Carbon and nitrogen stable isotope variations in leaves of two grapevine cultivars (Chasselas and Pinot noir): Implications for ecophysiological studies

We investigated the within- and between-leaf variability in carbon nitrogen isotope composition (?13C ?15N) total (TN) content two grapevine cultivars (Vitis vinifera cv. Chasselas Pinot noir) field-grown under rain-fed conditions. The within-leaf was studied discs sampled from base-to-tip left right regions margin to midrib. intra- interplant by comparing leaves at different positions along shoot (basal, median, apical). In both cultivars, a decrease ?13C base tip observed, which is line with an upward gradient of stomatal density chlorophyll concentration. Less important, but still significant differences were observed between discs. leaf TN ?15N values differed showed smaller variations than values, no systematic spatial trends. intraleaf ?13C, ?15N, suggest that behavior, CO2 fixation, concentrations, chemical components heterogeneous leaves. At canopy scale, apical had less 13C more 15N basal leaves, indicating their photosynthetic capacity remobilizations old, senescing younger Overall, this study demonstrates patchiness species-specificity assimilation fractionation. These findings care must be taken not overinterpret foliar studies based on fragmented material as markers physiological biochemical responses environmental factors.