Cessation of berry growth coincides with leaf complete stomatal closure at pre-veraison for grapevine (Vitis vinifera) subjected to progressive drought stress

Abstract

Background and Aims Drought events have devasting impacts on grape berry production. The aim of this study was to investigate berry growth in the context of leaf stomatal closure under progressive drought stress. Methods Potted grapevine plants (variety ‘Syrah’ and ‘Cabernet Sauvignon’) were evaluated at pre-verasion (berry growth stage 1, 30-34 days after anthesis, DAA) and post-veraison (late berry growth stage 3, 90 to 115 DAA). Berry diameter, berry absolute growth rate (AGR), leaf stomatal conductance (Gs) at midday, plant water potential at midday and predawn (⎕PD and ⎕MD, respectively), and soil relative water content was measured repeatedly. The ⎕PD-threshold of 90% loss in stomatal conductance (Gs10) was determined and referred to as complete stomatal closure. Data were interpreted in the context of plant dehydration phases and associated boundary ⎕1 obtained from the relationship of ⎕PD and ⎕MD (i.e. water potential curve). Key Results At pre-veraison, berry AGR declined together with leaf Gs in response to soil drying in both varieties. Berry AGR transitioned from positive to negative (shrinkage) values when leaf Gs approached zero (i.e. 0.011 and 0.018 mol s -1 m -2 in ‘Syrah’ and ‘Cabernet Sauvignon’, respectively). These Gs values corresponded to Gs10 of -0.81 in ‘Syrah’ and -0.74MPa in ‘Cabernet Sauvignon’. At post-veraison, berry AGR was negligible and negative AGR values were not intensified by increasing drought stress in both varieties. Conclusion Leaf complete stomatal closure under progressive drought stress coincides with cessation of berry growth followed by berry shrinkage at pre-veraison (growth stage 1).