USING SWAF, A GENERIC BIOPHYSICAL MODEL OF SUGAR AND WATER ACCUMULATION TO ANALYZE FRUIT DEVELOPMENT

The SWAF (Sugar and Water Accumulation in the Fruit) model is based on the biophysical representation of water and sugar transport combined with the growth process stimulated by turgor pressure. Fruit flesh is described as one compartment separated from the atmosphere and parent plant by membranes. The parent plant supplies the fruit with water and sugars which are brought through xylem vessels and phloem sieve tubes. The fruit consumes sugars and water through the respiration and transpiration processes. Variation in elastic fruit growth was modeled as a function of the elastic modulus and variation in turgor pressure. Variation in plastic fruit growth was modeled as a function of turgor pressure using the Lockhart (1965) equation. The hourly inputs of the model are temperature and relative humidity of the ambient atmosphere, water potential in xylem vessels, and sugar concentration in the phloem sap. The model fits fruit growth well for species as contrasted as peach, tomato, mango and grape. The model was used to analyse the variations in the main processes involved in fruit growth in response to carbon and water stresses. The conclusions are that this model is able to simulate the complex fruit behaviour in response to external or internal factors and may be a powerful tool to analyse fruit development.