Movement of photosynthates and water to fruit

A model of fruit growth was developed which describes a coupled accumulatio n of water and dry matter. It focused on the final stage of fruit developme nt, when cell division is finished and the relationships between the basic mechanisms may be represented in a relatively simple way. The model was app lied to calculation of seasonal and diurnal growth Of the peach [Prunus per sica (L.) Batsch] fruit, but it could be parametrized and calibrated for ot her fleshy fruits. The movement of water and photosynthates across a set of transport barriers, arranged both in series and in parallel, was approxima ted by the movement across one barrier with combined transport characterist ics. Thus, the fruit was considered as one compartment, separated from two external compartments - the parent plant and the ambient atmosphere - by co mposite membranes. The relative humidity and temperature of the ambient atm osphere, the water potential in the stem and the concentration of sugars in the phloem were used as input variables for the model computations. In par allel with the main dynamic variables dry and fresh masses of fruit the aux iliary variables were calculated as functions of the external conditions; t hey were the water content, sugar concentration, and hydrostatic and osmoti c pressures in the fruit.