Abstract
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.
Highlights
With photosynthesis (Heuvel et al, 2002)
Infiltration of sucrose in barley leaf in the dark found post-translational activation of the nitrate reductase enzyme, suggesting that the link between photosynthesis and nitrogen metabolism goes through the presence of carbohydrates (Provan and Lillo, 1999)
By other side, during this time, there was not recorded changes in the stomatal conductances and it is possible to observe that the photosynthetic active radiation was even higher in the case of the palatinose treated leaves
Summary
With photosynthesis (Heuvel et al, 2002). it is known that an accumulation of carbohydrate in leaves, The translocation of photosynthates from the leaf is the phenomena underlying the accumulation of sugars in the berry at post-veraison as shown by the higher activity of phloem at this stage (Greenspan et al, 1996) and by experiments in which the phloem disruption brings about an accumulation of sucrose in leaf (Hunter and Ruffner, 2001). Tiznado-Hernandez, M.E. et al / American Journal of Agricultural and Biological Sciences 8 (1): 28-33, 2013 concentration giving rise to differences in water potential within the phloem and between the phloem and the fruit regulates the speed of sugar accumulation in the berry (Coombe, 1992; Kuhn et al, 1999). There are very few reports with the objective of increasing the accumulation speed of sugar in berry It was reported the use of poly carboxylic acids (BasilioHeredia, 1998) and a mixture of gibberelic acid, ascorbic acid and sucrose (Tomer and Kumar, 1977). In both of them, the treatments failed to get an increase in the speed of sugar accumulation in berry. The induction of an active synthesis of organic nitrogen in these plants by the presence of sucrose in leaf further supports the statement that an active translocation to the sink was taking place since it had been found that the translocation of sucrose to a growing fruit usually goes along with the active synthesis of aminoacids (Paul and Froyer, 2001)
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