@article {Poni71, author = {S. Poni and C. Intrieri and O. Silvestroni}, title = {Interactions of Leaf Age, Fruiting, and Exogenous Cytokinins in Sangiovese Grapevines Under Non-Irrigated Conditions. I. Gas Exchange}, volume = {45}, number = {1}, pages = {71--78}, year = {1994}, doi = {10.5344/ajev.1994.45.1.71}, publisher = {American Journal of Enology and Viticulture}, abstract = {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.}, issn = {0002-9254}, URL = {https://www.ajevonline.org/content/45/1/71}, eprint = {https://www.ajevonline.org/content/45/1/71.full.pdf}, journal = {American Journal of Enology and Viticulture} }