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1.
Take-all is a world-wide root-rotting disease of cereals. The causal organism of take-all of wheat is the soil-borne fungus Gaeumannomyces graminis var tritici (Ggt). No resistance to take-all, worthy of inclusion in a plant breeding programme, has been discovered in wheat but the severity of take-all is increased in host plants whose tissues are deficient for manganese (Mn). Take-all of wheat will be decreased by all techniques which lift Mn concentrations in shoots and roots of Mn-deficient hosts to adequate levels. Wheat seedlings were grown in a Mn-deficient calcareous sand in small pots and inoculated with four field isolates of Ggt. Infection by three virulent isolates was increased under conditions which were Mn deficient for the wheat host but infection by a weakly virulent isolate, already low, was further decreased. Only the three virulent isolates caused visible oxidation of Mn in vitro. The sensitivity of Ggt isolates to manganous ions in vitro did not explain the extent of infection they caused on wheat hosts. In a similar experiment four Australian wheat genotypes were grown in the same Mn-deficient calcareous sand and inoculated with one virulent isolate of Ggt. Two genotypes were inefficient at taking up manganese and were very susceptible to take-all, one was very efficient at taking up manganese and was resistant to take-all, and the fourth genotype was intermediate for both characters. All genotypes were equally resistant under Mn-adequate conditions. 相似文献
2.
I Contreras G L Dohm S Abdallah J A Wells N Mooney A Rovira J F Caro 《The Biochemical journal》1990,265(3):887-890
Fasting causes insulin resistance in liver and fat, and increases insulin sensitivity in muscle. We studied the response in vitro and in vivo to insulin of the insulin receptor tyrosine kinase in muscle and liver from 72 h fasted and control rats. Insulin was injected intraperitoneally together with glucose, and blood and tissue samples were obtained 0, 5, 15 and 30 min later. Basal serum glucose and insulin levels were significantly higher in control than in fasting rats. Serum glucose rose to approximately 300 mg/dl at 5 min and then progressively declined without hypoglycaemia. Receptors were prepared from whole tissue by wheat germ lectin affinity chromatography. 125I-insulin binding to purified receptors was increased by fasting in both muscle (18%) and liver (50%). In untreated fasting and control animals, muscle and liver insulin receptor tyrosine kinase activity was stimulated to similar levels by insulin added in vitro. With only insulin treatment in vivo, muscle receptor tyrosine kinase behaved similarly in fasting and control animals with maximal activation at 15 min post injection. In liver, insulin in vivo stimulated receptor tyrosine kinase activity maximally at 5 min post injection in both fasting and control, but in fasting animals the treatment in vivo caused a significantly larger and more prolonged activation of the enzymic activity, possibly due to a decrease in the rate of dephosphorylation and deactivation of the beta subunits. 相似文献
3.
Miren Atristain Daniel von Schiller Aitor Larrañaga Arturo Elosegi 《Restoration Ecology》2023,31(1):e13779
Aging dams and the rising efforts to restore stream ecosystems are increasing the number of dam decommissioning programs. Although dam decommissioning aims at improving in-stream habitat, biodiversity, and ecosystem functioning in the long term, it might also cause ecological impacts in the short term due to the mobilization of the sediment accumulated in the reservoir. Benthic biofilm in particular can be impaired by episodes of high turbidity and scouring. We conducted a multiple before-after/control-impact experiment to assess the effects of the drawdown of a large dam (42 m tall), a first step to its decommissioning, on biofilm structure (biomass and chlorophyll-a) and functioning (metabolism, nutrient uptake, and organic matter breakdown). Our results show that the reservoir drawdown reduced the autotrophic biofilm biomass (chlorophyll-a) downstream from the dam, which in turn lowered metabolism. However, nitrogen and phosphorus uptake by the biofilm was not affected. Organic matter breakdown was slower below the dam than in nearby undammed reaches before and during drawdown. All drawdown effects quickly disappeared and reaches downstream from the dam approached values found in nearby undammed reaches. Thus, our results indicate that the effects of reservoir drawdown on stream biofilms exist but may be small and disappear rapidly. 相似文献
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Aims
Shrub encroachment in mesic grasslands alters the identity and quality of litters entering the system. As litter from shrubs and grasses can differ in their quality, this can lead to differences in litter decomposition by the direct effect of quality, but also to litter interaction during decomposition. The objective of this study was to examine the occurrence of non-additive effects of litter mixtures on the decomposition rates of legume shrub litter (poor in P) or conifer shrub litter (poor in N) and grass litter.Methods
In addition to single litter type litterbags for the three species, we mixed litters of each pair of possible combinations to determine the influence of each species on mass loss. Litterbags were placed in the field and collected after 1, 6, 8, 12 and 24 months. In each collection, litter of each species remaining in mixed bags was separated, dry weighed and analyzed for C, N and P.Results
With respect to shrub litter decomposing alone, mass loss of shrub litter when mixed with grass showed a 9–10 % increase in decomposition rate for conifer and a 3 % increase for legume litter. These litter mixture effects varied with time and they were detected after a decomposition period of 1 year in legume litter and of 2 years in conifer litter.Conclusions
Grass litter hastened conifer and legume litter decomposition in leaf litter mixtures, at least during the first stages of the process. The potential consequences of this result to alter litter accumulation patterns and thus carbon sequestration rates after shrub encroachment into grasslands will depend on whether the observed trends are maintained in the advanced decomposition stages. 相似文献8.
