title: New research perspectives from a novel approach to quantify tracheid wall thickness.
abstract: The analysis of xylem cell anatomical features in dated tree rings provides insights into xylem functional responses and past growth conditions at intra-annual resolution. So far, special focus has been given to the lumen of the water-conducting cells, whereas the equally relevant cell wall thickness (CWT) has been less investigated due to methodological limitations. Here we present a novel approach to measure tracheid CWT in high-resolution images of wood cross-sections that is implemented within the specialized image-analysis tool 'ROXAS'. Compared with the traditional manual line measurements along a selection of few radial files, this novel image-analysis tool can: (i) measure CWT of all tracheids in a tree-ring cross-section, thus increasing the number of individual tracheid measurements by a factor of ~10-20; (ii) measure the tangential and radial walls separately; and (iii) laterally integrate the measurements in a customizable way from only the thinnest central part of the cell walls up to the thickest part of the tracheids at the corners. Cell wall thickness measurements performed with our novel approach and the traditional manual approach showed comparable accuracy for several image resolutions, with an optimal accuracy-efficiency balance at 100× magnification. The configurable settings intended to underscore different cell wall properties indeed changed the absolute levels and intra- and inter-annual patterns of CWT. This versatility, together with the high data production capacity, allows to tailor the measurements of CWT to the specific goal of each study, which opens new research perspectives, e.g., for investigating structure-function relationships, tree stress responses and carbon allocation patterns, and for reconstructing climate based on intra- and inter-annual variability of anatomical wood density.
authors.affiliation: Department TeSAF - Department of Territorio e Sistemi Agro-Forestali, Università degli Studi di Padova, Viale dell'Università 16, 35020 Legnaro (PD), Italy.
authors.forename: Angela Luisa
authors.initials: AL
authors.lastname: Prendin
authors.affiliation: Department TeSAF - Department of Territorio e Sistemi Agro-Forestali, Università degli Studi di Padova, Viale dell'Università 16, 35020 Legnaro (PD), Italy.
authors.forename: Giai
authors.initials: G
authors.lastname: Petit
authors.affiliation: Department TeSAF - Department of Territorio e Sistemi Agro-Forestali, Università degli Studi di Padova, Viale dell'Università 16, 35020 Legnaro (PD), Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Carrer
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Fonti
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland.
authors.forename: Jesper
authors.initials: J
authors.lastname: Björklund
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland.|Climatic Change and Climate Impacts, Institute for Environmental Sciences, 66 Bvd Carl Vogt, 1205 Geneva, Switzerland.
authors.forename: Georg
authors.initials: G
authors.lastname: von Arx
mesh_terms: D002473:Cell Wall / Q000648:ultrastructure*; D014197:Trees / Q000033:anatomy & histology; D014934:Wood / Q000033:anatomy & histology*; D052584:Xylem / Q000033:anatomy & histology*
keywords: ROXAS; automated image analysis; carbon allocation; quantitative wood anatomy; radial cell wall thickness; tangential cell wall thickness