INTRODUCTION

Some fruits show reversible shrinkage on a daily basis directly linked to their water balance. The recognized interpretation of this process based on a reverse flux of water from the fruit to the plant in response to the transpirational pull of the foliage (Kozlowski, 1972, 1982) is similar to that used to explain diurnal trunk shrinkage (Landsberg, Blanchard & Warrit, 1976; Powell & Thorpe, 1977). This interpretation based on a network of hydraulic resistances and capacitances, and a single water flux between “bark” and xylem (Fig. 5A) gives a good explanation of the time lag between xylem water potential and trunk shrinkage. Our results show that for fruits, the model of reverse flux between fruit and xylem stem is not valid particulary because it cannot explain the delay between fruit shrinkage and changes in xylem water potential.

MATERIALS AND METHODS

Experimental site and plant material

The experiment was carried out in a five-year-old peach orchard (Prunus persica L. cv. Fire-Red on GF 305 rootstock). This old variety was chosen because the growing curve of the fruit presents 3 stages (stage I, until end of May: high growth rate; stage II, from beginning of June to mid-July: slow growth rate; stage HI, from mid-July to mid-August: high growth rate).