Lower NA Research Articles

Geology and geochronology of the Archean plutonic rocks in the northeast Democratic Republic of Congo

Here we report the first regional-scale study of Archean plutonic rocks from 50,000 km2 of the northeast Democratic Republic of Congo (DRC). We include 50 new U-Pb zircon Sensitive High-Resolution Ion MicroProbe (SHRIMP) ages supported by petrographic and whole rock geochemical data from a further ~400 samples, and 39 additional U-Pb zircon ages reported by Kabete et al. (submitted) and Bird (2016).Felsic-intermediate magmatism across the northeast DRC occurred from ~ 3200 to 2530 Ma. Plutonism before ~ 2670 Ma is restricted to the West Nile Gneiss in eastern and northern-most DRC, whereas plutonism across the remainder of the northeast DRC initiated between 2670 and 2640 Ma. Two Neoproterozoic granite plutons ~ 1000–950 Ma are also present within the West Nile Gneiss. Magmatism between ~ 2670 and 2530 Ma marks the principal period of crustal growth in the northeast DRC. Felsic-intermediate plutonism between ~ 2670 and 2600 Ma included two suites of magnesian, calc-alkaline rocks, (1) a sodic-calcic suite with high Sr/Y ratios (>40) comparable with tonalite-trondhjemite-granodiorite (TTG) suites in other Archean terranes, and (2) a calc-alkaline to high-K suite of granitoids with low Sr/Y ratios (<40) and lower Na and Al contents, comparable with “low-Ca” granites in the Yilgarn Craton. In contrast, most granitoids emplaced between ~ 2600 and 2530 Ma have ferroan, high-K calc-alkaline compositions, and are enriched in high field strength (HFSE) and rare Earth elements (REE). Although the HFSE-elevated granitoids are comparable with Closepet-type, and “mafic granites” in other Neoarchean terranes, their volume within the northeast DRC appears unprecedented.Before ~ 2600 Ma partial melting of hydrous metabasalts at depths > 40 km is inferred to have produced the high Sr/Y magnesian granitoids, whereas the low Sr/Y magnesian granitoids were derived from melting-assimilation-storage-hybridization (MASH) processes in the overlying low-mid crust during the same period. Trans-lithospheric extension after ~ 2600 Ma, enabled asthenospheric mantle to interact with the base of the crust, resulting in high-temperature melting that produced the HFSE-elevated granitoids. Inherited Meso- and Paleoarchean zircons are almost completely restricted to the area within 30–40 km of the West Nile Gneiss, implying most of the northeast DRC is underlain by juvenile Neoarchean crust.

Pore-forming transmembrane domains control ion selectivity and selectivity filter conformation in the KirBac1.1 potassium channel.

Potassium (K+) channels are membrane proteins with the remarkable ability to very selectively conduct K+ ions across the membrane. High-resolution structures have revealed that dehydrated K+ ions permeate through the narrowest region of the pore, formed by the backbone carbonyls of the signature selectivity filter (SF) sequence TxGYG. However, the existence of nonselective channels with similar SF sequences, as well as effects of mutations in other regions on selectivity, suggest that the SF is not the sole determinant of selectivity. We changed the selectivity of the KirBac1.1 channel by introducing mutations at residue I131 in transmembrane helix 2 (TM2). These mutations increase Na+ flux in the absence of K+ and introduce significant proton conductance. Consistent with K+ channel crystal structures, single-molecule FRET experiments show that the SF is conformationally constrained and stable in high-K+ conditions but undergoes transitions to dilated low-FRET states in high-Na+/low-K+ conditions. Relative to wild-type channels, I131M mutants exhibit marked shifts in the K+ and Na+ dependence of SF dynamics to higher K+ and lower Na+ concentrations. These results illuminate the role of I131, and potentially other structural elements outside the SF, in controlling ion selectivity, by suggesting that the physical interaction of these elements with the SF contributes to the relative stability of the constrained K+-induced SF configuration versus nonselective dilated conformations.

