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941.
Wang Ruzhen Wu Hui Sardans Jordi Li Tianpeng Liu Heyong Peñuelas Josep Dijkstra Feike A. Jiang Yong 《Plant and Soil》2020,457(1-2):407-420
Plant and Soil - Soil aggregates constitute spatially-separated microbial habitats and architectural units for biogeochemical reactions. However, little is known about how aggregates varying in... 相似文献
942.
943.
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944.
H. Deckmyn L. Font C. Van Hemelen L.O. Carreras G. Defreyn J. Vermylen 《Life sciences》1983,33(15):1491-1497
Aortae from fetal or 3 weeks old rats produced very small amounts of PGI2, prostacyclin. This production increased from 4 weeks on, reaching adult values at about ten weeks. This maturation seemed to be predominantly determined by a change in the PGI2 synthetase system, rather than in arachidonic acid availability, phospholipase or cyclo-oxygenase activity. The anti-oxidant ascorbic acid stimulated prostacyclin production more strongly in adult than in young rat aortae. This finding suggests that the lower production of PGI2 by young tissues is not due to an enhanced inhibition of prostacyclin synthetase by lipid peroxides. 相似文献
945.
Increasing drought decreases phosphorus availability in an evergreen Mediterranean forest 总被引:9,自引:2,他引:7
Mediterranean ecosystems are water-limited and frequently also nutrient-limited. We aimed to investigate the effects of increasing
drought, as predicted by GCM and eco-physiological models for the next decades, on the P cycle and P plant availability in
a Mediterranean forest. We conducted a field experiment in a mature evergreen oak forest, establishing four drought-treatment
plots and four control plots (150 m2 each). After three years, the runoff and rainfall exclusion reduced an overall 22% the soil moisture, and the runoff exclusion
alone reduced it 10%. The reduction of 22% in soil moisture produced a decrease of 40% of the accumulated aboveground plant
P content, above all because there was a smaller increase in aerial biomass. The plant leaf P content increased by 100 ± 40
mg m−2 in the control plots, whereas it decreased by 40 ± 40 mg m−2 in the drought plots. The soil Po-NaHCO3 (organic labile-P fraction) increased by 25% in consonance with the increase in litterfall, while the inorganic labile-P
fraction decreased in relation to the organic labile-P fraction up to 48%, indicating a decrease in microbial activity. Thus,
after just three years of slight drought, a clear trend towards an accumulation of P in the soil and towards a decrease of
P in the stand biomass was observed. The P accumulation in the soil in the drought plots was mainly in forms that were not
directly available to plants. These indirect effects of drought including the decrease in plant P availability, may become
a serious constraint for plant growth and therefore may have a serious effect on ecosystem performance. 相似文献
946.
Jorge A. Fernández Josep Bonet-Ávalos Josep M. Poblet 《Inorganica chimica acta》2010,363(15):4368-4373
We report a detailed analysis of the electronic structure and results of molecular dynamics simulations for the large polyoxomolybdate [H3Mo57V6(NO)6O183(H2O)18]21− (Mo57V6) which is a highly symmetric anion with a complex electronic structure and exhibiting a unique variety of multifunctionality. The six vanadium centres are reduced with one electron each, the six Mo centres are bonded to non-innocent NO ligands and the additional six 4d electrons are mostly delocalised over the rest of molybdenum atoms. DFT calculations carried out with the solvent - modelled by a continuum approach - suggest that despite the large charge of the anion, the Mo57V6 framework can be easily reduced in polar solvents. Furthermore, the Mo57V6 cluster has 18 water molecules trapped in its internal cavity. Molecular dynamics simulations carried out with different solvent conditions suggest that the water molecules inside the cavity have a high ordered structure over a wide range of temperatures and give important information about the cluster anion interactions with the cations present in solution. The obtained results allow a better understanding of related properties of the giant ball-shaped polyoxometalates/Keplerates as the present cluster contains similar building blocks - like the (metal)6O6 type pores with crown ether-like structure. 相似文献
947.
A combination of traditional and emerging methodologies was used to assess the trade-offs between several life-history traits (linked to reproduction and condition) and parasitism in a commercially-exploited cold-water species, blue whiting Micromesistius poutassou, in the Mediterranean Sea. The use of histological and gravimetric methods revealed conflicting evidence as to the fecundity type (indeterminate or determinate) of this species. Moreover, there seem to be condition-mediated compensations between egg quality and egg quantity. The effects of parasitism on reproduction and condition are species-specific and occur mainly at high intensities of infection; they include a lower batch fecundity (affecting reproductive potential), a higher hepatosomatic index and a higher spleen-somatic index. Considering the fact that larger fish spawn more eggs and that the minimum landing size is lower than the size at maturity, these results may have implications for the future management of M. poutassou stocks in the Mediterranean Sea. Local environmental conditions may account for geographical differences regarding infection in M. poutassou. Altogether, the results support the idea that the complex trade-offs between parasitism, reproduction and condition need to be considered in order to understand the status of cold-water species such as M. poutassou. 相似文献
948.
J Carreras J Bosch J Mezquita 《Comparative biochemistry and physiology. B, Comparative biochemistry》1982,71(1):57-63
1. The three phosphoglycerate mutase isozymes from mammals (types M, B and MB isozymes) differ in their sensitivity to the - SH group reagents. 2. Rabbit muscle phosphoglycerate mutase (type M isozyme) is reversibly inactivated by tetrathionate, rho-chloromercuribenzoate and Hg2+. 3. Titration with rho-chloromercuribenzoate shows the existence of two sulfhydryl groups per enzyme subunit, the modification of which produces a progressive decline in enzyme activity. 4. The apparent Km values for substrate and cofactor are not affected by tetrathionate treatment. 5. Phosphoglycerate mutase inactivated by tetrathionate and by rho-chloromercuribenzoate is unable to form the functionally active phosphorylenzyme when mixed with glycerate-2,3-P2, and is not protected by the cofactor against heating. 6. Glycerate-2,3-P2 protects against tetrathionate treatment, but fails to protect against Hg2+ and rho-chloromercuribenzoate inactivation. 相似文献
949.
950.
Federica Amici Filippo Aureli Roger Mundry Alejandro Sánchez Amaro Abraham Mesa Barroso Jessica Ferretti Josep Call 《Primates; journal of primatology》2014,55(3):447-457
Little evidence of calculated reciprocity has been found in non-human primates so far. In this study, we used a simple experimental set-up to test whether partners pulled a sliding table to altruistically provide food to each other in short-term interactions. We tested 46 dyads of chimpanzees, bonobos, gorillas, orangutans, brown capuchin monkeys and spider monkeys to examine whether a subject’s tendency to provide food to a partner was directly affected by the partner’s previous behaviour, by the species, by the condition (i.e., whether the partner could access the food provided by the subject) and by the social tolerance levels within each dyad. Chimpanzees and orangutans were the only species pulling significantly more when the partner could retrieve the food altruistically provided. However, no species reciprocated food exchanges, as subjects’ probability to pull was not affected by the previous number of the partner’s pulls, with the possible exception of one orangutan dyad. Although subjects clearly knew how the apparatus worked and easily obtained food for themselves, individuals did not usually take the opportunity to provide food to their partners, suggesting that calculated reciprocity is not a common behaviour and that food exchanges are usually not reciprocated in the short-term within dyads. 相似文献