Diurnal and Spatial Variation in Leaf Water Potential and Leaf Conductance of Irrigated Peach Trees

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Abstract
Leaf water potential, conductance and relative water content were measured in three layers of the canopy of large peach trees during imgation cycles. In the top layer, leaf water potential decreased from early morning until the early afternoon reaching values ranging from about -1.8 MPa soon after irrigation to -2 5 MPa at the end of a drying cycle; leaf conductance (mean about 0.42 cm s-1) decreased slightly during this period but did not appear to be influenced by water potential at values higher than about - 1 .9 MPa. From early afternoon to late evening, leaf conductance continued to decrease and water potential increased. Similar cycles were noted in the middle and lower layers except that water potential was always higher and conductance lower. A high degree of exposure of leaves to insolation appeared to result in low potentials and high conductances. The adequacy of current imgation recommendations for high productivity is discussed.