Masaki Unno Albert Ardèvol Carme Rovira Masao Ikeda-Saito 《The Journal of biological chemistry》2013,288(48):34443-34458
Heme oxygenase catalyzes the degradation of heme to biliverdin, iron, and carbon monoxide. Here, we present crystal structures of the substrate-free, Fe3+-biliverdin-bound, and biliverdin-bound forms of HmuO, a heme oxygenase from Corynebacterium diphtheriae, refined to 1.80, 1.90, and 1.85 Å resolution, respectively. In the substrate-free structure, the proximal and distal helices, which tightly bracket the substrate heme in the substrate-bound heme complex, move apart, and the proximal helix is partially unwound. These features are supported by the molecular dynamic simulations. The structure implies that the heme binding fixes the enzyme active site structure, including the water hydrogen bond network critical for heme degradation. The biliverdin groups assume the helical conformation and are located in the heme pocket in the crystal structures of the Fe3+-biliverdin-bound and the biliverdin-bound HmuO, prepared by in situ heme oxygenase reaction from the heme complex crystals. The proximal His serves as the Fe3+-biliverdin axial ligand in the former complex and forms a hydrogen bond through a bridging water molecule with the biliverdin pyrrole nitrogen atoms in the latter complex. In both structures, salt bridges between one of the biliverdin propionate groups and the Arg and Lys residues further stabilize biliverdin at the HmuO heme pocket. Additionally, the crystal structure of a mixture of two intermediates between the Fe3+-biliverdin and biliverdin complexes has been determined at 1.70 Å resolution, implying a possible route for iron exit. 相似文献
9.
Incubation of 14C-labeled substrates continues to be a widely used procedure in soil organic matter (OM) research due to its sensitiveness. When the labeling is found in liquid fractions (soil extracts, hydrolysates), 14C can be easily quantified by using an aliquot for scintillation counting. For this reason, converting a solid carbon sample into liquid form is a typical step for accurate 14C analysis. We have developed an alternative method to carry out this step, which uses standard glass hardware and does not require complex laboratory facilities. Carbon (both in organic or inorganic forms) is converted into CO2 within a reaction vessel connected to a Twisselmann’s extractor with an alkali trap inside. This forms an individual closed chamber (ICC) for each sample, thus eliminating the risk of cross-contaminations. The alkali solution adsorbs the evolved CO2 within the closed system, and the excess of pressure is easily overcome by the use of a balloon. We tested the procedure on a set of substrates and two contrasting soils, checking also the effect of different sample loads (from 20 to 160 mg C) on the CO2 recovery of the process. The percentage of carbon recovered into the alkali (i.e. the efficiency of the process) ranged from 92% for the inorganic C to 93–95% for the organic C method, the latter being sensitive to the amount of sample used for analysis. The ICC method can be successfully applied to analyze 14C-labeling in both carbonates and OM from solid samples, thus representing an alternative method to some established protocols, and it is suitable for substrates with low or very low 14C contents, in which high volumes of sample must be analyzed in order to guarantee representative results. 相似文献
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