The assessment of vine water and nitrogen uptake by means of physiological indicators influence on vine development and berry potential (Vitis vinifera L. cv Merlot, 2000, Bordeaux)

Vine water and nitrogen uptake can be assessed by means of physiological indicators in field conditions. In this study, pre-dawn leaf water potential (ψB) and stem water potential (ψT) were used to indicate vine water status of Vitis vinifera L cv. Merlot. Carbon isotope composition of grape sugar (ΔC13) was used as an integrative indicator of vine water deficit during the ripening period. Must assimilable nitrogen and leaf blade colour intensity, were used to assess vine nitrogen status. All of the three indicators of vine water status allowed a clear differentiation of vine water uptake conditions in the ten experimental plots. The indicators of vine nitrogen status showed more ambiguous results. Must assimilable nitrogen content did not only vary with vine nitrogen uptake, but also with yield. Leaf colour was more easy to interpret. Vine development and berry composition were more influenced by water uptake conditions than by vine nitrogen status. In 2000, which was a dry vintage in Bordeaux, water stress induced early growth slackening and a small berry size. Grapes contained more sugar, anthocyanin and total phenolics and less malic acid when water availability was low. On plots where water uptake conditions were similar, low vine nitrogen status increased berry potential.