Seasonal dry matter production in field-grown sangiovese and montepulciano grapevines (Vitis vinifera L.)

Seasonal dry matter production of Vitis vinifera 'Sangiovese' and 'Montepulciano' cultivars was studied via destructive measurements in the field and by modeling daily carbon supply per vine. Carbon supply was obtained from the daily balance between photosynthesis and respiration rate, and accumulated as dry matter. The daily photosynthetic integral per vine was estimated from maximum net photosynthetic rate, photochemical efficiency, daily integral of light, day-length, canopy extinction coefficient and intercepted light. The daily respiration rate was estimated from the respiration rate and the dimension of the different organs (shoots, leaves, clusters). The trials were conducted in central Italy (Marche and Umbria), on spurpruned and cordon-trained vines. Maximum photosynthetic rate and photochemical efficiency measurements showed that Montepulciano vines were more drought and high temperature tolerant in midsummer than Sangiovese vines, which had the highest photosynthetic efficiency under cooler temperatures in the first part of the growing season. After harvest, both cultivars showed similar photosynthetic behavior. All vine organs showed high respiration rate during the initial growth period. In Sangiovese, seasonal canopy dry matter accumulation, modeled by Stella software, fitted well to the effective dry weight accumulation obtained from destructive measures up to pre-harvest. Successively, the modeled supply increasingly exceeded the demand, thus allowing accumulation of reserves in old wood and roots. The seasonal dry matter production of grapevine can only be properly modeled through accurate measurements of photosynthetic efficiency and maximum photosynthetic rate, because their seasonal pattern during typical dry, warm Mediterranean summers is strongly variety-dependent and variety-specific. © ISHS.