Effect of the Phosphorus-Solubilizing Bacterium Enterobacter Ludwigii on Barley Growth Promotion

Phosphorus (P) is essential for plant growth and development but is often a limiting nutrient in soils. Thus, Pi acquisition from the soil by plant roots is a subject of considerable interest in agriculture. One ecological alternative is the use of P-solubilizing bacteria, which make P available to plants through different mechanisms. Thus, the aim of the present study was to investigate the role of the P-solubilizing bacterium Enterobacter ludwigii in the growth promotion and P content of Hordeum vulgare (barley) under field conditions. Plants were inoculated with E. ludwigii and then its growth promotion effects were compared with those of the reference strain Azospirillum brasilense. The effect of bacterial inoculation showed a beneficial effect on the dry weight, P assimilation and barley yield, especially in E. ludwigii-inoculated plants.  The plant P content at 60 DAS was 38% to 56% higher in E. ludwigii -inoculated plants with respect to non-inoculated plants. The application of bacteria without fertilizer led to the same biological yield (3,795 kg/ha) and increase in one thousand seed weight as the maximum dose of chemical fertilizer applied, while the application of bacteria along with the intermediate fertilizer dose led to a significant increase in grain size (83% of plump grains larger than 2.75 mm wide, whereas 76% of the grains of the control plants reached that size). Endophyte populations of the inoculated bacteria were observed in plants growing under field conditions. The results demonstrated that the inoculation of with E. ludwigii is a promising option to increase P levels in plants and could be a technique for application in agricultural industry

Effect of the phosphorus-solubilizing bacterium Enterobacter ludwigii on barley growth promotion.

Phosphorus (P) is essential for plant growth and development but is often a limiting nutrient in soils. Thus, Pi acquisition from the soil by plant roots is a subject of considerable interest in agriculture. One ecological alternative is the use of P-solubilizing bacteria, which make P available to plants through different mechanisms. Thus, the aim of the present study was to investigate the role of the P-solubilizing bacterium Enterobacter ludwigii in the growth promotion and P content of Hordeum vulgare (barley) under field conditions. Plants were inoculated with E. ludwigii and then its growth promotion effects were compared with those of the reference strain Azospirillum brasilense. The effect of bacterial inoculation showed a beneficial effect on the dry weight, P assimilation and barley yield, especially in E. ludwigii-inoculated plants. The plant P content at 60 DAS was 38% to 56% higher in E. ludwigii -inoculated plants with respect to non-inoculated plants. The application of bacteria without fertilizer led to the same biological yield (3,795 kg/ha) and increase in one thousand seed weight as the maximum dose of chemical fertilizer applied, while the application of bacteria along with the intermediate fertilizer dose led to a significant increase in grain size (83% of plump grains larger than 2.75 mm wide, whereas 76% of the grains of the control plants reached that size). Endophyte populations of the inoculated bacteria were observed in plants growing under field conditions. The results demonstrated that the inoculation of with E. ludwigii is a promising option to increase P levels in plants and could be a technique for application in agricultural industry.Fil: Zaballa, José Ignacio. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Golluscio, Rodolfo. Universidad de Buenos Aires. Facultad de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ribaudo, Claudia Mónica. Universidad de Buenos Aires. Facultad de Agronomía; Argentin

Exposure-lag-response associations between lung cancer mortality and radon exposure in German uranium miners.

Exposure-lag-response associations shed light on the duration of pathogenesis for radiation-induced diseases. To investigate such relations for lung cancer mortality in the German uranium miners of the Wismut company, we apply distributed lag non-linear models (DLNMs) which offer a flexible description of the lagged risk response to protracted radon exposure. Exposure-lag functions are implemented with B-Splines in Cox models of proportional hazards. The DLNM approach yielded good agreement of exposure-lag-response surfaces for the German cohort and for the previously studied cohort of American Colorado miners. For both cohorts, a minimum lag of about 2 year for the onset of risk after first exposure explained the data well, but possibly with large uncertainty. Risk estimates from DLNMs were directly compared with estimates from both standard radio-epidemiological models and biologically based mechanistic models. For age > 45 year, all models predict decreasing estimates of the Excess Relative Risk (ERR). However, at younger age, marked differences appear as DLNMs exhibit ERR peaks, which are not detected by the other models. After comparing exposure-responses for biological processes in mechanistic risk models with exposure-responses for hazard ratios in DLNMs, we propose a typical period of 15 year for radon-related lung carcinogenesis. The period covers the onset of radiation-induced inflammation of lung tissue until cancer death. The DLNM framework provides a view on age-risk patterns supplemental to the standard radio-epidemiological approach and to biologically based modeling

Dynamical Compactification and Inflation in Einstein-Yang-Mills Theory with Higher Derivative Coupling

We study cosmology of the Einstein-Yang-Mills theory in ten dimensions with a quartic term in the Yang-Mills field strength. We obtain analytically a class of cosmological solutions in which the extra dimensions are static and the scale factor of the four-dimensional Friedmann-Lemaitre-Robertson-Walker metric is an exponential function of time. This means that the model can explain inflation. Then we look for solutions that describe dynamical compactification of the extra dimensions. The effective cosmological constant $\lambda_1$ in the four-dimensional universe is determined from the gravitational coupling, ten-dimensional cosmological constant, gauge coupling and higher derivative coupling. By numerical integration, the solution with $\lambda_1=0$ is found to behave as a matter-dominated universe which asymptotically approaches flat space-time, while the solution with a non-vanishing $\lambda_1$ approaches de Sitter space-time in the asymptotic future.Comment: 30 pages, 7 figure

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