Journal Article

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

Jullien, Delphine, Clair, Bruno, Pilate, Gilles, Sugiyama, Junji, Riekel, Christian, Alméras, Tancrède

2011

Overview

Tension wood is widespread in the organs of woody plants. During its formation, it generates a large tensile mechanical stress called maturation stress. Maturation stress performs essential biomechanical functions such as optimizing the mechanical resistance of the stem, performing adaptive movements, and ensuring the long-term stability of growing plants. Although various hypotheses have recently been proposed, the mechanism generating maturation stress is not yet fully understood. In order to discriminate between these hypotheses, we investigated structural changes in cellulose microfibrils along sequences of xylem cell differentiation in tension and normal wood of poplar (Populus deltoides x Populus trichocarpa 'I45-51'). Synchrotron radiation microdiffraction was used to measure the evolution of the angle and lattice spacing of crystalline cellulose associated with the deposition of successive cell wall layers. Profiles of normal and tension wood were very similar in early development stages corresponding to the formation of the S1 layer and the outer part of the S2 layer. Subsequent layers were found with a lower microfibril angle (MFA), corresponding to the inner part of the S2 layer of normal wood (MFA approximately 10°) and the G layer of tension wood (MFA approximately 0°). In tension wood only, this steep decrease in MFA occurred together with an increase in cellulose lattice spacing. The relative increase in lattice spacing was found close to the usual value of maturation strains. Analysis showed that this increase in lattice spacing is at least partly due to mechanical stress induced in cellulose microfibrils soon after their deposition, suggesting that the G layer directly generates and supports the tensile maturation stress in poplar tension wood.

• Publisher: American Society of Plant Biologists,Oxford University Press ; American Society of Plant Biologists
• Subject: anatomy & histology / Biological and medical sciences / Biomechanical Phenomena / CELL BIOLOGY AND SIGNAL TRANSDUCTION / Cell differentiation / Cell walls / Cellulose / Cellulose - metabolism / chemistry / Crystal lattices / Crystallization / Crystals / Developmental biology / developmental stages / early development / evolution / Fundamental and applied biological sciences. Psychology / Genetics / growth & development / Life Sciences / mechanical stress / metabolism / Microfibrils / Microfibrils - chemistry / physiology / plant organs / Plant physiology and development / Plants / Plants genetics / Populus / Populus - anatomy & histology / Populus - growth & development / Populus - physiology / Populus generosa / spatial distribution / stems / Stress, Mechanical / Synchrotrons / Tensile stress / Tension / Tension wood / Wave diffraction / Wood / Wood - anatomy & histology / Wood - growth & development / Wood - physiology / Wood structure / Woody plants / X-Ray Diffraction