Gametophytic cross-incompatibility systems in corn have been the subject of genetic studies for more than a century. They have tremendous economic potential as a genetic mechanism for controlling fertilization without controlling pollination. Three major genetically distinct and functionally equivalent cross-incompatibility systems exist inZea mays:Ga1,Tcb1, andGa2. All three confer reproductive isolation between maize or teosinte varieties with different haplotypes at any one locus. These loci confer genetically separable functions to the silk and pollen: a female function that allows the silk to block fertilization by non-self-type pollen and a male function that overcomes the block of the female function from the same locus. Identification of some of these genes has shed light on the reproductive isolation they confer. The identification of both male and female factors as pectin methylesterases reveals the importance of pectin methylesterase activity in controlling the decision between pollen acceptance versus rejection, possibly by regulating the degree of methylesterification of the pollen tube cell wall. The appropriate level and spatial distribution of pectin methylesterification is critical for pollen tube growth and is affected by both pectin methylesterases and pectin methylesterase inhibitors. We present a molecular model that explains how cross-incompatibility systems may function that can be tested inZeaand uncharacterized cross-incompatibility systems. Molecular characterization of these loci in conjunction with further refinement of the underlying molecular and cellular mechanisms will allow researchers to bring new and powerful tools to bear on understanding reproductive isolation inZea maysand related species.

We present a chemodynamical study of the Grus I ultra-faint dwarf galaxy (UFD) from medium-resolution (R similar to 11,000) Magellan/IMACS spectra of its individual member stars. We identify eight confirmed members of Grus I, based on their low metallicities and coherent radial velocities, and four candidate members for which only velocities are derived. In contrast to previous work, we find that Grus I has a very low mean metallicity of <[Fe/H]> = -2.62 +/- 0.11 dex, making it one of the most metal-poor UFDs. Grus I has a systemic radial velocity of -143.5 +/- 1.2 km s(-1) and a velocity dispersion of sigma(rv) = 2.5(-0.8)(+1.3) km s(-1), which results in a dynamical mass of M(1/2()r(h)) = 8(-4)(+12) 2 x 10(5) M-circle dot and a mass-to-light ratio of M/L-V = 440(-250)(+650) M-circle dot/L-circle dot. Under the assumption of dynamical equilibrium, our analysis confirms that Grus I is a dark-matter-dominated UFD (M/L> 80 M-circle dot/L-circle dot). However, we do not resolve a metallicity dispersion (sigma([Fe/H]) < 0.44 dex). Our results indicate that Grus I is a fairly typical UFD with parameters that agree with mass-metallicity and metallicity-luminosity trends for faint galaxies. This agreement suggests that Grus I has not lost an especially significant amount of mass from tidal encounters with the Milky Way, in line with its orbital parameters. Intriguingly, Grus I has among the lowest central densities ( rho(1/2) similar to 3.5(-2 1)(+5.7) x 10(7) M-circle dot kpc(-3))of the UFDs that are not known to be tidally disrupting. Models of the formation and evolution of UFDs will need to explain the diversity of these central densities, in addition to any diversity in the outer regions of these relic galaxies.

Core formation may modify the stable isotopic signatures for both the mantles and cores of differentiated planetary bodies. We performed high P-T experiments with a piston-cylinder apparatus at 1 GPa and 1873-2073 K to determine the Cr isotopic fractionation factor during metal-silicate segregation. Experimental results consistently indicate that the metal phase is isotopically heavier than the coexisting silicate phase, with Delta Cr-53(metal-sliicate) up to 0.3 parts per thousand at the investigated experimental conditions. Oxygen fugacity, silicate composition, and S content in the metal phase do not have significant effects on the Cr isotopic fractionation factor. By contrast, increasing Ni content in the metal increases the Cr-53(metal-sliicate) value, implying that the Ni content of the core could influence planetary isotopic signatures. We conclude that heavier Cr isotopes enter the core preferentially during planetary core formation. The delta Cr-53 value of the terrestrial mantle could be lowered by up to similar to 0.02 parts per thousand by core formation, despite that this is within current analytical uncertainty of chondritic Cr isotopic composition. For smaller bodies such as the Moon, Mars, and Vesta, the lower core formation temperatures could potentially generate a resolvable coremantle Cr isotopic fractionation. However, the Moon's small core size would limit the change in the Cr isotopic composition of the lunar mantle compared to chondritic. For Vesta and Mars, core formation could lower the delta Cr-53 values of their mantles by similar to 0.01-0.02 parts per thousand, which is trivial relative to the analytical uncertainty. On the other hand, core formation could increase the delta Cr-53 values of the cores of the parent bodies of iron meteorites by up to similar to 0.2 parts per thousand at 1873 K. Therefore, the significantly heavy Cr isotopic composition (up to 2.85 parts per thousand) of iron meteorites cannot be explained by equilibrium fractionation between the core and the mantle of the parent bodies of iron meteorites. (C) 2022 Elsevier B.V. All rights reserved.

