Variation in surface conductance to water vapor diffusion in peach fruit and its effects on fruit growth assessed by a simulation model

Surface conductance to water vapor diffusion was measured in individual pea ch fruits (Prunus persica (L.) Batsch) and plotted as a function of fresh f ruit mass for four cultivars. Surface conductance increased with fresh frui t mass, but the pattern differed with cultivar, and fruit-to-fruit variatio n occurred. Relationships between fruit mass and surface conductance were m odeled by fitting mathematical equations to the data. The simulation model of Fishman and Genard (1998) was used to study dry mass and water component s of fruit growth (1) when surface conductance varied with fruit size or wa s constant, and (2) when surface conductance values were high, moderate or low with respect to fruit mass. Increased surface conductance with fresh fr uit mass resulted in fruit growth cessation. Fruits differing in surface co nductance had similar dry mass. However, under well-watered conditions (ste m water potential between -1 and -0.2 MPa), the water balance components of growth (osmotic and hydrostatic pressure, water potential and water balanc e) differed greatly and, as a result, the lower the surface conductance the greater the fresh fruit mass. These differences were buffered under drough t conditions (stem water potential between -2.4 and -0.6 MPa).