Browsing by Author "Lopes, Carlos Manuel Antunes"
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- Control of stomatal aperture and carbon uptake by deficit irrigation in two grapevine cultivarsPublication . Souza, Cláudia R. de; Maroco, João; Santos, Tiago P.; Rodrigues, M. Lucília; Lopes, Carlos Manuel Antunes; Pereira, João Santos; Chaves, Maria Manuelaodels for the Mediterranean region. In recent years, deficit irrigation, including partial root drying (PRD), has been proposed as an irrigation technique to improve water use efficiency and standardize grapevine yield and quality. The objective of this study was to evaluate the impact of deficit irrigation on photosynthetic responses of field grown grapevines of cv. Moscatel and Castela˜o. The treatments were: full irrigation (FI), corresponding to 100% ETc; non-irrigated, but rain fed (NI) and partial root zone drying (PRD) and deficit irrigation (DI), both corresponding to an irrigation of 50% ETc. While in the DI treatment water was applied to both sides of the root system, in the PRD treatment, water was supplied to only one side of the root system, alternating sides periodically. In both cultivars, PRD and DI vines showed intermediate pre-dawn leaf water potential (ψpd) values (around -0.4 MPa) while FI vines, showed ψpd around -0.2 MPa during the growing season. NI showed the lowest cpd, reaching -0.6 MPa in Moscatel and -0.8 MPa in Castelão, at the end of growing season. Water status of PRD vines remained closer to FI than DI, especially at midday. Photosynthetic rates and fluorescence parameters of the deficit irrigation treatments (PRD and DI) did not show significant differences from FI vines, for most of the season. In Moscatel, although PRD generally showed gs, relative stomatal limitation (RSL) and intrinsic water use efficiency (A/gs) values closer to NI than DI, most of the differences between PRD and DI were not statistically significant. Our results showed a stability of the photosynthetic machinery in grapevines under low-to-moderate water availabilities, as demonstrated by the maintenance of the activity of three Calvin Cycle enzymes and of the Vcmax values. However, a decline in Jmax was observed in NI vines, that can be a result either of a decrease in ATP production or, alternatively, of decreased mesophyll conductance to CO2 diffusion. In general terms, stomatal limitation of photosynthesis is likely to be dominant in non-irrigated plants. Deficit irrigation had no negative impact on CO2 assimilation, despite less water application than in full-irrigation. Differences among varieties may be related to differences in sensitivity of stomata, shoot growth and/or the interaction between rootstock and cultivar to soil water availability.
- Deficit irrigation in grapevine improves water-use efficiency while controlling vigour and production qualityPublication . Chaves, Maria Manuela; Santos, Tiago P.; Souza, Cláudia R. de; Ortuño, M. F.; Rodrigues, M. Lucília; Lopes, Carlos Manuel Antunes; Maroco, João; Pereira, João SantosGrapevine irrigation is becoming an important practice to guarantee wine quality or even plant survival in regions affected by seasonal drought. Nevertheless, irrigation has to be controlled to optimise source to sink balance and avoid excessive vigour. The results we present here in two grapevine varieties (Moscatel and Castela ˜o) during 3 years, indicate thatwe can decrease the amount ofwater applied by 50%(as in deficit irrigation, DI, and in partial root drying, PRD) in relation to full crop’s evapotranspiration (ETc) [full irrigated (FI) vines] with no negative effects on production and even get some gains of quality (in the case of PRD).We report that in non-irrigated and in several cases in PRD vines exhibit higher concentrations of berry skin anthocyanins and total phenols than those presented by DI and FI vines.We showed that these effects on quality weremediated by a reduction in vigour, leading to an increase on light interception in the cluster zone. Because plant water status during most of the dates along the season was not significantly different between PRD and DI, and when different, PRD even exhibited a higher leaf water potential than DI vines, we conclude that growth inhibition in PRD was not a result of a hydraulic control. The gain in crop water use in DI and PRD was accompanied by an increase of the δ13 C values in the berries in DI and PRD as compared to FI, suggesting that we can use this methodology to assess the integrated water-use efficiency over the growing season.
