Cold acclimation of winter and spring peas: carbon partitioning as affected by light intensity   总被引：4，自引：0，他引：4  

Virginie Bourion  Isabelle Lejeune-Hnaut  Nathalie Munier-Jolain  Christophe Salon 《European Journal of Agronomy》2003,19(4):535-548

Like most plants, pea (Pisum sativum L.) becomes tolerant to frost if it is first exposed to low non-freezing temperatures, a process known as cold acclimation. Cold acclimation is a complex process involving many physiological and metabolic changes. Two spring dry peas, two winter dry peas and one winter forage line were exposed to cold temperature in a controlled environment in two experiments, one using low light intensity and the other regular light intensity. Plants were harvested throughout the experiment and dry matter accumulation, water content, soluble and insoluble sugar concentrations were determined from shoot and root samples. Cold acclimation did not occur when temperatures were low if light intensity was low, even in winter peas. In contrast, with regular light intensity, the winter peas acquired more freezing tolerance than spring peas and a close relationship was found between the soluble sugar concentration of leaves just before the frost and the degree of freezing tolerance obtained by the different genotypes. Relationships between freezing tolerance and carbon partitioning between shoot and roots are discussed.  相似文献   

Variability of the polyphenolic composition of cider apple (Malus domestica) fruits and juices     

Guyot S  Marnet N  Sanoner P  Drilleau JF 《Journal of agricultural and food chemistry》2003,51(21):6240-6247

Five French cider apple varieties were compared on the basis of their detailed polyphenol profile in the cortex and in the juices. Among the factors studied, variety was the most important variability factor in fruits, whereas polyphenol profiles showed an overall stability from one year to another, and a limited decrease of polyphenol concentration was observed during the starch regression period of fruit maturation. In juices, procyanidins remained the preponderant polyphenol class with concentrations up to 2.4 g/L even in centrifuged juices. Compared to the fruits, the average degree of polymerization of procyanidins was significantly reduced in the juice. Centrifugation of the crude juice had only minor effects on the polyphenol composition. For one variety, highly polymerized procyanidins with average degrees of polymerization of 25 were shown to be soluble in the centrifuged juice at a concentration of close to 1.2 g/L. Oxygenation of the juices during processing resulted in a significant decrease of all classes of native polyphenols. Catechins and procyanidins were particularly affected by oxidation, whereas caffeoylquinic acid was partly preserved. The transfer of polyphenols after pressing was maximal for dihydrochalcones and minimal for procyanidins with extraction yield values close to 80 and 30%, respectively.  相似文献   

Composition rather than viscosity modifies the aroma compound retention of flavored stirred yogurt     

Kora EP  Souchon I  Latrille E  Martin N  Marin M 《Journal of agricultural and food chemistry》2004,52(10):3048-3056

The influence of thickening agents (modified starch/pectin mixture 0 and 7 g/L) and mechanical treatment (low, medium, and high) on the retention of esters (pentyl acetate and ethyl pentanoate), aldehydes (hexanal and (E)-2-hexenal), and a lactone (gamma-octalactone) in low-fat flavored stirred yogurts were investigated under equilibrium conditions. In the range studied, the thickening agent and mechanical treatment had little influence on aroma compound retention compared to the decreasing effect of increasing dairy protein concentration on aldehyde retention and the "salting out" effect of carbohydrates on esters. Moreover, experiments in dynamic mode (study of the release of hexanal when yogurts were heated) showed, in the conditions studied, that heat and mass transfer coefficients were not influenced by any of the studied factors (thickening agents and mechanical treatment). These results under static and dynamic conditions are not related to the significant decreasing effect of thickening agents on apple sensory scores associated with hexanal, observed in a previous sensory study. Thus, this sensory effect of thickening agents may be due to sensory interactions between perceptions rather than physicochemical interactions.  相似文献   

Oxidative stability of bovine serum albumin- and sodium caseinate-stabilized emulsions depends on metal availability     

Villiere A  Viau M  Bronnec I  Moreau N  Genot C 《Journal of agricultural and food chemistry》2005,53(5):1514-1520

Proteins often stabilize food emulsions and are also able to promote or delay lipid oxidation in complex systems. The purpose of this work was to investigate the relationship between metal ion availability and oxidative stability of oil-in-water emulsions stabilized by bovine serum albumin (BSA) or sodium caseinate (NaCas). Emulsions with similar and stable droplet size distributions were prepared with stripped sunflower oil (30 vol %) and protein solutions (20 g L(-)(1); pH = 6.5). In the absence of the water-soluble metal chelator EDTA, oxygen uptake, conjugated dienes, and volatile compounds developed faster in NaCas-stabilized emulsions than in those prepared with BSA. This effect is attributed to the chelating properties of NaCas and to electrostatic interactions that attract some metal ions at the interface where they could initiate lipid oxidation. When EDTA (100 muM) was present, oxidation was delayed to a greater extent in emulsions made with NaCas than in BSA stabilized emulsions. These conditions probably enabled NaCas to exert free-radical-scavenging activity.  相似文献   

