Automatic plant-based water status monitoring in grapevine using an improved water transport and storage model

As all plants, grapevines (Vitis vinifera L.) need water to function properly. A certain level of drought stress might however be beneficial as it improves the composition of the grape. Earlier research has shown that differences in water status result in wines with different appearance, aroma, flavour and colour. Nevertheless, the level and timing is of utmost importance. Therefore, an adequate monitoring of the water status is crucial for improving grape (and wine) quality. It is internationally recognised that this should be based on plant measurements, because only then information is gained about the actual plant water status. Mechanistic models are promising for this purpose and allow a deeper understanding of the underlying mechanisms. In this study we use a dynamic water transport and storage model that links sap flow, or whole plant water consumption, and stem diameter variations in order to simulate stem water potential. This variable is considered as one of the best indicators for water status. We aimed at improving the model to perform well under both wet and pronounced dry conditions and evaluated it for real-time water status monitoring. To this end, the former constant flow resistance in the xylem has been replaced by a dynamic resistance depending on measured soil water potential and combines the resistance experienced in the soil, roots and stem. Furthermore, also the radial flow resistance (between xylem and storage tissues), originally implemented as a constant value, has been replaced by an equation. The improved model is able to accurately simulate the plant water status during both wet and pronounced dry conditions. The model seems very promising to apply as an automatic plant-based water status monitoring system and may be a tool to improve grape and wine quality