- Effects of partial root-zone drying irrigation on cluster microclimate and fruit composition of field-grown Castelão grapevinesPublication . Santos, Tiago P.; Lopes, Carlos Manuel Antunes; Rodrigues, M. Lucília; Souza, Cláudia R. de; Silva, Jorge R.; Maroco, João; Pereira, João Santos; Chaves, Maria ManuelaThe partial root-zone drying (PRD) irrigation technique has been proposed for viticulture as a possible way to save water without compromising yield. Half of the plant root system is slowly dehydrating whereas the other half is irrigated; after about two weeks the opposite side of vines is irrigated. A PRD irrigation system (50 % of the crop evapotranspiration - ETc) was installed in a vineyard (Vitis vinifera L. cv. Castelão) in Southern Portugal and compared with two other irrigation systems, deficit irrigation, DI (50 % ETc) and full irrigation, FI (100 % ETc), as well as with non-irrigated vines (NI). Water was applied twice a week, from fruit set (mid-June) until one week before harvest (September 3). While FI vines remained well watered during the ripening period, a severe water stress developed in NI plants. PRD and DI vines exhibited mild water deficits during the same period. A significant decrease in vegetative growth (shoot weight, pruning weight, leaf layer number and percentage of water shoots) was observed in NI and PRD vines when compared to DI and FI. In denser canopies (FI and DI) berry temperature was always lower than that of the more open ones (NI and PRD). The higher degree of cluster exposition in PRD and NI had a positive influence on berry composition due to temperature and incident radiation, leading to higher concentrations of anthocyanins and total phenols in the berry skin compared to DI and FI vines. Irrigation did not significantly affect berry sugar accumulation and pH in berries. Compared to FI, PRD and DI treatments water use efficiency (the amount of fruit produced per unit of water applied) was doubled since at the same yield the amount of water applied, was reduced by 50 %.
- Grape berry metabolism in field-grown grapevines exposed to different irrigation strategiesPublication . Souza, Cláudia R. de; Maroco, João; Santos, Tiago P.; Rodrigues, M. Lucília; Lopes, Carlos Manuel Antunes; Pereira, João Santos; Chaves, Maria ManuelaThe response of grape berry metabolism to vine water status was investigated in field grown grapevines (Vitis vinifera cv. Castelão) in southern Portugal. Water was supplied as: full irrigation (FI), to minimum water deficit corresponding to 100 % of crop evapotranspiration (Etc), partial rootzone drying (PRD) and deficit irrigation (DI), both corresponding to an irrigation amount of 50 % Etc, and a rainfed, i.e. no irrigation treatment (NI). In PRD, water was supplied to one side of the root system during each irrigation period, alternating sides every 15 d approximately. During the growing period, PRD and DI vines showed intermediate pre-dawn leaf water potential (Ψpd) values (around -0.4 MPa) by the end of the growing season, FI vines -0.2 MPa and NI -0.8 MPa. Berry weight as well as the content of glucose and fructose per berry increased in irrigated vines (PRD, DI, and FI) compared to NI vines. Although both malic and tartaric acid declined in non-irrigated vines, there was no significant difference between treatments at harvest. The activities of invertase, malate dehydrogenase and malic enzyme were not affected by irrigation throughout the ripening process. The contribution of other factors involved in the reduction of sugars and organic acids in berries of non-irrigated vines are discussed. These results show that deficit irrigation, like PRD and DI, do not have any negative impact on growth and quality of grape berries compared to fully irrigated vines, but may result in improved berry quality compared to rainfed vines.
