Browsing by Author "Rodrigues, M.L."
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- Acclimation to short-term low temperatures in two Eucalyptus globulus clones with contrasting drought resistancePublication . Silva, F.Costa e; Shvaleva, A.; Broetto, F.; Ortuño, M.F.; Rodrigues, M.L.; Almeida, M.H.; Chaves, M.M.; Pereira, J.S.We tested the hypothesis that Eucalyptus globulus Labill. genotypes that are more resistant to dry environments might also exhibit higher cold tolerances than drought-sensitive plants. The effect of low temperatures was evaluated in acclimated and unacclimated ramets of a drought-resistant clone (CN5) and a drought-sensitive clone (ST51) of E. globulus. We studied the plants’ response via leaf gas exchanges, leaf water and osmotic potentials, concentrations of soluble sugars, several antioxidant enzymes and leaf electrolyte leakage. Progressively lowering air temperatures (from 24/16 to 10/ 2 C, day/night) led to acclimation of both clones. Acclimated ramets exhibited higher photosynthetic rates, stomatal conductances and lower membrane relative injuries when compared to unacclimated ramets. Moreover, low temperatures led to significant increases of soluble sugars and antioxidant enzymes activity (glutathione reductase, ascorbate peroxidase and superoxide dismutases) of both clones in comparison to plants grown at control temperature (24/16 C). On the other hand, none of the clones, either acclimated or not, exhibited signs of photoinhibition under low temperatures and moderate light. The main differences in the responses to low temperatures between the two clones resulted mainly from differences in carbon metabolism, including a higher accumulation of soluble sugars in the drought-resistant clone CN5 as well as a higher capacity for osmotic regulation, as compared to the droughtsensitive clone ST51. Although membrane injury data suggested that both clones had the same inherent freezing tolerance before and after cold acclimation, the results also support the hypothesis that the droughtresistant clone had a greater cold tolerance at intermediate levels of acclimation than the drought-sensitive clone. A higher capacity to acclimate in a short period can allow a clone to maintain an undamaged leaf surface area along sudden frost events, increasing growth
- An attempt to quantify grapevine water stress in a mediterranean environmentPublication . Lopes, C.M.; Vicente-Paulo, J.; Santos, T.; Rodrigues, M.L.; Barroso, J.; Chaves, M.M.Aiming to quantify the effects of the intensity and duration of grapevine water stress, physiological and agronomical data from an irrigation experiment conducted during 1999 at Alentejo, south of Portugal, with the red variety Aragonez (syn. Tempranillo) were correlated with an water stress index (Sψ). This index was calculated by the integral of predawn leaf water potential below –0.2 MPa between bloom and harvest. Significant relationships were found between the Sψ, yield components and berry composition. The multiple regression analysis shows that the Sψ in the period bloom-veraison has a higher contribution to explain the variation in berry weight, anthocyanins and phenolics concentration than the Sψ in the period veraison-harvest. The knowledge of those relationships, together with the relationship between available soil water content and predawn leaf water potential, may allow the adequate management of soil water availability to optimise the yield/quality ratio for each ecological situation
- Deficit irrigation in Mediterranean environment. What lessons have we learnt from grapevine studies ?Publication . Chaves, M.M.; Zarrouk, O.; Francisco, R.; Costa, J. M.; Santos, T.; Regalado, A.P.; Rodrigues, M.L.; Lopes, CarlosDeficit irrigation techniques, implying that water is supplied at levels below full crop evapotranspiration throughout the growing season or in specific phenological stages, such as regulated deficit irrigation (RDI) or partial root drying (PRD), emerged as potential strategies to increase water savings with marginal decreases of yield and likely positive impact on fruit quality. Understanding the physiological and molecular bases for plant responses to mild to moderate water deficits is of utmost importance to modulate the appropriate balance between vegetative and reproductive development, to improve crop water-use efficiency and to control fruit quality. It is acknowledged that the timing and intensity of the response to soil and atmospheric water deficits, namely in what concerns stomatal control, depends greatly on the genotype. This has profound implications in irrigation management, in particular the timing and amount of irrigation to optimize source-sink relationships and achieve optimal fruit quality in each variety. Mild water deficits also exert direct and/or indirect (via the light environment in the cluster zone) effects on berry development and composition. A current research challenge is determining how the environment, in particular water deficits, regulates genes and proteins of the various metabolic pathways responsible for berry composition and therefore for wine quality
- Deficit irrigation in Mediterranean vineyards - a tool to increase water use efficiency and to control grapevine and berry growthPublication . Costa, J. M.; Lopes, Carlos; Rodrigues, M.L.; Santos, T.P.; Francisco, R.; Zarrouk, O.; Regalado, A.; Chaves, M.M.Water is increasingly scarce in Mediterranean Europe and irrigated agriculture is one of the largest and most inefficient users of this natural resource. Ecological topics such as the “water foot print” have become more relevant for the academy, consumers, governments and food industry. The wine sector needs solutions to improve its economical and environmental sustainability. Agronomical solutions, such as deficit irrigation (water supply below full crop evapotranspiration) have emerged as a tool for more efficient water use in irrigated viticulture and with likely positive effects on berry quality. Improving our understanding on the physiological and molecular basis of grapevine responses to water stress is an important task for research on irrigated viticulture. Better knowledge of the different genotypic responses (e.g., leaf gas exchange) to water stress can help to optimize crop/soil management and improve yield as well as berry quality traits under unfavourable climate conditions. Mild water deficits have direct and/or indirect (via the light environment in the cluster zone) effects on berry growth and composition. Another important challenge is to determine how soil water deficit regulate genes and proteins of the various metabolic pathways influencing berry composition and consequently wine quality.
