RT Journal Article SR Electronic T1 Interactions of Leaf Age, Fruiting, and Exogenous Cytokinins in Sangiovese Grapevines Under Non-Irrigated Conditions. I. Gas Exchange JF American Journal of Enology and Viticulture JO Am J Enol Vitic. FD American Society for Enology and Viticulture SP 71 OP 78 DO 10.5344/ajev.1994.45.1.71 VO 45 IS 1 A1 S. Poni A1 C. Intrieri A1 O. Silvestroni YR 1994 UL http://www.ajevonline.org/content/45/1/71.abstract AB The interactions of leaf age and gas exchange, together with modifications induced by fruiting and exogenous kinetin treatments, were investigated in field-grown Sangiovese (Vitis vinifera L.) grapevines. Analyses carried out both on a seasonal basis and within each sampling date as a function of the natural gradient of age along the shoot showed that maximum Pn occurred at 30 to 35 days of age. A progressive decline started at about 50 days and four-month-old leaves retained 45% of maximum Pn. Very young, rapidly expanding leaves (< 15 days) also showed a consistently lower Pn and water use efficiency (WUE) than recently fully expanded leaves. Differential rates of leaf senescence due to fruiting or kinetin were not observed. These data form a basis for improving the physiological understanding of widely used vineyard management operations (shoot topping, leaf removal) which normally induce variations in canopy leaf age.