- Impact of deficit irrigation on water use efficiency and carbon isotope composition (δ13C) of field-grown grapevines under Mediterranean climatePublication . Souza, Cláudia R. de; Maroco, João; Santos, Tiago P.; Rodrigues, M. Lucília; Lopes, Carlos Manuel Antunes; Pereira, João Santos; Chaves, Maria ManuelaThe objective of this study was to evaluate the effect of deficit irrigation on intrinsic water use efficiency (A/gs) and carbon isotope composition (δ 13C) of two grapevine cultivars (Moscatel and Castelão), growing in a commercial vineyard in SW Portugal. The study was done in two consecutive years (2001 and 2002). The treatments were full irrigation (FI), corresponding to 100% of crop evapotranspiration (ETc), rain-fed (no irrigation, NI), and two types of deficit irrigation (50% ETc): (i) by supplying the water either to one side of the root system or to the other, which is partial rootzone drying (PRD), or (ii) dividing the same amount of water by the two sides of the root system, the normal deficit irrigation (DI). The water supplied to the PRD treatment alternated sides approximately every 15 d. The values of predawn leaf water potential (ψpd) and the cumulative integral of ψpd (Sψ) during the season were lower in 2001 than in the 2002 growing season. Whereas differences in Wpd and SW between PRD and DI were not significantly different in 2001, in 2002 (a dryer year) both cultivars showed lower values of SW in the PRD treatment as compared with the DI treatment. This suggests that partial rootzone drying may have a positive effect on water use under dryer conditions, either as a result of better stomatal control and/or reduced vigour. The effects of the water treatments on δ13C were more pronounced in whole grape berries and pulp than in leaves. The δ13C of pulp showed the best correlation with intrinsic water use efficiency (A/gs) as well as with Sψ. In spite of the better water status observed in PRD compared with DI in the two cultivars in 2002, no statistical differences between the two treatments were observed in A/gs and δ13C. On the other hand, they showed a higher δ13C compared with FI. In conclusion, it is apparent that the response to deficit irrigation varies with the environmental conditions of the particular year, the driest conditions exacerbating the differences among treatments. The highest values of d13C found in the pulp of NI vines in Castela˜o compared with Moscatel suggest different sensitivities to water deficits in the two cultivars, as was empirically observed.
- Limitations to leaf photosynthesis in field-grown grapevine under drought - metabolic and modelling approachesPublication . Maroco, João; Rodrigues, M. Lucília; Lopes, Carlos Manuel Antunes; Chaves, Maria ManuelaThe effects of a slowly-imposed drought stress on gas-exchange, chlorophyll a fluorescence, biochemical and physiological parameters of Vitis vinifera L. leaves (cv. Aragonez, syn. Tempranillo) growing in a commercial vineyard (South Portugal) were evaluated. Relative to well-watered plants (predawn water potential, ΨPD = –0.13 ± 0.01 MPa), drought-stressed plants (ΨPD = –0.97 ± 0.01 MPa) had lower photosynthetic rates (ca 70%), stomatal conductance, and PSII activity (associated with a higher reduction of the quinone A pool and lower efficiency of PSII open centres). Stomatal limitation to photosynthesis was increased in drought-stressed plants relative to well-watered plants by ca 44%. Modelled responses of net photosynthesis to internal CO2 indicated that drought-stressed plants had significant reductions in maximum Rubisco carboxylation activity (ca 32%), ribulose-1,5-bisphosphate regeneration (ca 27%), and triose phosphate (triose-P) utilization rates (ca 37%) relative to well-watered plants. There was good agreement between the effects of drought on modelled biochemical parameters, and in vitro activities of key enzymes of carbon metabolism, namely Rubisco, glyceraldehyde-3-phosphate dehydrogenase, ribulose-5-phosphate kinase and fructose-1,6-bisphosphate phosphatase. Quantum yields measured under both ambient (35 Pa) and saturating CO2 (100 Pa) for drought-stressed plants were decreased relative to well-watered plants, as well as maximum photosynthetic rates measured at light and CO2 saturating conditions (three times ambient CO2 levels). Although stomatal closure was a strong limitation to CO2 assimilation under drought, comparable reductions in electron transport, CO2 carboxylation, and utilization of triose-P capacities were also adaptations of the photosynthetic machinery to dehydration that slowly developed under field conditions. Results presented in this study confirm that modelling photosynthetic responses based on gas-exchange data can be successfully used to predict metabolic limitations to photosynthesis.
