Quantitative and qualitative characteristics of cell wall components and prenyl lipids in the leaves of Tilia x euchlora trees growing under salt stress.

The study was focused on assessing the presence of arabinogalactan proteins (AGPs) and pectins within the cell walls as well as prenyl lipids, sodium and chlorine content in leaves of Tilia x euchlora trees. The leaves that were analyzed were collected from trees with and without signs of damage that were all growing in the same salt stress conditions. The reason for undertaking these investigations was the observations over many years that indicated that there are trees that present a healthy appearance and trees that have visible symptoms of decay in the same habitat. Leaf samples were collected from trees growing in the median strip between roadways that have been intensively salted during the winter season for many years. The sodium content was determined using atomic spectrophotometry, chloride using potentiometric titration and poly-isoprenoids using HPLC/UV. AGPs and pectins were determined using immunohistochemistry methods. The immunohistochemical analysis showed that rhamnogalacturonans I (RG-I) and homogalacturonans were differentially distributed in leaves from healthy trees in contrast to leaves from injured trees. In the case of AGPs, the most visible difference was the presence of the JIM16 epitope. Chemical analyses of sodium and chloride showed that in the leaves from injured trees, the level of these ions was higher than in the leaves from healthy trees. Based on chromatographic analysis, four poly-isoprenoid alcohols were identified in the leaves of T. x euchlora. The levels of these lipids were higher in the leaves from healthy trees. The results suggest that the differences that were detected in the apoplast and symplasm may be part of the defensive strategy of T. x euchlora trees to salt stress, which rely on changes in the chemical composition of the cell wall with respect to the pectic and AGP epitopes and an increased synthesis of prenyl lipids.

A near infrared spectroscopic study of the structural modifications of lime (Tilia cordata Mill.) wood during hydro-thermal treatment.

The modifications and/or degradation of lime (Tillia cordata) wood components during wood heat treatment under low temperature at about 140°C and 10% percentage of relative humidity were evaluated. The aim of this study was to obtain results by simple NIR coupled with second derivative, principal component analysis and two dimensional correlation spectroscopy in order to better understand how these techniques are able to evaluate structural differences resulted under hydro-thermal treatment of the wood over a period of 504h. The NIR spectra of treated samples were compared with the reference one. Due to the broad bands in the NIR spectra, the assignment and modifications occurring during treatment is difficult, therefore the second derivative principal component analysis were applied. Principal component analysis by first two components was able to differentiate the samples series, PC1 being considered as the time axis, and PC2 as the axis representing the structural modification of wood components. 2D NIR correlation spectroscopy was able to estimate the sequential order of the groups variations under the hydro-thermal treatment time as external perturbation, indicating as first moment changes the OH and CO groups from carbohydrates and lignin, followed by CarH, CH and CH2 groups from lignin, cellulose and hemicelluloses.