Fishman, S., Department of Statistics and Operations Research, ARO, Volcani Center, 50250 Bet Dagan, Israel
Génard, M., Unité de Recherche en Ecophysiolögie et Horticulture, INRA, Domaine Saint-Paul, Site Agroparc, 84914 Avignon Cedex 9, France

A model of fruit growth was developed which describes a coupled accumulation of water and dry matter. It focused on the final stage of fruit development, when cell division is finished and the relationships between the basic mechanisms may be represented in a relatively simple way. The model was applied to calculation of seasonal and diurnal growth of the peach [Prunus persica (L.) Batsch] fruit, but it could be parametrized and calibrated for other fleshy fruits. The movement of water and photosynthates across a set of transport barriers, arranged both in series and in parallel, was approximated by the movement across one barrier with combined transport characteristics. Thus, the fruit was considered as one compartment, separated from two external compartments - the parent plant and the ambient atmosphere - by composite membranes. The relative humidity and temperature of the ambient atmosphere, the water potential in the stem and the concentration of sugars in the phloem were used as input variables for the model computations. In parallel with the main dynamic variables - dry and fresh masses of fruit - the auxiliary variables were calculated as functions of the external conditions; they were the water content, sugar concentration, and hydrostatic and osmotic pressures in the fruit.