Photosynthetic capacity and carbon partitioning in water stressed carmenere grapevines

Abstract

Even though convenient for grape berry quality for wine making in grapevines, water stress is known to provoke negative physiological effects on plants. In grapevines, however, besides the reduced carbon source capacity, water restriction also leads to a transiently increased demand at the grape berry level. We have investigated the effect of different water supplies along the season in 12 years old commercial Carmenere vines, North to South oriented in a vertical trellising system, in the Maipo Valley in Chile, in order to assess the leaf to berry matching capacity for carbon allocation, sugar unloading and accumulation in  berries. 200L (T1), 410 L (T2), 850 L (T3) and 1500 L (T4) of water were supplied to grapevine plants in the field, along the season, from nearly one week before veraison until harvest. Significant differences in carbon gain were observed between treatments. Source capacity in T1 seems to be high enough for phloem loading since starch content, as well as reducing sugars, along the day and season, were higher than T4, in the East and West side of the canopy. As for grape berries, T2 and T3 resulted in higher glucose, fructose and sucrose concentration, suggesting that a simple model correlating source and sink strength to the resulting starch accumulation in leaves is not applicable in field systems.