. most WP QTLs had limited effects and only a few (13) had major effects (phenotypic variance explained > 15%). The co-locations of QTLs for different WPs as well as QTLs and candidate genes are discussed in terms of phenotypic correlations between traits, and of the function of the candidate genes. The major wood property QTL harbours a gene encoding a Cinnamoyl CoA reductase (CCR), a structural enzyme of the monolignol-specific biosynthesis pathway. Given the number of traits analysed, this study provides a comprehensive understanding of the genetic architecture of wood properties in this Eucalyptus full-sib pedigree. At the dawn of Eucalyptus genome sequence, it will provide a framework to identify the nature of genes underlying these important quantitative traits.

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Comprehensive genetic dissection of wood properties in a widely-grown tropical tree: Eucalyptus

Summary This paper provides a brief, general background to growth stress, its undesired effects on sawlog utilization, and the methods that have been developed to counter these effects. The paper also describes three major methods used at present for growth strain measurement on tree or log surfaces, and discusses the need for an improved understanding of these methods.

/pdf/growth-stress-its-measurement-and-effects-4ijjnqq1r7.pdf

Growth stress, its measurement and effects

This review explores influences and impediments that impact a solid products industry's ability to profitably process a plantation hardwood resource. Profitably is taken to mean profitable over time, and therefore a sustainable industry. It reports on research covering:
· The solid wood products that can be made from plantation hardwoods
· The economic or commercial viability of producing these products from the available and potential resource
· The likely wood properties of this resource
· The relationship between silvicultural and genetic aspects of plantation hardwood forestry, and wood properties and product recovery.
While information on regrowth hardwood is included, this report focuses on growing and processing the eucalypt or closely related native hardwood species, such as Corymbia
spp., that make up most of Australia's hardwood plantations.

Eucalypt Plantations for Solid Wood Products in Australia - A Review‘If you don’t prune it, we can’t use it’

SYMMARY To assess the utility of the CIRAD-Fort% growth strain gauge for estimating stein growth stress, the relationship of longitudinal growth strain (LGS) with log-end splitting, sawn timber distortion and other tree and wood properties was studied in 23 ten-year-old Eucalyptus cloeziana trees. The CIRAD-Foret growth strain gauge appears to be useful as a means of predicting sawn timber distortion in young E. cloeziana trees. LGS correlated well with bow and spring and accounted for 50 and 30% of the respective total variation. The relationships of LGS with log end splitting, wood density, tree diameter and height were weak. However, distinct differences in wood density and sawtimber distortion were observed between trees with low and high strain. Trees with high growth strain were generally smaller with wood of significantly higher basic density and bow. Sampling position around the stem was not important and LGS increased with tree height.

A. Muneri

Papers

Relationships between surface growth strain and some tree, wood and sawn timber characteristics of Eucalyptus cloeziana