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1.
We studied the short-term (i.e., a few days) effect of a sudden increase in CO2 uptake by shoots on nutrient (NO3-, P ion, K+, Ca2+ and Mg2+) uptake by roots during vegetative growth of young walnut (Juglans nigra x J. major L.) trees. The increase in CO2 uptake was induced by a sudden increase in atmospheric CO2 concentration ([CO2]). Twelve 2-year-old trees were transplanted and grown in perlite-filled pots in a greenhouse. Rates of CO2 uptake and water loss by individual trees were determined by a branch bag method from 3 days before until 6 days after [CO2] was increased. Nutrient uptake rates were measured concurrently by a hydroponic recirculating nutrient solution system that provided non-limiting supplies of water and nutrients. Six control trees were kept in ambient [CO2] (360 ppm), and [CO2] was increased to 550 ppm for one set of three trees and to 800 ppm for another set of three trees. Before imposing the elevated [CO2] treatments, all trees exhibited similar daily water loss, CO2 uptake and nutrient uptake rates when expressed per unit leaf area to account for the tree size effect. Daily water loss rates were only slightly affected by elevated [CO2]. Carbon dioxide uptake rates greatly increased with increasing atmospheric [CO2], and nutrient uptake rates were proportional to CO2 uptake rates during the study period, except for P ion. Our results show that, despite the important carbon and nitrogen storage capacities previously observed in young walnut trees, nutrient uptake by roots is strongly coupled to carbon uptake by shoots over periods of a few days. 相似文献
2.
We investigated the effect of small-scale overstory gaps on the ecophysiology and growth of Quercus ithaburensis saplings. The study aim was to characterize how changes in daily exposure to direct beam radiation affect photosynthetic performance in the short term and growth and biomass partitioning in the long term. Using individual net-houses, the following treatments were applied: (a) Unshaded (daily irradiance = 100 %), (b) shading net with no gap (Shade-daily irradiance = 6 %), (c) shading net with 1 h gap allowing direct beam radiation (11:00 am–12:00 pm, Shade+1-irradiance = 20 %), (d) shading net with 3 h gap (11:00 am–2:00 pm, Shade+3-irradiance = 44 %). The experiment was performed in an irrigated field. We measured growth, biomass allocation, leaf traits, daily courses of leaf gas exchange and water potential. Oak dry-weight increased while height to dry-weight ratio and specific leaf area decreased with increasing daily exposure to direct beam radiation. Leaf chlorophyll content was less affected. Higher net carbon assimilation rates (A), stomatal conductance (gs) and A/gs were associated with higher instantaneous photosynthetic photon flux density (PPFD) throughout the entire experimental PPFD range. However, during gap-hours, while exposed to saturating radiation levels of similar level (ca. 1,800 µmol photon m?2 s?1), A in the Shade+1 oaks was about half that of the Shade+3 oaks and nearly one-third that of the Unshaded oaks. Patterns of gs, intercellular CO2 (Ci) and quantum efficiency of photosystem II pointed towards the possibility of a metabolic limitation. In conclusion, oaks benefited significantly from small scale overstory gaps though their capacity to utilize transient saturating radiation levels decreased with decreasing gap duration. 相似文献
3.
Antigenotoxic effect of grape seed procyanidin extract in Fao cells submitted to oxidative stress 总被引：4，自引：0，他引：4
Llópiz N Puiggròs F Céspedes E Arola L Ardévol A Bladé C Salvadó MJ 《Journal of agricultural and food chemistry》2004,52(5):1083-1087
The protective effects of grape seed procyanidin extract on the repair of H(2)O(2)-induced DNA lesions were tested using Fao cells. Cells were exposed to 600 microM H(2)O(2) for 3 or 21 h. A procyanidin extract from grape seed (PE) was incubated or preincubated (1 h) during the exposure to H(2)O(2). The ability of procyanidins to protect against the genotoxicity of H(2)O(2) was compared with those of the monomeric flavanols (+)-catechin and (-)-epicatechin and the flavonol quercetin. After treatment, DNA damage was monitored using alkaline single-cell gel electrophoresis (the comet assay) (Aherne, S. A.; O'Brien, N. M. Nutr. Cancer 1999, 34, 160-166). At the end of the experiment, PE significantly decreased the damage caused by H(2)O(2). The results also showed that quercetin was the most effective of the flavonoids tested, which is consistent with its powerful antioxidant character. The results indicate that procyanidins are more effective than the corresponding individual monomers, catechin and epicatechin, at preventing DNA lesions in hepatocytes and that this protection is higher after preincubation than after co-incubation. 相似文献
4.