Contribution of Rhizobium–Legume Symbiosis in Salt Stress Tolerance in Medicago truncatula Evaluated through Photosynthesis, Antioxidant Enzymes, and Compatible Solutes Accumulation

The effects of salt stress on the growth, nodulation, and nitrogen (N) fixation of legumes are well known, but the relationship between symbiotic nitrogen fixation (SNF) driven by rhizobium–legume symbiosis and salt tolerance in Medicago truncatula is not well studied. The effects of the active nodulation process on salt stress tolerance of Medicago truncatula were evaluated by quantifying the compatible solutes, soluble sugars, and antioxidants enzymes, as well as growth and survival rate of plants. Eight weeks old plants, divided in three groups: (i) no nodules (NN), (ii) inactive nodules (IN), and (iii) active nodules (AN), were exposed to 150 mM of NaCl salt stress for 0, 8, 16, 24, 32, 40, and 48 h in hydroponic system. AN plants showed a higher survival rate (30.83% and 38.35%), chlorophyll contents (37.18% and 44.51%), and photosynthesis compared to IN and NN plants, respectively. Improved salt tolerance in AN plants was linked with higher activities of enzymatic and nonenzymatic antioxidants and higher K+ (20.45% and 39.21%) and lower Na+ accumulations (17.54% and 24.51%) when compared with IN and NN plants, respectively. Additionally, higher generation of reactive oxygen species (ROS) was indicative of salt stress, causing membrane damage as revealed by higher electrolyte leakage and lipid peroxidation. All such effects were significantly ameliorated in AN plants, showing higher compatible solutes (proline, free amino acids, glycine betaine, soluble sugars, and proteins) and maintaining higher relative water contents (61.34%). This study advocates positive role of Rhizobium meliloti inoculation against salt stress through upregulation of antioxidant system and a higher concentration of compatible solutes.

Overexpression of β-cyanoalanine synthase of Prunus persica increases salt tolerance by modulating ROS metabolism and ion homeostasis

The β-cyanoalanine synthase (β-CAS) pathway is a principal route for cyanide detoxification in plants. Recent studies suggested that β-CAS plays a pivotal role in plant stress response. However, little is known about the function and the underlying physiological mechanism of β-CAS under salt stress in perennial trees. Here we report the identification and functional characterization of PpCAS1 isolated from peach (Prunus persica). Transcripts of PpCAS1 were dramatically induced by salt and dehydration stress. Ectopic overexpression of PpCAS1 in Nicotiana benthamiana enhanced salinity tolerance, whereas down-regulation of PpCAS1 in P. persica through virus-induced gene silencing led to elevated salt sensitivity. The PpCAS1-overexpressing lines accumulated less reactive oxygen species (ROS) than the controls due to higher activities of antioxidant enzymes and expression levels of related genes. Moreover, the overexpression lines contained lower levels of Na+, higher levels of K+, thus lower Na+ : K+ ratios than the controls. When PpCAS1 was silenced, the levels of ROS and Na+ : K+ ratio were changed in an opposite manner. Additionally, the transcripts of genes involved in salt overly sensitive signaling pathway were significantly up-regulated in PpCAS1-overexpressing tobacco lines, but down-regulated in PpCAS1-silenced peach plants, compared to the corresponding controls. Altogether, our results demonstrate that PpCAS1 positively regulates salt tolerance in peach plants through the modulation of ROS and ion homeostasis.

Chemical and boron isotopic compositions of tourmaline at the Dachang Sn-polymetallic ore district in South China: Constraints on the origin and evolution of hydrothermal fluids

The Dachang Sn-polymetallic ore district in South China is the second largest tin district in the world with a tin reserve of over one million tonnes. Zn-Cu skarn and stratiform, massive, and vein Sn-Pb-Zn ores are all present in this district. This has led to a debate as to whether the Sn orebodies were formed by Cretaceous magmatic-hydrothermal replacement or Devonian submarine exhalative-hydrothermal sedimentation. Here, we present a systematic investigation of the major, trace element, and boron isotopic compositions of different types of tourmaline in the Dachang ore district. Tourmaline disseminated in the Longxianggai granite and pegmatite veins belongs to the schorl series and has high contents of Li, Zn, and Ga. The δ11B value of primary magma of the Longxianggai granite is estimated to be about −13‰, close to the global average δ11B value (−11‰) for S-type granites. Tourmaline from quartz-tourmaline veins in the Longxianggai granite has similar chemical composition to the magmatic tourmaline and likely formed from hydrothermal fluids exsolved from the evolved granitic melt. The δ11B value of the initial hydrothermal fluids is also calculated to be about −13‰. Tourmalines from the skarn and sulfide ores in the Lamo deposit have higher Mg/(Mg+Fe) and lower Na/(Na+Ca) ratios and higher contents of Be, Ge, Sr, and Sn than magmatic tourmaline. These patterns likely reflect input of elements derived from the host Devonian limestone. The δ11B values of the hydrothermal fluids are estimated to be between −13 and −10‰, suggesting evolved magmatic-hydrothermal fluids related to the Longxianggai granite. Tourmalines from the stratiform and vein ores in the Changpo-Tongkeng deposit are extremely Mg-rich and mostly belong to the dravite series. They have high contents of Sc, V, Cr, Sr, and Sn and show positive Eu anomalies. The δ11B values of these B- and Sn-rich fluids are estimated to be between −15 and −10‰, suggesting that the fluids also have a magmatic-hydrothermal origin. These fluids are most likely derived from the same granitic magma source, but may have interacted with the Devonian volcanic rocks.