The iron-silicon phase diagram has been established at the conditions of Mercury's core. The resulting phase diagram is remarkably complex, and presents an array of new mechanisms which may power Mercury's inner dynamo.

Diamond anvil cell techniques have been improved to allow access to the multimegabar ultrahigh-pressure region for exploring novel phenomena in condensed matter. However, the only way to determine crystal structures of materials above 100 GPa, namely, X-ray diffraction (XRD), especially for low Z materials, remains nontrivial in the ultrahigh-pressure region, even with the availability of brilliant synchrotron X-ray sources. In this work, we perform a systematic study, choosing hydrogen (the lowest X-ray scatterer) as the subject, to understand how to better perform XRD measurements of low Z materials at multimegabar pressures. The techniques that we have developed have been proved to be effective in measuring the crystal structure of solid hydrogen up to 254 GPa at room temperature [C. Ji et al., Nature 573, 558-562 (2019)]. We present our discoveries and experiences with regard to several aspects of this work, namely, diamond anvil selection, sample configuration for ultrahigh-pressure XRD studies, XRD diagnostics for low Z materials, and related issues in data interpretation and pressure calibration. We believe that these methods can be readily extended to other low Z materials and can pave the way for studying the crystal structure of hydrogen at higher pressures, eventually testing structural models of metallic hydrogen. (C) 2020Author(s).

Globally, soils store two to three times as much carbon as currently resides in the atmosphere, and it is critical to understand how soil greenhouse gas (GHG) emissions and uptake will respond to ongoing climate change. In particular, the soil-to-atmosphere CO(2)flux, commonly though imprecisely termed soil respiration (R-S), is one of the largest carbon fluxes in the Earth system. An increasing number of high-frequencyR(S)measurements (typically, from an automated system with hourly sampling) have been made over the last two decades; an increasing number of methane measurements are being made with such systems as well. Such high frequency data are an invaluable resource for understanding GHG fluxes, but lack a central database or repository. Here we describe the lightweight, open-source COSORE (COntinuous SOil REspiration) database and software, that focuses on automated, continuous and long-term GHG flux datasets, and is intended to serve as a community resource for earth sciences, climate change syntheses and model evaluation. Contributed datasets are mapped to a single, consistent standard, with metadata on contributors, geographic location, measurement conditions and ancillary data. The design emphasizes the importance of reproducibility, scientific transparency and open access to data. While being oriented towards continuously measuredR(S), the database design accommodates other soil-atmosphere measurements (e.g. ecosystem respiration, chamber-measured net ecosystem exchange, methane fluxes) as well as experimental treatments (heterotrophic only, etc.). We give brief examples of the types of analyses possible using this new community resource and describe its accompanying R software package.

