A General Theory for the Origin of Growth Stresses in Reaction Wood: How Trees Stay Upright

Abstract

A general theory for the origin of growth stresses in the reaction wood of trees is presented. In both gymnosperms and arboreal dicotyledons, stress is considered to arise from the cellulosic component of the wood. It is suggested that in gymnosperms, cellulose microfibrils behave as helical springs. The helical springs are thought to be laid down in a compressed state and thus exert a compressive force which acts to right or stabilise the tree.In arboreal dicotyledons the cellulose microfibrils are laid down as extended, longitudinally oriented springs and thus exert a tensile force tending to right or stabilise the tree.Contrary to the prevailing view, lignin is not considered to be involved in the generation of growth stress in reaction wood. It is suggested that the sole function of lignin is to cement the cellulosic constituents into a whole, thus ensuring the transmission of stresses through the wood. The low values of lignin often reported from tension wood and especially from gelatinous fibres is seen as a mechanism to facilitate the contraction of microfibils thus maximising longitudinal tensile stress. The high values of lignin in of compression wood is seen as a mechanism to increase the compressive strength of compression wood.

Maturation Stress Generation in Poplar Tension Wood Studied by Synchrotron Radiation Microdiffraction

“…However, several recent publications have greatly improved our knowledge about the ultrastructure, chemical composition, molecular activity, mechanical state, and behavior of tension wood. Different models have been proposed and discussed to explain the origin of maturation stress (Boyd, 1972;Bamber, 1987Bamber, , 2001; Okuyama et al, 1 These authors contributed equally to the article. * Corresponding author; e-mail clair@lmgc.univ-montp2.fr.…”

Determination of Differences in Anatomical and Chemical Characteristics of Tension and Opposite Wood of 8-Year Old Eucalyptus Globulus

“…The main factors responsible for the formation of this type of wood are: soil subsidence, heavy loads, winds and any other gravitational stimulus that affect the natural trend of a tree's vertical growth (Bamber 2001). The cellulose microfibrils in tension wood act like stretched longitudinal springs that pull the leaning stem upright to its normal position (Bamber 2001;Clair et al 2006).…”

“…The main factors responsible for the formation of this type of wood are: soil subsidence, heavy loads, winds and any other gravitational stimulus that affect the natural trend of a tree's vertical growth (Bamber 2001). The cellulose microfibrils in tension wood act like stretched longitudinal springs that pull the leaning stem upright to its normal position (Bamber 2001;Clair et al 2006). Even though tension wood is most often associated with leaning or bent trees it has also been reported in well grown, straight, vertical stems of several species including Eucalyptus (Wahyudi et al 1999(Wahyudi et al , 2000Washusen and Ilic 2001;Washusen 2002).…”

Poplar genes encoding fasciclin‐like arabinogalactan proteins are highly expressed in tension wood

“…Tension wood is also characterized by a higher proportion of fibres, a lower proportion of vessels and a higher longitudinal shrinkage than normal wood ( Jourez et al ., 2001). Different models have been proposed in order to link these biochemical and anatomical characteristics to the mechanical properties of tension wood (Bamber, 2001). Okuyama et al .…”