- Partial rootzone drying: effects on growth and fruit quality of field-grown grapevines (Vitis vinifera)Publication . Santos, Tiago P.; Lopes, Carlos Manuel Antunes; Rodrigues, M. Lucília; Souza, Cláudia R. de; Maroco, João; Pereira, João Santos; Silva, Jorge R.; Chaves, Maria ManuelaA study to assess the effects of the Partial Rootzone Drying (PRD) irrigation strategy in comparison to other irrigation systems was carried out in southern Portugal in two field-grown grapevines varieties, Moscatel and Castelão. We addressed the question of whether by regulating growth and plant water use, the PRD system would enable an equilibrated vegetative development, leading to a favourable capture of solar radiation for photoassimilate production and, at the same time to provide an optimum environment for fruit maturation. Three irrigation schemes were applied in addition to the non-irrigated (NI) vines: partial root drying (PRD), 50% of crop evapotranspiration (ETc), supplied to only one side of the root system while the other one was allowed to dry, alternating sides every 15 days; deficit irrigated (DI), 50% ETc supplied, half to each side of the root system and full irrigated (FI, 100% ETc). During the whole season FI plants of both varieties exhibited a high leaf predawn water potential (ψpd , ca –0.2 MPa) while a progressive decline was observed in NI plants, reaching ψpd values near –0.7 MPa at the end of August. PRD and DI presented intermediate values. PRD vines exhibited a stronger control over vegetative growth as compared with DI and FI plants. This was expressed by lower values of total leaf area at harvest, leaf layer number, canopy wideness and water shoots number, allowing a higher light interception at the cluster zone that induced an improvement in some berry quality characteristics. Watering had no significant effects on sugar accumulation in the berries but led to a favourable increase in the must titratable acidity, mainly in Castelão. Whereas in DI and FI treatments berry skin anthocyanins and phenols content were always lower than in NI, in PRD there was either no reduction or the reduction was much lower than in the other irrigation treatments. Water use efficiency (WUE) was increased by about 80% in PRD and DI when compared with FI, as a result of almost similar yields in the three treatments. Yield gains of irrigated plants in relation to NI were modest, explained by the rainy spring in both years.
- Partial rootzone drying: Regulation of stomatal aperture and carbon assimilation in field-grown grapevines (Vitis vinifera cv. Moscatel)Publication . Souza, Cláudia R. de; Maroco, João; Santos, Tiago P.; Rodrigues, M. Lucília; Lopes, Carlos Manuel Antunes; Pereira, João Santos; Chaves, Maria ManuelaThe effects of 'partial rootzone drying' (PRD) irrigation compared with other irrigation systems, namely non-irrigated (NI), full irrigation (FI) and deficit irrigation (DI), on stomatal conductance and carbon assimilation were evaluated in field-grown grapevines (Vitis vinifera L. cv. Moscatel). At the end of the growing season, pre-dawn leaf water potential was highest in FI (–0.18 ± 0.01 MPa; mean ± s.e.), intermediate in PRD (–0.30 ± 0.01 MPa) and DI (–0.36 ± 0.02 MPa), and lowest in NI vines (–0.64 ± 0.03 MPa). Stomatal conductance measured under controlled conditions of light and temperature was reduced in NI (ca 60%) and PRD (ca 30%) vines compared with DI and FI vines. Under ambient conditions, NI vines had lower rates of stomatal conductance (ca 26%), net CO2 assimilation (ca 28%) and light-adapted PSII quantum yields (ca 47%) than PRD, DI and FI vines. No significant differences were found among the three irrigated treatments. Both maximum electron transport rate (Jmax; ca 30%) and triose-phosphate utilization rates (TPU; ca 20%) were significantly lower in NI and PRD vines than in DI and FI vines. Carbon isotope composition (δ13C) of grape berries was highest in NI vines (–24.3‰), followed by PRD (–25.4‰) and DI (–25.8‰) and lowest in FI (–26.4‰) vines, suggesting a long-term increase in the efficiency of leaf gas exchange in NI compared with PRD, DI and FI vines. Sap-flow data and estimates of relative stomatal limitation are in accordance with the observed stomatal closure in PRD vines. In this study, we show that PRD irrigation was able to maintain a vine water status closed to FI, but with double water use efficiency, which was due to a reduction of stomatal conductance with no significant decrease in carbon assimilation.