Physiological Response of Crimson Seedless Table Grape Vines to Controlled Irrigation Conditions in Different Micro-Climatic Environments

Producing table grapes in altered environments requires an understanding of grapevine physiological responses. This study aimed to determine the physiological reactions of Crimson Seedless/Ramsey vines in response to different water application levels in different micro-climates. Irrigation treatments entailing 100% (W100 = control), 80% (W080), 70% (W070), and 55% (W055) of control volumes were applied to open field (OF) vines and vines underneath overhead plastic covering (OPC). Soil water content (SWC), net photosynthesis (Pn), stem water potential (Ψ_S), transpiration (Tr), micro-climatic variables, and leaf area were measured. The W080 and W070 treatments for OF and OPC, respectively, did not impair physiological processes compared to W100. Conversely, W055 significantly decreased Ψ_S, Pn, and Tr in both trials compared to W100. Underneath OPC, SWC, leaf area, Pn, and Tr values were higher than under OF conditions. Compared to OF, OPC decreased light intensity and increased Ψ_S, albeit resulting in lower photosynthetic water use efficiency. Vines receiving W070 and W055 experienced less stress underneath OPC than under OF conditions, indicating that OPC improves response to water deficit conditions. Additionally, W055 under OPC lowered the average air temperature compared to OF. Water supply reductions of 20% under OF conditions and 30% underneath OPC sufficiently maintained physiological processes.