Microscopic mechanism of contraction of tension wood G-fiber due to boiling

Many woody eudicot plants form a secondary xylem composed of gelatinous fibers (G-fibers) called "tension wood" (TW) along the upper side tilted stem or branch. TW generates large tensile growth stress in longitudinal direction, allowing branch to develop negative-gravitropism response strong gravitational stimulus. This is because G-fiber tends contract direction as it matures. The matured also contracts upon boiling water (= hygrothermal treatment, i.e., HT-treatment), and moisture desorption drying treatment). These contractions occur cellulose-rich layer (G-layer) an innermost G-fiber. It still unsolved mystery how G-layer, which highly crystallized longitudinally oriented cellulose microfibrils (CMFs), during maturation, boiling, drying. In present study, specimen Konara oak (Quercus serrata L.) was subjected HT-treatment under different temperature time conditions, strain due treatment followed. Besides, mass loss Obtained results are summarized follows. (1) Green contracted when at higher than 40 °C, eventually converged constant value according each temperature. Magnitude HTR-strain positively correlated with range from 120 whereas normal wood (NW) specimen, does not explicitly less 100 °C. (2) Both NW specimens showed HT-treatment. rate increased rapidly by while only slight below There no significant difference between behavior From analyzing those results, physical CMF other non-cellulosic matrix components G-layer estimated. discussion further developed associate HT-contraction microscopic mechanisms two characteristic G-fiber, maturation shrinkage.