Variations in ion transportation and accumulation in alfalfa plants under NaCl and Na2HCO3 stresses with different pH levels

AbstractFor revealing the effects of NaCl and NaHCO3 stress at different pH levels on the absorption and accumulation of main ions in roots, stems and leaves, alfalfa (Medicago sativa L.) plants were cultivated in a nutrient solution system. After NaCl and Na2HCO3 imposition, the contents of main ions in roots, stems, leaves and xylem bleeding sap were determined. Under NaCl and Na2HCO3 stresses with the same Na+ concentration, Na2HCO3 stress showed severer inhibitory effects on alfalfa growth in contrast to NaCl stress at different pH levels. Under NaCl stresses at different pH levels, alfalfa plants showed much lower Na+ accumulation and Na+ delivery rate in root bleeding sap than that under NaHCO3 stress. The plants of NaHCO3 stress showed a severer inhibition in K+ accumulation, lower K+ delivery rate, but higher Na+/K+ ratios than the plants of NaCl stress. NaHCO3 stress increased Ca2+ and Mg2+ accumulation in alfalfa roots, decreased Ca2+ and Mg2+ delivery rates and increased leaf Na+/Ca2+ ratio and Na+/Mg2+ ratio. Both NaCl and NaHCO3 stresses decreased the contents of Fe3+ and Mn2+ in roots, but increased the contents of Cu2+ in roots, stems and leaves, the content of Mn2+ in stems and leaf Zn2+ content in alfalfa plants. However, the contents of Fe3+ and Mn2+ in roots and stem Mn2+ content in the NaHCO3 treatments were much lower than those in the NaCl treatments. In conclusion, NaHCO3 stress produced severer injury and induced severer Na+ toxicity to alfalfa plants than NaCl stress. The effects of NaHCO3 stress and NaCl stress on the absorption and accumulation of trophic ions were different. Under NaCl stress, the increased pH did not alter Na+ absorption and accumulation in plants, but altered the distribution of some nutrient ions in roots, stems and leaves.

Identification and Characterization of Wheat Germplasm for Salt Tolerance.

Salinity is one of the limiting factors of wheat production worldwide. A total of 334 internationally derived wheat genotypes were employed to identify new germplasm resources for salt tolerance breeding. Salt stress caused 39, 49, 58, 55, 21 and 39% reductions in shoot dry weight (SDW), root dry weight (RDW), shoot fresh weight (SFW), root fresh weight (RFW), shoot height (SH) and root length (RL) of wheat, respectively, compared with the control condition at the seedling stage. The wheat genotypes showed a wide genetic and tissue diversity for the determined characteristics in response to salt stress. Finally, 12 wheat genotypes were identified as salt-tolerant through a combination of one-factor (more emphasis on the biomass yield) and multifactor analysis. In general, greater accumulation of osmotic substances, efficient use of soluble sugars, lower Na+/K+ and a higher-efficiency antioxidative system contribute to better growth in the tolerant genotypes under salt stress. In other words, the tolerant genotypes are capable of maintaining stable osmotic potential and ion and redox homeostasis and providing more energy and materials for root growth. The identified genotypes with higher salt tolerance could be useful for developing new salt-tolerant wheat cultivars as well as in further studies to underline the genetic mechanisms of salt tolerance in wheat.

