Isotopic comparison and correlation of δ13C between bulk wood and cellulose of Vitis vinifera L.

This study aims to compare the δ13C isotopic signal between bulk wood and α-cellulose in wood samples from the main trunk of Vitis vinifera L. to verify whether α-cellulose extraction is necessary for ecophysiological studies in this species. A pool of samples from different cultivars and provenances was analysed. The wood samples were obtained from cross sections of the main trunk of the plants, from where the annual growth rings were anatomically recognised, dated to the year of formation, and then separated. Each ring comprised both early- and latewood portions. For each sample, a part was saved as bulk wood and another part was destined for α-cellulose extraction. The δ13C isotopic signal in both types of samples was performed on a Vario Micro Cube elemental analyser coupled to a continuous flow mode to an isotope ratio mass spectrometer. A least squares regression was used to verify the correlation between the two variables. The results showed that the correlation coefficient of the isotopic signal for both types of samples was 0.86, and the slope of the regression line was not significantly different from one. Those results indicated that it is acceptable to use bulk wood instead of α-cellulose for δ13C isotopic studies in Vitis vinifera. This study is the first to compare isotopic δ13C signals between bulk wood and α-cellulose in grapevines. Therefore, this study constitutes a starting point to explore dendrochemical techniques based on the analysis of the δ13C content in Vitis vinifera wood, with the aim of deepening the ecophysiological knowledge of the grapevine in relation to water economy strategies and the links with climate variability and change.