Variations in the orchard environmental conditions affect vascular and transpiration flows to/from peach fruit

Temperature, relative humidity and light are important environmental parameters affecting whole tree development and performances, either at leaf and fruit level. In this study, the effect of different environmental conditions resulting from conditioning the light environment in the orchard were tested on peach fruit growth and quality over two seasons. The first year work was carried out on the mid-season 'Red Gold' nectarine, by applying Extenday® reflective mulches; the second year, Extenday® and black shading nets were applied on trees of the early season 'Alice-col'. In both seasons, daily growth rate, vascular and transpiration flows were measured on four-five fruit per treatment during the cell expansion stage. Phloem, xylem and transpiration flows were estimated by continuous monitoring of fruit diameter by automatic, custom-built fruit gauges. At harvest fruit size, soluble solids content and dry matter percentage were measured. Extenday® mulches increased and shading nets decreased the orchard VPD, thus causing higher fruit transpiration in Extenday® fruit, during the second, but not during the first year. Phloem and xylem flows increased with the use of reflective mulches but were reduced by shading. A lower amount of carbohydrates received via phloem by shaded fruit may explain their lower mean size, soluble solids content and dry matter percentage at harvest. Daily xylem and phloem inflows were both positively related to fruit water losses during both seasons. These relationships suggests a positive role of fruit transpiration in peach growth, as water losses decrease fruit water potential and increase the gradient needed for xylem flow and for bulk flow phloem unloading. Differences in canopy light conditions among treatments probably affected whole tree carbon assimilation and the amount of resources available for the growing sinks. This may have concurred in enhancing the differences in fruit growth and quality among treatments. © ISHS 2012.