Explore the vast range of titles available.

Low temperature driven carbon shortage is often assumed to explain slow growth and treeline formation at high elevations. To test this hypothesis, we analysed mobile carbon pools in Pinus cembra across the treeline ecotone in the Swiss Alps. Concentrations of non-structural carbohydrates (NSC) in needles, branches, stems and roots, as well as lipids (acylglycerols) in all woody tissues were measured throughout the growing season. Starch was the most prominent non-structural carbon compound in needles, whereas lipids represented 50-75% of the mobile carbon compounds in wood. The relative seasonal variation of the lipid fraction was very small, but due to the high absolute amount of lipids, the annual variability of carbon in lipids exceeded that of NSC in woody tissues. Mobile carbon compounds were highly abundant throughout the year and were never significantly depleted. Across a 110 m altitudinal transect from timberline to the uppermost site of tree existence, NSC and lipid concentrations generally increased. This trend became even more pronounced when the increasing structural density of tissues at higher elevations was accounted for. An estimation of the whole tree mobile carbon concentration (fraction of mobile carbon compounds within the whole tree biomass) also revealed an increasing trend of NSC and lipid pools with elevation. We therefore conclude that carbon limitation is unlikely to be responsible for reduced tree growth at the alpine treeline studied. Increased concentrations of NSC and lipids at the upper tree limit rather suggest that sink activity is limited. Hence, treeline formation is most likely the result of a direct thermal restriction of tissue formation (investment in structures) under otherwise sufficient carbon assimilation during the growing season.

Introduction. Consumers and processors value tomatoes with high fruit sugar content; however, most breeding and cultural practices negatively impact this trait. Wild tomato species can accumulate two- to three-fold more fruit sugar than cultivars and are proving to be valuable both as a source of high-sugar loci to broaden the genetic base of currently produced cultivars, and as research material to understand this trait. Synthesis. While cutting-edge genomic approaches have taught us much about fruit phenotypes, it is still important to assess fruit enzyme activities and metabolic fluxes in lines with contrasting fruit sugar accumulation. These metabolic functions are closest to the ripe fruit sugar trait. In this review, we focus our attention on the biochemical pathways, especially starch biosynthesis, that may influence tomato fruit sugars. We try where possible to put this information into a physiological context because together they influence yield. We compare and contrast sugar metabolism in cultivars and wild tomato species and identify factors that may influence differences in their fruit size. Conclusion. Although difficult, we show that it is possible to develop fruit with high horticultural yield and use the breeding line ‘Solara’ as an example. In addition, we suggest avenues of further investigation to understand the regulation and control of fruit carbohydrate content. Introduction. Les consommateurs et les industriels apprécient les tomates avec un fort taux en sucres, mais la plupart des pratiques culturales et d’amélioration ont un impact négatif sur ce caractère. Les espèces de tomate sauvage peuvent accumuler 2 ou 3 fois plus de sucres dans le fruit que des cultivars et elles s’avèrent précieuses à la fois comme une source de loci à haute teneur en sucres pour élargir la base génétique des cultivars actuellement produits, et comme matériel de recherche pour comprendre ce caractère. Synthèse. Alors que les approches génomiques de pointe nous ont appris beaucoup sur le phénotype des fruits, il reste important d’évaluer l’activité des enzymes de fruits et les flux métaboliques dans des lignées présentant des situations contrastées d’accumulation de sucres dans les fruits. Ces fonctions métaboliques sont les plus proches du caractère de teneur en sucres dans le fruit mûr. Dans cette synthèse, nous nous sommes focalisés sur les voies biochimiques, en particulier sur la biosynthèse de l’amidon qui peut influencer les sucres dans le fruit des tomates. Nous essayons autant que possible de mettre cette information dans un contexte physiologique car, ensemble, ils influencent le rendement. Nous comparons et mettons en contraste le métabolisme des sucres dans les cultivars et les espèces sauvages de tomate et nous identifions les facteurs qui peuvent influencer des différences de taille des fruits. Conclusion. Bien que cela soit difficile, nous montrons qu’il est possible de produire des fruits présentant un rendement horticole élevé et nous utilisons la lignée sélectionnée “ Solara ” comme exemple. En outre, nous suggérons des pistes de recherches supplémentaires pour comprendre la régulation et le contrôle du contenu en glucides des fruits. Introducción. Los consumidores e industriales aprecian los tomates con un fuerte índice de azúcares, pero la mayoría de las prácticas relativas al cultivo y de mejora tienen un impacto negativo sobre este rasgo característico. Las especies de tomate salvaje pueden acumular 2 ó 3 veces más azúcares en el fruto que los cultivares, y resultan ser apreciadas como fuente de loci de alto contenido en azúcares para aumentar la base genética de los cultivares actualmente producidos y como material de investigación para comprender dicho rasgo característico. Síntesis. A pesar de que los acercamientos genómicos punteros nos hayan enseñado mucho sobre el fenotipo de los frutos, sigue siendo importante evaluar la actividad de las encimas de los frutos, así como los flujos metabólicos en líneas que presenten situaciones contrastadas de acumulación de azúcares en los frutos. Dichas funciones metabólicas son las que más se acercan al rasgo característico del contenido de azúcares en el fruto maduro. En esta síntesis, nos centramos en las vías bioquímicas, particularmente en la biosíntesis del almidón, que puede influenciar los azúcares en el fruto del tomate. Intentamos, en la medida de lo posible, situar esta información en un contexto fisiológico, ya que, conjuntamente, influencian el rendimiento. Comparamos y contrastamos el metabolismo de los azúcares en los cultivares y en las especies salvajes de tomate, e identificamos los factores que pueden influenciar las diferencias en el tamaño de los frutos. Conclusión. A pesar de la dificultad, ilustramos la posibilidad de producir frutos que presenten un elevado rendimiento y utilizamos la línea seleccionada “ Solara ” como ejemplo. Además, sugerimos vías de investigación suplementarias para comprender la regulación y el control del contenido de glúcidos de los frutos.

