Effective temperatures of red giants in the APOKASC catalogue and the mixing length calibration in stellar models

Red giants in the updated APOGEE-Kepler catalogue, with estimates of mass, chemical composition, surface gravity and effective temperature, have recently challenged stellar models computed under the standard assumption of solar calibrated mixing length. In this work, we critically reanalyse this sample of red giants, adopting our own stellar model calculations. Contrary to previous results, we find that the disagreement between the effective temperature scale of red giants and models with solar calibrated mixing length disappears when considering our models and the APOGEE-Kepler stars with scaled solar metal distribution. However, a discrepancy shows up when alpha-enhanced stars are included in the sample. We have found that assuming mass, chemical composition and effective temperature scale of the APOGEE-Kepler catalogue, stellar models generally underpredict the change of temperature of red giants caused by alpha-element enhancements at fixed [Fe/H]. A second important conclusion is that the choice of the outer boundary conditions employed in model calculations is critical. Effective temperature differences (metallicity dependent) between models with solar calibrated mixing length and observations appear for some choices of the boundary conditions, but this is not a general resultComment: 8 pages, 10 figures, Astronomy & Astrophysics, in pres

The Near Infrared NaI Doublet Feature in M Stars

The NaI near-infrared doublet has been used to indicate the dwarf/giant population in composite systems, but its interpretation is still a contentious issue. In order to understand the behaviour of this controversial feature, we study the observed and synthetic spectra of cool stars. We conclude that the NaI infrared feature can be used as a dwarf/giant discriminator. We propose a modified definition of the NaI index by locating the red continuum at 8234 angstrons and by measuring the equivalent width in the range 8172-8197 angstrons, avoiding the region at lambda > 8197 angstrons, which contains VI, ZrI, FeI and TiO lines. We also study the dependence of this feature on stellar atmospheric parameters.Comment: 9 pages, (TeX file) + 7 Figures in Postscript format. Accepted for publication in The Astrophysical Journa

Selenium biofortification in the 21st century: status and challenges for healthy human nutrition

Background: Selenium (Se) is an essential element for mammals and its deficiency in the diet is a global problem. Plants accumulate Se and thus represent a major source of Se to consumers. Agronomic biofortification intends to enrich crops with Se in order to secure its adequate supply by people. Scope: The goal of this review is to report the present knowledge of the distribution and processes of Se in soil and at the plant-soil interface, and of Se behaviour inside the plant in terms of biofortification. It aims to unravel the Se metabolic pathways that affect the nutritional value of edible plant products, various Se biofortification strategies in challenging environments, as well as the impact of Se-enriched food on human health. Conclusions: Agronomic biofortification and breeding are prevalent strategies for battling Se deficiency. Future research addresses nanosized Se biofortification, crop enrichment with multiple micronutrients, microbial-integrated agronomic biofortification, and optimization of Se biofortification in adverse conditions. Biofortified food of superior nutritional quality may be created, enriched with healthy Se-compounds, as well as several other valuable phytochemicals. Whether such a food source might be used as nutritional intervention for recently emerged coronavirus infections is a relevant question that deserves investigation

Effective temperatures of red giants in the APOKASC catalogue and the mixing length calibration in stellar models

Red giants in the updated APOGEE-Kepler catalogue, with estimates of mass, chemical composition, surface gravity and effective temperature, have recently challenged stellar models computed under the standard assumption of solar calibrated mixing length. In this work, we critically reanalyse this sample of red giants, adopting our own stellar model calculations. Contrary to previous results, we find that the disagreement between the effective temperature scale of red giants and models with solar calibrated mixing length disappears when considering our models and the APOGEE-Kepler stars with scaled solar metal distribution. However, a discrepancy shows up when alpha-enhanced stars are included in the sample. We have found that assuming mass, chemical composition and effective temperature scale of the APOGEE-Kepler catalogue, stellar models generally underpredict the change of temperature of red giants caused by alpha-element enhancements at fixed [Fe/H]. A second important conclusion is that the choice of the outer boundary conditions employed in model calculations is critical. Effective temperature differences (metallicity dependent) between models with solar calibrated mixing length and observations appear for some choices of the boundary conditions, but this is not a general resul

Mapping of QTLs associated with biological nitrogen fixation traits in soybean.

Biological nitrogen fi xation (BNF) is a key process, but despite the economic and environmental importance, few studies about quantitative trait loci (QTL) controlling BNF traits are available, even in the economically important crop soybean Glycine max (L.) Merr. In this study, a population of 157 F 2:7 RILs derived from crossing soybean cultivars Bossier (high BNF capacity) and Embrapa 20 (medium BNF capacity) was genotyped with 105 simple sequence repeat markers (SSRs). The genetic map obtained has 1231.2 cM and covers about 50% of the genome, with an average interval of 18.1 cM. Three traits, nodule number (NN), the ratio nodule dry weight (NDW)/NN and shoot dry weight (SDW) were used to evaluate BNF performance. A composite interval mapping for multiple traits method (mCIM) analysis mapped two QTLs for SDW (LGs E and L), three for NN (LGs B1, E and I), and one for NDW/NN (LG I); all QTLs were of small effect (R 2 -values ranging from 1.7% to 10.0%) and explained 15.4%, 13.8% and 6.5% of total variation for these three traits, respectively

Short-term responses to salinity of soybean and chenopodium album grown in single and mixed-species hydroponic systems

Weeds account for losses in crop yields, and this event might be exacerbated by salinity. Therefore, we investigated the responses of Chenopodium album L. and soybean (Glycine max (L.) Merr.) to salt stress, as well as interferences between species. Ten-day old plants were grown for 1 week in a single- or mixed-species set-up, either with or without 100 mM of NaCl. C. album reduced the biomass of soybean similarly to salt stress, while its growth was unaffected under any condition. C. album decreased the crop protein content when salinity was applied. This effect was ascribed to altered protein metabolism and/or N usage to produce other N metabolites, including osmolytes. The two species did not reciprocally affect the capacity to accumulate Na+, but the weed contained two-fold more Na+ in the leaves. Elevated initial K+ concentration and high K+ delivery to the shoot likely explained the better acclimation of C. album to salinity. C. album produced more phenolics and proline and exhibited greater antioxidant activity, but low lipid peroxidation, in the mixed set-up under salinity. Thus, it is possible that the weed could become more resilient to salinity when growing in a soybean field. In the long term, this might cause significant losses in soybean productivity as expected by the dramatic decline in crop protein content