Carbon isotope discrimination (δ13C) as an indicator of vine water status and water use efficiency (WUE): Looking for the most representative sample and sampling time

Water status and must composition in grapevine cv. Chardonnay with different soils and topography and a mini meta‐analysis of the δ13C/water potentials correlation

“…Considering the recent literature the δ 13 C of grape sugars at harvest is, however, the best chemical integrator of water status during the ripening period and preferable to the use of leaves, with several authors reporting a lack of correlation between plant water status and/or WUE with leaf δ 13 C . Alternatively, the use of δ 18 O can be proposed, which has also been related to grapevine water deficit, but similar problems of variability in values appears between cultivars and regions …”

“…26 Integrals, as proposed in De Souza, 43 are probably a better option to correlate water potentials or other time-specific measurement of water status with 13 C. The use of a model to increase the time resolution of Ψ stem integrals at a daily time-step allowed a better approximation of the total water deficit during the ripening period, and greatly increased the accuracy of the relationships. 26 Considering the recent literature the 13 C of grape sugars at harvest is, however, the best chemical integrator of water status during the ripening period and preferable to the use of leaves, 23 with several authors reporting a lack of correlation between plant water status and/or WUE with leaf 13 C. 43 Alternatively, the use of 18 O can be proposed, which has also been related to grapevine water deficit, 44 but similar problems of variability in values appears between cultivars and regions. 36…”

“…Grapevine water status is generally assessed by leaf water potentials, while the use of carbon isotope composition to have a continuous integrator of the water status throughout the ripening period has been introduced more recently . The effectiveness and reliability of this method are therefore still a matter of discussion, with controversial results across studies . Basically, stable carbon isotope uptake is discriminated by ribulose 1,5‐diphosphate, which preferentially fixes 12 C, the most abundant carbon isotope.…”

“…[20][21][22] The effectiveness and reliability of this method are therefore still a matter of discussion, with controversial results across studies. 23,24 Basically, stable carbon isotope uptake is discriminated by ribulose 1,5-diphosphate, which preferentially fixes 12 C, the most abundant carbon isotope. When stomata are closed this kinetic preference is reduced, because the 13 C/ 12 C ratio increases in the substomatal chamber, and the primary photosynthetic products are enriched in 13 C. Water deficit is the main factor affecting this ratio.…”

The impact of plant water status on the gas exchange, berry composition and wine quality of Chasselas grapes in Switzerland

“…The latter has been correlated with a rise in the WUE i of non-irrigated vines compared to wellwatered vines. In addition, differences in leaf and fruit isotope signatures were observed (results not presented) under conditions of water stress (Bchir et al, 2016): the δ 13 C in leaves reflects not only the leaf ratio of Ci/Ca and the WUE of the current growing season but also the C assimilated in the previous year and its allocation during spring growth. There is generally an enrichment of 13 C in berries compared to leaves due to the import of carbon assimilates from the leaves after the onset of ripening, when water stress is high (stomata closed), thus supplying carbon assimilates enriched in 13 C. Lastly, a recent study (Spangenberg et al, 2017) showed that the analysis of carbon isotopes, undertaken in the solid residues and volatile organic components of wine, constitutes a very effective tool for estimating variations in the water status of plants and soils in different vineyards.…”