Origin of French virgin olive oil registered designation of origins predicted by chemometric analysis of synchronous excitation-emission fluorescence spectra     

Dupuy N  Le Dréau Y  Ollivier D  Artaud J  Pinatel C  Kister J 《Journal of agricultural and food chemistry》2005,53(24):9361-9368

The authentication of virgin olive oil samples requires usually the use of sophisticated and very expensive analytical techniques, so there is a need for fast and inexpensive analytical techniques for use in a quality control methodology. Virgin olive oils present an intense fluorescence spectra. Synchronous excitation-emission fluorescence spectroscopy (SEEFS) was assessed for origin determination of virgin olive oil samples from five French registered designation of origins (RDOs) (Nyons, Vallée des Baux, Aix-en-Provence, Haute-Provence, and Nice). The spectra present bands between 600 and 700 nm in emission due to chlorophylls a and b and pheophytins a and b. The bands between 275 and 400 nm in emission were attributed to alpha-, beta-, and gamma-tocopherols and to phenolic compounds, which characterize the virgin olive oils compared to other edible oils. The chemometric treatment (PLS1) of synchronous excitation-emission fluorescence spectra allows one to determine the origin of the oils from five French RDOs (Baux, Aix, Haute-Provence, Nice, and Nyons). Results were quite satisfactory, despite the similarity between two denominations of origin (Baux and Aix) that are composed by some common cultivars (Aglandau and Salonenque). The interpretation of the regression coefficients shows that RDOs are correlated to chlorophylls, pheophytins, tocopherols, and phenols compounds, which are different for each origin. SEEFS is part of a global analytic methodology that associates spectroscopic and chromatographic techniques. This approach can be used for traceability and vindicates the RDOs.  相似文献   

Direct activation of Bax by p53 mediates mitochondrial membrane permeabilization and apoptosis     

Chipuk JE  Kuwana T  Bouchier-Hayes L  Droin NM  Newmeyer DD  Schuler M  Green DR 《Science (New York, N.Y.)》2004,303(5660):1010-1014

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Platforms for collective action in multiple-use common-pool resources     

Nathalie A. Steins  Victoria M. Edwards 《Agriculture and Human Values》1999,16(3):241-255

Collective action processes in complex, multiple-use common-pool resources (CPRs) have only recently become a focus of study. When CPRs evolve into more complex systems, resource use by separate user groups becomes increasingly interdependent. This implies, amongst others, that the institutional framework governing resource use has to be re-negotiated to avoid adverse impacts associated with the increased access of any new stakeholders, such as overexploitation, alienation of traditional users, and inter-user conflicts. The establishment of platforms for resource use negotiation is a way of dealing with complex natural resource management problems. Platforms arise when stakeholders perceive the same resource management problem, realize their interdependence in solving it, and come together to agree on action strategies for solving the problem (Röling, 1994). This article sets the scene for a discussion in this Special Issue about the potential of nested platforms for resource use negotiation in facilitating collective action in the management of complex, multiple-use CPRs. The article has five objectives. First, we define collective action in the context of this paper. Second, we discuss the importance of collective action in multiple-use CPRs. Third, we introduce the concept of platforms to coordinate collective action by multiple users. Fourth, we address some issues that emerge from evidence in the field regarding the role and potential of nested platforms for managing complex CPRs. Finally, we raise five discussion statements. These will form the basis for the collection of articles in this special issue.  相似文献   

Antigen bias in T cell cross-priming   总被引：1，自引：0，他引：1  

Wolkers MC  Brouwenstijn N  Bakker AH  Toebes M  Schumacher TN 《Science (New York, N.Y.)》2004,304(5675):1314-1317

Activated CD8+ T cells detect virally infected cells and tumor cells by recognition of major histocompatibility complex class I-bound peptides derived from degraded, endogenously produced proteins. In contrast, CD8+ T cell activation often occurs through interaction with specialized antigen-presenting cells displaying peptides acquired from an exogenous cellular source, a process termed cross-priming. Here, we observed a marked inefficiency in exogenous presentation of epitopes derived from signal sequences in mouse models. These data indicate that certain virus- and tumor-associated antigens may not be detected by CD8+ T cells because of impaired cross-priming. Such differences in the ability to cross-present antigens should form important considerations in vaccine design.  相似文献   

Geochemistry. Fuel for plate tectonics     

Bolfan-Casanova N 《Science (New York, N.Y.)》2007,315(5810):338-339

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Bacterial persistence as a phenotypic switch     

Balaban NQ  Merrin J  Chait R  Kowalik L  Leibler S 《Science (New York, N.Y.)》2004,305(5690):1622-1625

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