Effect of irrigation salinity and ecotype on the growth, physiological indicators and seed yield and quality of Salicornia europaea

The euhalophyte species Salicornia europaea is cultivated for oilseed and as a fodder crop in various parts of the world. In saline coastal environments it possesses great potential for the subsistence of the most disadvantaged farmers. We investigated the effect of salinity levels in irrigation water on the germination capacity, shoot biomass and seed productivity as well as diverse quality traits (nitrogen content in shoots and seeds and fatty acids, in seeds) and physiological traits (stable carbon and nitrogen isotopes and ion content) of two accessions collected in the United Arab Emirates (UAE). The three salinity levels tested were irrigation with fresh water (0.3 dS m−1), brackish water (25 dS m−1) and sea water (40 dS m−1). In addition, a hypersaline condition (80 dS m−1) was also tested for germination. The best germination rates were achieved with seeds exposed to fresh and brackish water, while imbibition with sea water decreased germination by half and hypersaline water inhibited it almost totally. However, the best irrigation regime in terms of biomass and seed yield involved brackish water. Moreover, rising salinity in the irrigation increased the stable isotope composition of carbon (δ13C) and nitrogen (δ15N), together with the Na+ and K+ of shoots and seeds, and the lipid levels of seeds, while the total nitrogen content and the profile of major fatty acids of seeds did not change. Differences between the two ecotypes existed for growth and seed yield with the best ecotype exhibiting lower δ13C and higher K+ in both shoots and seeds, lower Na+ and higher δ15N in shoots, and lower N in seeds, together with differences in major fatty acids. Physiological mechanisms behind the response to irrigation salinity and the ecotypic differences are discussed in terms of photosynthetic carbon and nitrogen metabolism.

How to Choose a Hydrological Recovery Mode for Degraded Semiarid Wetland in China? A Case Study on Restoration of Phragmites australis Saline-Alkaline Wetland

Hydrological recovery is the basis for restoring the structure and function of wetlands in semiarid and arid areas of China. Selecting an appropriate hydrological recovery mode may be helpful for improving the effectiveness of wetland restoration. We conducted pot experiments to study the effects of the flooding frequency, duration, depth, and occurrence time on the height, biomass, ion contents, and photosynthetic physiology of Phragmites australis in degraded saline–alkaline marsh in the West Songnen Plain, China. At the end of the growing season, we found that the biomass, photosynthetic parameters, and water use efficiency (WUE) of the leaves increased, whereas the Na+ concentration decreased, and the K+ content remained unchanged under an increased flooding frequency treatment. As the flooding depth increased, the plant height increased, but there were no differences in the photosynthetic parameters, biomass, and WUE under flooding at 5 cm and 10 cm. Under different flooding duration treatments, the plant height and biomass were greater, but the photosynthetic parameters and Na+ and K+ contents were lower under a flooding duration of three months. The flooding occurrence time had little effect on the growth of P. australis. Our results indicate that the flooding frequency and duration had greater effects than the flooding depth and occurrence time in the hydrological recovery model for P. australis restoration. The biomass accumulated by P. australis was related to lower Na+ contents and the maintenance of a high K+/Na+ contents, and WUE increased by adjusting photosynthesis under a moderate flooding frequency and duration. These results have important implications for the restoration of degraded semiarid wetlands with man-made channel systems in conditions with limited freshwater resources.

Soil Properties Affected Vegetation Establishment and Persistence on Roadsides

Vegetation along roadsides reduces soil erosion, increases filtering of water runoff, and acts as a biodiversity corridor. The purpose of this study was to assess soil properties and evaluate their effect on vegetation establishment in roadsides. Furthermore, the effects of shoulder type (paved and unpaved) and time since seeding (0–1 year, 2–4 years, and ≥ 5 years) on soil properties were also evaluated. Roadside soil was sampled from 53 sites in three regions (Panhandle, Southcentral, and Southeastern) in Nebraska, USA. The soil was analyzed for pH, Na, Cl, electrical conductivity, exchangeable sodium percentage, and bulk density and heavy metals. At each site, vegetation was classified into one of four categories, (1) 50% plant canopy cover dominated by weedy annual grasses and forbs; and (4) > 50% plant canopy cover dominated by seeded perennial grasses. Sodium concentration exceeded the limits that can cause vegetation growth decline in all regions. Sodium and soil bulk density in all regions were clustered with the < 10% plant canopy cover category, meaning that these clustered soil properties have a significant influence on the amount of bare ground and establishment/persistence of vegetation. Heavy metal concentrations (lead, arsenic, zinc, cadmium, and nickel) were less than the thresholder in all regions. It was observed that 12–44% of roadside sites had less than 50% vegetation cover. Roadside soils of paved shoulders had lower Na and Cl concentrations than the roadside soils of unpaved shoulders. The 0–1 year since seeding had higher cadmium, arsenic, and nickel concentrations compared to ≥ 5 years since seeding. Soil degradation declined vegetation establishment along highways, and the degree of soil degradation of these roadsides varied depending on shoulder types and time since seeding.

