Effect of girdling on gas exchanges and leaf mineral content in the "independence" nectarine

The aim of this work was to analyze the physiological modifications induced by girdling, and to evaluate their effects on the gas exchanges and mobili ty of the mineral elements in peach leaves. On 15 trees, sixty 1-yr-old sho ots were chosen, thirty of which were girdled (a ring of bark 1 cm thick wa s removed), and 30 were used as control. The fruits were removed from half the girdled shoots and from the same number of control shoots. The followin g data were taken from all shoots: measurements of gas exchanges, analysis of leaf mineral content, analysis of leaf and shoot characteristics, analys is of fruit characteristics. In the girdled shoots a reduction in their dev elopment, an improvement in fruit quality and earlier ripening was noted. G irdling, breaking off the phloematic flow, causes a store of elaborated sap in the portion of the shoot over the girdling that inhibits the photosynth etic activity of the leaves. On the girdled shoots the presence of fruit, w hich is a sink for nutritive elements, promotes photosynthesis and transpir ation. Transpiration and the stole of mineral elements [nitrogen (N), phosp horus (P), potassium (K), calcium (Ca, and magnesium (Mg)] in the leaves ap peared closely connected. Indeed after a reduction in the transpiration rat e of the leaves of the girdled shoots, there was a decrease in the store of all the mineral elements analyzed. Our observations confirmed the check of gas exchanges due to girdling and due to the presence of fruit, and show t hat girdling has a clear effect on the nutritional state of the leaves.