Measurements of carbon isotope contents (13C/12C, δ 13C) in tree rings provide retrospective information about the short and long-term dynamics of plant ecophysiological, and paleo-environmental traits. They are commonly based on 13C/12C ratios of cellulose, and interpreted with respect to fractionation related to CO2 diffusion into plants and its fixation by Rubisco (diffusion-Rubisco - DR - fractionation). However, primary metabolites such as glucose are known to exhibit intramolecular 13C/12C differences of the order of 10h which reflect 13C fractionation by enzyme reactions downstream of Rubisco (Post-Rubisco - PR - fractionation). PR fractionation is not commonly considered in dendrochronological studies. It has not yet been investigated whether glucose monomers of cellulose show intramolecular 13C differences. Furthermore, it is unknown whether PR fractionation varies among years, and whether DR and PR fractionations introduce distinct 13C/12C signals. To test this, we isolated the glucose monomers of Pinus nigra tree rings, and determined 13C/12C ratios of all intramolecular glucose carbon positions by quantitative 13C NMR. The resulting dataset consists of 6 time series of positional 13C/12C ratios with annual resolution, extending from 1961 to 1995. Tree-ring glucose exhibits intramolecular 13C/12C differences of the order of 10h. Cluster analysis revealed several independent intramolecular 13C signals. These signals constitute distinct channels of information about both the DR interface and associated environmental triggers, as well as PR processes related to downstream C allocation. Thus, analysis of intramolecular 13C signals can extract more information with better quality from tree rings. This might enhance our understanding of biogeochemical, ecophysiological and paleo-environmental phenomena.