Exploring the plasticity of the grapevine drought physiology

Abstract

Context and purpose of the study ‐ Grapevine response to water deficit has been extensively studied. Nevertheless, debate still exists regarding some physiology adoption under drought, e.g. vulnerability to cavitation or iso‐anisohydric classification, among others. Discrepancies between published results, other than specific experimental setup, are attributed to environment/climate conditions and genotypes used. Indeed, the same genotype could exhibit a different phenotype under different climates (i.e. phenotypic plasticity). To date little information is available regarding the plasticity extent of certain traits related to drought response in grapevines. Here we present the results of a novel experiment, where a single genotype was exposed to similar water stress conditions in two different locations characterized by different climatic conditions.

Material and methods ‐ 90 plants of Grüner Veltliner grafted on 5BB rootstock were grown in pots during the 2016 season in Tulln (N‐E Austria). In January 2017 and after pruning, half of the vines were transported to Udine (N‐E Italy). In both locations, vines were re‐potted in 20L pots and filled with the same commercial potting media supplemented with 30% perlite. Then, pots were arranged in rows that were covered using a plastic film roof to prevent rain. Water was supplemented by drip irrigation and a set of vines were positioned under weighting mini‐lysimeters to measure ETc. Climate data was recorded by a weather station in each site. Vines were irrigated daily to 100% ETc until the imposition of water stress (WS) towards the end of June (pre‐veraison, E‐L 33). WS vines were daily irrigated 30% ETc of WW, ecophysiological data recorded frequently, and berry/leaf tissues sampled. The experiment was carried out for two consecutive vintages on the same vines.

Results ‐ Climatic variables were different between sites and deficit irrigation based on ETc yielded different results in terms of water stress intensity. In both years, well‐watered controls in Tulln never reached water potential below ‐0.7 MPa while those in Udine reached values as low as ‐1.2 MPa. Although the pot volumes and soil type used was the same, differences in atmospheric water demand determined different irrigation volumes between sites. Also, WS vines in Udine reached Ψstem values much lower than in Tulln, impacting differently as well some berry ripening parameters. Interestingly, the stomatal conductance (gs) response to Ψstem was different between sites: in Udine gs reached values <50 mmol H2O m‐2 s‐2 at Ψstem values much lower (‐1.2 MPa) than in Tulln (‐0.8 MPa), showing how gs/Ψ often used as indicators for iso‐anisohydric classification are influenced by environmental conditions. Finally, the WUEi was different among sites in 2018, determining a better performance of the vines in Tulln compared with those in Udine.