The influence of atmosphere pollution on human health is receiving more and more concerns as strengthened anthropogenic activity had brought excessive pollutant into the atmosphere. To date, the quantitative estimation about the contribution of atmosphere on the accumulation of heavy metal in the edible cereal parts induced by anthropogenic forcing is scarce. Taking the Yangtze River Delta area, China as an example, this study estimates quantitatively the influence of atmosphere on the concentration of heavy metal in the aboveground wheat tissues induced by anthropogenic industrial activity at the regional scale. The results show that the aboveground wheat tissues in the southern Yangtze River Delta area accumulated much more heavy metals than that in the northern area, although there is no significant difference in the geological and climate conditions, soil types, agricultural manages, wheat cultivar and soil heavy metals concentrations (even heavy metals concentrations in wheat mot) between the southern area and northern area. The mean concentrations of Pb, Zn, Cu and Cd in wheat grain in southern area have exceeded the thresholds of contamination levels. The present study suggests that the influence of atmosphere on the accumulation of Hg, Cd, Pb, Zn, Cu, Ni and Cr in the aboveground wheat tissues is greatly significant when high amounts of pollutant are measured in the atmosphere. Based on translocation coefficient of the element, it is estimated that atmospheric pollution induced by anthropogenic forcing might lead to the concentration of heavy metals in wheat straw and grain increase by approximately 100% and 354% (Hg), 64% and 293% (Pb), 122% and 160% (Cr), 50% and 38% (Cd) and 14% and 41% (Cu), respectively.

Trace elements play a crucial role in the growth and health of organisms. Imaging the distribution of trace elements in organisms at micron resolution scale can reveal the chemical form and transfer mechanism of trace elements in organisms and their influence on the growth of organisms. In the present study, we used a high-resolution secondary ion mass spectrometer (NanoSIMS) to image the trace elements zinc (Zn), iron (Fe), magnesium (Mg) and potassium (K) in the wheat grain and analyzed the chemical form of Zn. The NanoSIMS images indicate that the micro-distributions of Zn, Fe, Mg and K in the wheat grain are similar, especially for Zn and Fe, mostly in the phytate granules of the aleurone and closely associated with P and H-O. Besides being distributed in phytate granules, some or a small amount of Mg and K are also distributed in starch granules of the endosperm. The S and C-N distributions are very similar, mainly in the protein matrix of the endosperm and aleurone. P and H-O, rather than S and C-N, are the two dominant ligands to Zn, Fe, K and Mg in wheat grain. The dominant chemical form of Zn and Fe in the wheat grain is in the phytate, not the protein. The P is crucial to Zn, Fe, Mg and K accumulation in the wheat, and agricultural producers should pay special attention to adjust the application of P fertilizer to affect the concentrations of Zn in the crop. In situ imaging of NanoSIMS can elucidate the relations between trace elements in grain samples with clear visualization, and it also has great significance in chemical analysis, crop breeding and environmental monitoring.

The viscosity of iron alloy liquids is the key for the core dynamo and core-mantle differentiation of terrestrial bodies. Here we measured the viscosity of Fe-Ni-C liquids up to 7 GPa using the floating sphere viscometry method and up to 330 GPa using first-principles calculations. We found a viscosity increase at similar to 3-5 GPa, coincident with a structural transition in the liquids. After the transition, the viscosity reaches similar to 14-27 mPa center dot s, a factor of 2-4 higher than that of Fe and Fe-S liquids. Our computational results from 5 to 330 GPa also indicate a high viscosity of the Fe-Ni-C liquids. For a carbon-rich core in large terrestrial body, the level of turbulence in the outer core would be lessened approaching the inner core boundary. It is also anticipated that Fe-Ni-C liquids would percolate in Earth's deep silicate mantle at a much slower speed than Fe and Fe-S liquids.

Jovian planet formation has been shown to be strongly correlated with host-star metallicity, which is thought to be a proxy for disk solids. Observationally, previous works have indicated that Jovian planets preferentially form around stars with solar and supersolar metallicities. Given these findings, it is challenging to form planets within metal-poor environments, particularly for hot Jupiters that are thought to form via metallicity-dependent core accretion. Although previous studies have conducted planet searches for hot Jupiters around metal-poor stars, they have been limited due to small sample sizes, which are a result of a lack of high-quality data making hot-Jupiter occurrence within the metal-poor regime difficult to constrain until now. We use a large sample of halo stars observed by TESS to constrain the upper limit of hot-Jupiter occurrence within the metal-poor regime (-2.0 <= [Fe/H] <= -0.6). Placing the most stringent upper limit on hot-Jupiter occurrence, we find the mean 1 sigma upper limit to be 0.18% for radii 0.8-2 R (Jupiter) and periods 0.5-10 days. This result is consistent with previous predictions indicating that there exists a certain metallicity below which no planets can form.