Manipulation of Photosynthesis in Grape (Vitis vinifera) CV. ‘Flame’ by the Application of Two Sucrose Analogs

The translocation of photosynthates from the leaves is important for the accumulation of sugars in grape berries. Two sucrose analogs were applied at post-veraison to determine their effects on leaf photosynthesis. It is hypothesized that the signal of sugar accumulation in leaves will bring a reduction in photosynthesis and an increase in the photosynthate translocation rate to the berries. The experiment was conducted in a commercial Vitis vinifera ‘Flame’ vineyard. The sucrose analogs used were palatinose and turanose at 5 mM. For each treatment, five fully expanded leaves from five different vines were sprayed until run-off. Control leaves were treated with distilled water. Net photosynthesis rate (Pn), stomatal conductance (gs), Photosynthetically Active Radiation (PAR) and leaf temperature (Lt) were measured at 0, 10, 20, 30, 60 and 90 min after the treatment with a LICOR-6200 portable photosynthesis system. Statistical analysis was made by variance analysis based on a randomized complete block design and means separated using the Student-Newman-Keuls test with a confidence level of 0.05. The application of turanose did not affect Pn whereas palatinose reduced the Pn one hour after application. At this point, not statistical differences were found in gs and PAR. It was concluded that the application of palatinose can reduce the net photosynthesis which suggests that it is possible to manipulate photosynthesis by the utilization of sucrose analogs which maybe also increases the translocation of photosynthates from grape leaves to grape berries.