The effect of extreme water stress on leaf drying limits and possibilities of recovering in three grapevine (Vitis vinifera L.) cultivars

This study was conducted in three grapevine cultivars (cv. Chardonnay, Merlot and Cabernet-Sauvignon) vines during the 2009 growing season in the ECOTRON of the campus of Montpellier SupAgro/France. The aim of this research was to analyze the effect of sudden and extreme water stress (EWS) to determine the limit of the leaf drying (depend on. leaf), possibilities of recovering, and its relationship with grapes composition. A randomized block design was used. There were three blocks with three replicates. In the experiment all plots consisted of totally 36 grapevines. During the entire experiment in ESW vines both psi(pd) and psi(md) values were close to each other by decreasing to about -2.1 MPa in all three varieties. After this level (-2.1 MPa) they both get close to each other until their equality in -3.7 MPa. This value was determined as the threshold of all leaf dryings in the vines. In EWS vines the lowest read psi(pd) and psi(md) was -4.6 MPa. In the next measurement psi(pd) and psi(md) were forced to -5.0 MPa, and water exit from leaf petiole was not observed in the same vines. After EWS treatment, berries became smaller and these lead to increase of Anthocyanin concentration, Folin-Ciocalteu index (FCI) and PTI values at harvest time. However as a result of EWS applications pH values increased to a level which had a negative effect on wine quality. There was a reduction in the values of 100 berry weight, berry volume, total soluble solids (TSS), sugar concentration, sugar content per berry, K and tartaric acid. The conclusion is that as a result of sudden EWS although all the leaves dried, vines did not die even they recovered by rewatering. However EWS had a negative effect on the berry quality