Linking water stress effects on carbon partitioning by introducing a xylem circuit into L-PEACH.

BACKGROUND AND AIMS Many physiological processes such as photosynthesis, respiration and transpiration can be strongly influenced by the diurnal patterns of within-tree water potential. Despite numerous experiments showing the effect of water potential on fruit-tree development and growth, there are very few models combining carbohydrate allocation with water transport. The aim of this work was to include a xylem circuit into the functional-structural L-PEACH model. METHODS The xylem modelling was based on an electrical circuit analogy and the Hagen-Poisseuille law for hydraulic conductance. Sub-models for leaf transpiration, soil water potential and the soil-plant interface were also incorporated to provide the driving force and pathway for water flow. The model was assessed by comparing model outputs to field measurements and published knowledge. KEY RESULTS The model was able to simulate both the water uptake over a season and the effect of different irrigation treatments on tree development, growth and fruit yield. CONCLUSIONS This work opens the way to a new field of modelling where complex interactions between water transport, carbohydrate allocation and physiological functions can be simulated at the organ level and describe functioning and behaviour at the tree scale.