During oil deposition in developing seeds of Arabidopsis, photosynthate is imported in the form of carbohydrates into the embryo and converted to triacylglycerols. To identify genes essential for this process and to investigate the molecular basis for the developmental regulation of oil accumulation, mutants producing wrinkled, incompletely filled seeds were isolated. A novel mutant locus, wrinkled1 (wri1), which maps to the bottom of chromosome 3 and causes an 80% reduction in seed oil content, was identified. Wild-type and homozygous wri1 mutant plantlets or mature plants were indistinguishable. However, developing homozygous wri1 seeds were impaired in the incorporation of sucrose and glucose into triacylglycerols, but incorporated pyruvate and acetate at an increased rate. Because the activities of several glycolytic enzymes, in particular hexokinase and pyrophosphate-dependent phosphofructokinase, are reduced in developing homozygous wri1 seeds, it is suggested that WRI1 is involved in the developmental regulation of carbohydrate metabolism during seed filling

Our aim in this study was to determine how well phenotypic variation in foliar concentrations of carbon-based secondary compounds (CBSCs) in woody plants can be predicted on the basis of two resource-based hypotheses i.e. the carbon-nutrient balance (CNB) and growth-differentiation balance (GDB) hypotheses. We conducted a meta-analysis of literature data with respect to responses of CBSCs, carbohydrates and nitrogen to six types of environmental manipulations (fertilization with nitrogen or phosphorus, shading, CO2 enrichment, drought stress, ozone exposure). Plant responses to nitrogen fertilization, shading and CO2 enrichment in terms of pooled CBSCs and carbohydrates were consistent with predictions made with the two hypotheses. However, among biosynthetically distinct groups of CBSCs only concentrations of phenylpropanoid-derived compounds changed as predicted; hydrolyzable tannins and terpenoids, in particular, were less responsive. Phosphorus fertilization did not affect concentrations of CBSC or primary metabolites. Plant responses to drought and ozone exposure presumably were driven by plant demands for particular types of compounds (osmolites in the case of drought and antioxidants in the case of ozone exposure) rather than by changes in resource availability. Based on the relative importance of the treatment effects, we propose a hierarchical model of carbon allocation to CBSCs. The model implies that CBSC production is determined by both resource availability and specific demand-side responses. However, these two mechanisms work at different hierarchical levels. The domain of the CNB and GDB hypotheses is at the high hierarchical levels, predicting the total amount of carbon that can be allocated to CBSCs. Predicting altered concentrations of individual CBSCs, i.e. low hierarchy levels, probably demands biosynthetically detailed models which also take into account the history of plant interactions with biotic and abiotic factors.

