Water dynamics of Touriga-Nacional grapevines trained in cordon and guyot systems under Mediterranean climate conditions

Aims: The aims of the present study were to (1) evaluate the water dynamics of Touriga-Nacional grapevines trained to spur pruned cordon and Guyot systems and (2) assess the effect of variable water availability in a commercial vineyard located in the Demarcated Douro Region (DDR), Portugal.

Methods and Results: The study was carried out in a commercial vineyard, located in the Upper Douro sub-region (the eastern sub-region with harsher climatic conditions) of the DDR. The climate of this area is typically Mediterranean and the soil of schist origin. Touriga-Nacional grapevines grafted onto 110 Richter rootstocks trained to spur pruned cordon and Guyot systems were selected. Sap flow and trunk diameter measurements were performed during the growing season. Complementarily, soil moisture, leaf water potential and leaf area index measurements were made. The results showed daily trunk diameter fluctuations (TDFs), with the contraction, recovery and increment phases and higher sap flow (SF) rates at earlier stage. Under harsh pedoclimatic conditions, SF was reduced and TDF flattened. Rehydration and stomatal mechanisms were mostly associated with these responses. Furthermore, Guyot-trained vines showed higher changes in TDF for the same SF values, where TDF of spur pruned cordon-vines remained practically unchanged over maturation. These results pointed to the effect of the shorter length of the hydraulic pathways of the Guyot-trained vines, in comparison with the cordon-trained vines.

Conclusions:

The study exposed the daily and seasonal water dynamics and crop performance of mature vines over the growing season, highlighting the adaptive potential of the Guyot training system to the DDR. The use of plant-based measurement sensors (sap flow and trunk diameter sensors) revealed sensitivity to irrigation (and precipitation) events and conditions of significant atmospheric evaporative demand.

Significance and Impact of the Study: Adaptation strategies to climate variability and climate change must be adopted to maintain grapevine yield and quality in order to guarantee economic and environmental sustainability. The adequate selection of the grapevine training system and improved water-use efficiency stand out as one of the most critical for the present and future times