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- Effects of irrigation and collection period on grapevine leaf (Vitis vinifera L. var. Touriga Nacional): Evaluation of the phytochemical composition and antioxidant propertiesPublication . Barreales, David; Malheiro, Ricardo; Pereira, J.A.; Andrade, João Verdial; Bento, Albino; Casquero, Pedro Antonio; Ribeiro, A.C.The cultivation of grapevines (Vitis vinifera L.) has extended worldwide, with great economic importance. From this crop, we can obtain grapes for fresh consumption, raisins, juices, wine, and other derived products. The cultivation of grapevines also generates some byproducts, such as seeds, skins, wood and leaves. The leaves can be removed from the plant, as is common agricultural practice, to improve the production and quality of the grapes at certain periods in the crop cycle. In the present work, the phytochemical composition (total phenols content, hydroxycinnamic acids derivatives and flavonols) and antioxidant potential (reducing power, ABTS and DPPH radical scavenging capacity) of grapevine leaves from cv. Touriga Nacional were evaluated. The studied cultivar was under three severities of regulated deficit irrigation (RDI60, RDI40, and RDI20; providing 60, 40 and 20% of reference evapotranspiration, respectively) and non-irrigation (NI; exclusively rain-fed), in a vineyard located in the Demarcated Douro Region (Portugal). The leaves were collected at three different phenological stages: veraison, maturation, and grape harvest. For the first time, the interactions between different irrigation regimes and the collection period were evaluated on grapevine leaves. The results obtained for the phytochemical composition revealed that increasing irrigation reduced total phenols content, hydroxycinnamic acids derivatives, and flavonols in all of the phenological stages studied. For instance, compared to that of the control treatment (NI), the total phenols content reduced 19% in RDI20 (from 189 mg GAE g−1 to 153 mg GAE g−1), 28% in RDI40 (136 mg GAE g−1), and 33% in RDI60 (127 mg GAE g−1). The antioxidant activity suffered a reduction when the irrigation amount was increased for all assays. Additionally, the antioxidant activity suffered a reduction over time, presenting higher values in veraison. For harvest sampling, the loss of antioxidant activity was more notable, with EC50 values varying between 0.092 mg mL−1 (NI) and 0.187 mg mL−1 (RDI60). Altogether, the results suggest that grapevine leaves are a potential source of natural compounds with valuable antioxidant properties that could be explored by the pharmaceutical, chemical and food industries.
- Response of grapevine CV. “Tinta roriz” (Vitis vinifera L.) to moderate irrigation in the Douro Region, PortugalPublication . Ribeiro, A.C.; Andrade, João VerdialThe behaviour of cv. “Tinta Roriz” (Vitis vinifera L.), was studied when moderate drip irrigation was applied from veraison to harvest. Field studies were conducted during three growing seasons (2006-2008) in a commercial vineyard located in the Douro region, Portugal. Experimental layout consisted in the measurement of physiological and agronomic parameters in vines submitted to three different irrigation treatments: 0R was non-irrigation, 2R and 4R were irrigated with a constant fraction of reference evapotranspiration of 0.2 and 0.4, respectively. The results showed that moderate irrigation improved plant water status, leaf photosynthesis and transpiration. Yield components and pruning weights had a significant increase, only in the 2008 growing season, in 4R irrigated treatment. There were no significant differences between treatments in the accumulation of sugar, titratable acidity and pH in berries. The total phenols and the colour intensity showed a tendency, not significant, to decrease in irrigated treatments.
- Response of grapevive CV. “Tinta Roriz (Vitis vinifera L. ) to moderate Irrigation in the Douro Region, PortugalPublication . Ribeiro, A.C.; Andrade, João VerdialThe behaviour of cv. “Tinta Roriz” (Vitis vinifera L.), was studied when moderate drip irrigation was applied from veraison to harvest. Field studies were conducted during three growing seasons (2006-2008) in a commercial vineyard located in the Douro region, Portugal. Experimental layout consisted in the measurement of physiological and agronomic parameters in vines submitted to three different irrigation treatments: 0R was non-irrigation, 2R and 4R were irrigated with a constant fraction of reference evapotranspiration of 0.2 and 0.4, respectively. The results showed that moderate irrigation improved plant water status, leaf photosynthesis and transpiration. Yield components and pruning weights had a significant increase, only in the 2008 growing season, in 4R irrigated treatment. There were no significant differences between treatments in the accumulation of sugar, titratable acidity and pH in berries. The total phenols and the colour intensity showed a tendency, not significant, to decrease in irrigated treatments.