Intake of carbohydrates that provide a large glycemic response has been hypothesized to increase the risk of NIDDM, whereas dietary fiber is suspected to reduce incidence. These hypotheses have not been evaluated prospectively. We examined the relationship between diet and risk of NIDDM in a cohort of 42,759 men without NIDDM or cardiovascular disease, who were 40-75 years of age in 1986. Diet was assessed at baseline by a validated semiquantitative food frequency questionnaire. During years of follow-up, 523 incident cases of NIDDM were documented. The dietary glycemic index (an indicator of carbohydrate's ability to raise blood glucose levels) was positively associated with risk of NIDDM after adjustment for age, BMI, smoking, physical activity family history of diabetes, alcohol consumption, cereal fiber, and total energy intake. Comparing the highest and lowest quintiles, the relative risk (RR) of NIDDM was 1.37 (95% CI, 1.02-1.83, P trend = 0.03). Cereal fiber was inversely associated with risk of NIDDM (RR= 0.70; 95% CI, 0.51-0.96, P trend =0.007; for 8.1 g/day vs. 3.2 g/day). The combination of a high glycemic load and a low cereal fiber intake further increased the risk of NIDDM (RR

Total nonstructural carbohydrates (TNC) of roots were sampled in early autumn from saplings of four species that differ in light-dependent growth and survivorship (\"shade tolerance\"). The two deciduous species (Acer saccharum and Fraxinus americana) had higher TNC concentrations than the evergreens (Tsuga canadensis and Pinus strobus), presumably because of autumn build-up of reserves for spring refoliation. In separate comparisons of deciduous and coniferous pairs, A. saccharum and T. canadensis had higher low-light TNC concentrations and survivorship than F. americana and P. strobus, respectively. In high light, TNC levels were not significantly different between A. saccharum and F. americana and both species had > 98% survivorship. An analytical model of carbohydrate allocation demonstrates that variation in storage allocation can influence survivorship and growth and that the opportunity cost of storage is lower under low light. The model and empirical data are consistent with an observed corelation among species between growth determinancy and shade tolerance and a negative correlation between high-light growth rates and low-light survivorship. Allocation to storage may be an effective strategy of shade tolerance because it is relatively inexpensive under low light and provides a buffer against stresses.

Chromium has been studied since the end of the 19th century, when carcinogenic effects of hexavalent Cr were discovered. Essentiality of trivalent Cr was demonstrated in 1959; Cr3+ has been studied in humans and laboratory animals since the 1970s and it is only since the 1990s that Cr has been studied as an essential element in livestock animals with the same intensity. Trivalent Cr is essential to normal carbohydrate, lipid and protein metabolism. It is biologically active as part of an oligopeptide - chromodulin - potentiating the effect of insulin by facilitating insulin binding to receptors at the cell surface. Cr absorption is low, ranging between 0.4 and 2.0% for inorganic compounds while the availability of organic Cr is more than 10 times higher. Absorbed Cr circulates in blood bound to the beta-globulin plasma fraction and is transported to tissues bound to transferrin. Absorbed Cr is excreted primarily in urine, by glomerular filtration; a small amount is excreted through perspiration, bile and in milk. This review describes Cr metabolism, the different biological functions of Cr and symptoms of Cr deficiency.

Furan and its derivatives were identified in a small number of heat-treated foods back in the 60's and 70's. In May 2004, US Food and Drug Administration published a report on the occurrence of parent furan in a number of thermally treated foods. Since furan has been classified as possibly carcinogenic to human by IARC, a great concern has been addressed to the analysis of this substance naturally-occurring in food. This paper gives a short overview on the mechanistic pathways of the parent furan formation in food by degradation of amino acids and/or reducing sugars, and oxidation of ascorbic acid and polyunsaturated acids which can be induced by thermal or irradiation treatments; further, it deals with the metabolism and toxicology of furan as well as with the comparison of the methods of furan determination.

The healthy lifestyle and appropriate nutrition are stressed nowadays. New foodstuffs are still investigated with the aim to improve the diet and conduce to a better health state of the population. Pseudocereals (amaranth, buckwheat, quinoa) are convenient for this purpose. Their high nutritious and dietary quality meets the demands of the food industry and consumers. Our article deals with quinoa, a commodity from the Andean region, because quinoa is a good source of essential amino acids such as lysine and methionine. Quinoa contains relatively high quantities of vitamins (thiamin, vitamin C) and minerals.