Frutto di pesco: dinamica giornaliera di accrescimento. ITALUS HORTUS,

The relative contributions of xylem, phloem and transpiration to fruit growth and the daily patterns of their flows have been determined in peach during the two stages of rapid diameter increase by precise and continuous monitoring of fruit diameter variations. Xylem, phloem and transpiration contributions to growth were quantified by comparing the diurnal patterns of diameter change of fruits which were subsequently girdled and detached. Xylem supports 70% and phloem 30% of peach growth , while transpiration represents about 60% of daily total inflows. These figures and their diurnal patterns were comparable among years, stages and cultivars. The xylem was functional both at stage I and III, while fruit transpiration was high and strictly dependent on environmental conditions, causing periods of fruit shrinkage. Phloem imports were correlated to fruit shrinkage and appear to facilitate subsequent fruit enlargement. Peach displays a growth mechanism which can be explained on the basis of passive unloading of photoassimilates from the phloem. A pivotal role is played by the large amount of water flowing from the tree to the fruit and from the fruit to the atmosphere.