Yagil Osem Ela Zangy Eitan Bney-Moshe Yosi Moshe Naftali Karni Yehuda Nisan 《Forest Ecology and Management》2009
The aim was to study the potential for using natural regeneration as a basis for transformation of simply structured conifer plantations into mixed Mediterranean forests. We studied the variation along a rainfall gradient, in the natural regeneration of tree species in the understory of planted 40- to 50-year-old Aleppo pine (Pinus halepensis) forests. The study was conducted within the Mediterranean zone of Israel, which extends from the semiarid northern Negev desert (rainfall ca. 300 mm yr−1) in the south to the humid Upper Galilee in the north (ca 900 mm yr−1). Cover and height, density, and species composition of regenerating trees were measured on south- and north-facing slopes in forest sites of comparable silvicultural history (site preparation methodology, planting density and thinning regime) distributed along the rainfall gradient. Altogether, 12 species of regenerating native broadleaved trees were found in the understory of the various forest sites. Surface cover, density and species richness increased linearly along the entire rainfall gradient, on both north- and south-facing slopes, ranging from zero in the driest forest sites up to 85% cover, 7980 trees ha−1 and 4.5 species per 200 m2, respectively, in the most humid ones. Species composition of regenerating trees was also related to rainfall amount, through changes in the relative importance of species along the rainfall gradient. The effect of topographic aspect on tree regeneration was inconsistent, i.e., the interaction Rainfall × Aspect was significant. Nevertheless, the general trend showed better regeneration on north-facing slopes. Most of the regenerating trees in the understory were small, i.e., less than 100 cm in height, with no clear effect of rainfall amount and topographic aspect on the relative abundance of height classes. Regeneration by Aleppo pine was highly variable among and within the different forest sites and ranged from 0 to 1565 trees ha−1, with no clear relationships with rainfall amount and topographic aspect. In light of our results we propose that the future structure of forests should vary with respect to annual rainfall amount within possible silvicultural scenarios. 相似文献
5.
The aim of this study is to compare the performance between Water User Associations (WUAs) and cooperatives in the Gediz River
Basin in Turkey by applying a set of external comparative performance indicators. The indicators allow for the comparison
of irrigation performance between the two organisations. Benchmarking indicators were used to best evaluate the differences,
achievements and failures. The indicators included fee collection rate, cost recovery, general meeting attendance, irrigation
and personnel intensity. The data was collected over a 7-year period from 1997 to 2003, inclusive. The article clearly shows
that, with respect to the selected indicators, both WUAs and cooperatives performed well. Personnel intensity is the one area
that both organisations could improve upon. Overall, WUAs function better than cooperatives. The findings and conclusions
drawn from this research will be beneficial to managers responsible for policy-making decisions for the future attempts on
irrigation management. 相似文献
6.
Typhoon Yolanda brought major devastation to the local communities and infrastructure and also reshaped social structures and networks in the Philippines. During the immediate recovery process, bridging, bonding and linking social capital have had differential impacts and outcomes on how communities cope with the aftermath of the disaster. This article investigates the interplay between the various types of social capital and their contributions to immediate coping strategies of Typhoon Yolanda communities. This article also evaluates the complexity of defining social capital in a disaster context. In particular, it unpacks the blurring of the bridging and linking social capital at the immediate stage of rehabilitation in a post‐disaster context and its impacts on the social fabric of the communities. We deduce from this case study the social capital strategies necessary for a speedy recovery process both economically and socially for disaster‐affected communities. 相似文献
7.
Eric JUSTES Laurent BEDOUSSAC Christos DORDAS Ela FRAK Gaetan LOUARN Simon BOUDSOCQ Etienne-Pascal JOURNET Anastasios LITHOURGIDIS Chrysanthi PANKOU Chaochun ZHANG Georg CARLSSON Erik Steen JENSEN Christine WATSON Long LI 《农业科学与工程前沿(英文版)》2021,8(3):387
8.
In pot experiments, powdery mildew of cucumber, caused bySphaerotheca fuliginea, was reduced by 64-82% by the film-forming polymer Vapor Gard and by up to 55% by Wilt Pruf. In experiments in polyethylene-covered greenhouses, no harmful effect to the crop was caused by these materials. In one experiment significant disease reductions of 19-67% and 60-96% were obtained by 3% Safe Pack and by the fungicide fenarimol (Rubigan), respectively. The combined treatment of Safe Pack with the fungicide was significantly more effective than either treatment alone, 72-78 days after planting. In another experiment, disease that appeared late in the season was reduced by up to 80, 100, 30 and 96% by Vapor Gard, Folicote, Wilt Pruf and fenarimol, respectively, and was statistically different from the nontreated control in some of the treatments and dates. Most tested substances inhibited germination ofS. fuliginea conidia and growth of its hyphae on leaves of cucumber. 相似文献
9.