- Drought stress effects on C metabolism of sun and shade leaves of Vitis vinifera growing under field conditionsPublication . Maroco, J.P.; Rodrigues, A.; Breia, E.; Rodrigues, M.L.; Lopes, C.M.; Chaves, M.M.
- Effects of partial root drying on the physiology and production of grapevinesPublication . Souza, C.; Santos, T.; Rodrigues, A.S.; Lopes, C.M.; Rodrigues, M.L.; Pereira, J.S.
- Effects of partial root drying on the physiology and production of grapevinesPublication . Souza, C.R.; Maroco, J.P.; Chaves, M.M.; Santos, T.; Rodrigues, M.L.; Pereira, J.S.; Lopes, C.M.
- Effects of partial root-zone drying irrigation on grapevine microclimate and fruit compositionPublication . Santos, T.; Lopes, C.M.; Rodrigues, M.L.; Souza, C.; Ricardo-da-Silva, J.; Maroco, J.; Pereira, J.S.; Chaves, M.M.
- Effects of soil management and deficit irrigation strategies on physiological and agronomical responses of Aragonez field-grown grapevinesPublication . Santos, T.P.; Lopes, C.M.; Rodrigues, M.L.; Costa, M.; Ortuno, M.F.; Chaves, M.M.The use of irrigation in Mediterranean viticulture is now a common practice in intensive grapevine production to improve quality of production. The negative effects of water deficits on grape berry development are well known but the underlying mechanisms remain not fully understood. To avoid the unfavourable impacts of mechanization on the soil structure and biology some farmers are using cover crops on their vineyards. Within this frame we have compared the traditional soil tillage with a high level of mechanization with other system where we maintained a permanent soil cover between the rows. In both soil systems we tested three different irrigation treatments, deficit irrigation (DI - 40% of evapotranspiration (ETc)); regulated deficit irrigation (RDI); partial root drying (PRD) while in the soil cover treatment we also studied the full irrigation (FI) and the non irrigation (NI) treatments. Compared to soil tillage the resident vegetation reduced soil water content during late Spring, before irrigation started, inducing a significant reduction on vine vegetative growth berry weight and yield. Among irrigation strategies only RDI treatment showed a significant reduction in the lateral leaf area development, berry weight and yield when compared to PRD and DI treatments which presented similar values. No significant differences were observed in berry composition either for the two floor management practices or for the three irrigation strategies
- Eficiência do uso da água e rega deficitáriaPublication . Chaves, M.M.; Santos, T.P.; Ortuno, M.F.; Rodrigues, M.L.; Lopes, C.M.; Maroco, J.P.; Pereira, J.S.O conhecimento dos factores que regulam o balanço entre assimilação de carbono e perda de água por transpiração, bem como os que regulam a partição dos assimilados entre estruturas vegetativas e reprodutivas relativamente à disponibilidade de água, são essenciais para identificar tecnologias que permitam ajustar a rega às necessidades da planta. Grandes fluxos de água não são essenciais para o funcionamento adequado das plantas e pode-se poupar água manipulando o funcionamento dos estomas, através da exploração da sinalização química de longa-distância, entre a raiz e a parte aérea. Nos últimos anos desenvolveram-se diferentes modalidades de rega, que permitem aumentar a eficiência do uso da água, sem perdas significativas de rendimento e com eventuais ganhos de qualidade da produção. Com base na resposta fisiológica das culturas ao deficit hídrico, são hoje utilizados vários tipos de rega deficitária. No presente trabalho descreve-se um caso-de-estudo com a vinha em que se comparam os efeitos de diferentes tipos de rega na produção (quantidade e qualidade), bem como sobre os processos fisiológicos que explicam as diferenças encontradas. Os resultados dos nossos estudos sugerem que as videiras do tratamento PRD (rega parcial das raízes com 50% da evapotranspiração da cultura, ETc, fornecida alternadamente a cada lado do sistema radicular) mostram uma diminuição do vigor relativamente às FI (rega com 100 % da ETc) e DI (rega com 50% da ETc, 25% fornecido a cada metade do sistema radicular). O vigor das videiras PRD aproxima-se do observado em videiras não regadas (NI), o que se reflecte num aumento da exposição dos cachos nas videiras PRD e NI relativamente às DI e FI. Relativamente aos principais processos fisiológicos que determinam a eficiência do uso da água, observou-se nas videiras PRD e DI uma redução na condutância estomática e no fluxo da seiva relativamente às FI, mas as diferenças entre PRD e DI são subtis, variáveis com a data, com a variedade e mais visíveis em condições controladas do que no campo. A redução observada na condutância estomática no PRD, apesar de pouco marcada, explicará parcialmente a manutenção do estado hídrico mais próximo das FI do que das DI. Adicionalmente a alteração da arquitectura e da dimensão do sistema radicular nas videiras PRD, em que se observou um aumento das raízes em profundidade relativamente aos outros tratamentos, pode explicar uma maior eficiência na captação da água pela planta. Relativamente ao rendimento e qualidade do fruto, observou-se uma maior concentração de antocianinas nas películas dos bagos e de fenóis totais nas videiras PRD e NI do que nas DI e FI, confirmando o impacto da rega na intercepção da luz, em particular na zona do cacho. O tipo de rega não alterou significativamente a acumulação de açúcares nos bagos e o pH do mosto
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