Amorphous NaVOPO 4 as a High-Rate and Ultrastable Cathode Material for Sodium-Ion Batteries

The low cost and profusion of sodium resources make sodium-ion batteries (SIBs) a potential alternative to lithium-ion batteries for grid-scale energy storage applications. However, the use of conv...

Molecular hydrogen–induced salinity tolerance requires melatonin signalling inArabidopsis thaliana

Melatonin (MT) plays positive roles in salinity stress tolerance. However, the upstream signalling components that regulate MT are poorly understood. Here, we report that endogenous MT acts downstream of molecular hydrogen (H2 ) in the salinity response in Arabidopsis. The addition of hydrogen-rich water and expression of the hydrogenase1 gene (CrHYD1) from Chlamydomonas reinhardtii increased endogenous H2 and MT levels and enhanced salinity tolerance. These results were not observed in the absence of serotonin N-acetyltransferase gene (SNAT). H2 increased the levels of SNAT transcripts in the wild-type and CrHYD1 lines, which had lower Na+ /K+ ratios and higher levels of ion transport-related gene transcripts. These changes were not observed in atsnat/CrHYD1-4 hybrids. The increased MT-dependent Na+ extrusion observed in the CrHYD1 plants resulted, at least in part, from enhanced Na+ /H+ antiport across the plasma membrane. The endogenous H2 -induced MT-dependent regulation of ion and redox homeostasis was impaired in the atsnat/CrHYD1-4 hybrids. Taken together, these results demonstrate that MT-induced salinity tolerance is induced by a H2 signalling cascade that regulates ion and redox homeostasis in response to salinity.

Chitosan regulates metabolic balance, polyamine accumulation, and Na+ transport contributing to salt tolerance in creeping bentgrass

BackgroundChitosan (CTS), a natural polysaccharide, exhibits multiple functions of stress adaptation regulation in plants. However, effects and mechanism of CTS on alleviating salt stress damage are still not fully understood. Objectives of this study were to investigate the function of CTS on improving salt tolerance associated with metabolic balance, polyamine (PAs) accumulation, and Na+ transport in creeping bentgrass (Agrostis stolonifera).ResultsCTS pretreatment significantly alleviated declines in relative water content, photosynthesis, photochemical efficiency, and water use efficiency in leaves under salt stress. Exogenous CTS increased endogenous PAs accumulation, antioxidant enzyme (SOD, POD, and CAT) activities, and sucrose accumulation and metabolism through the activation of sucrose synthase and pyruvate kinase activities, and inhibition of invertase activity. The CTS also improved total amino acids, glutamic acid, and γ-aminobutyric acid (GABA) accumulation. In addition, CTS-pretreated plants exhibited significantly higher Na+ content in roots and lower Na+ accumulation in leaves then untreated plants in response to salt stress. However, CTS had no significant effects on K+/Na+ ratio. Importantly, CTS enhanced salt overly sensitive (SOS) pathways and also up-regulated the expression of AsHKT1 and genes (AsNHX4, AsNHX5, and AsNHX6) encoding Na+/H+ exchangers under salt stress.ConclusionsThe application of CTS increased antioxidant enzyme activities, thereby reducing oxidative damage to roots and leaves. CTS-induced increases in sucrose and GABA accumulation and metabolism played important roles in osmotic adjustment and energy metabolism during salt stress. The CTS also enhanced SOS pathway associated with Na+ excretion from cytosol into rhizosphere, increased AsHKT1 expression inhibiting Na+ transport to the photosynthetic tissues, and also up-regulated the expression of AsNHX4, AsNHX5, and AsNHX6 promoting the capacity of Na+ compartmentalization in roots and leaves under salt stress. In addition, CTS-induced PAs accumulation could be an important regulatory mechanism contributing to enhanced salt tolerance. These findings reveal new functions of CTS on regulating Na+ transport, enhancing sugars and amino acids metabolism for osmotic adjustment and energy supply, and increasing PAs accumulation when creeping bentgrass responds to salt stress.

NaCl cotransporter activity and Mg2+ handling by the distal convoluted tubule.

The genetic disease Gitelman syndrome, knockout mice, and pharmacological blockade with thiazide diuretics have revealed that reduced activity of the NaCl cotransporter (NCC) promotes renal Mg2+ wasting. NCC is expressed along the distal convoluted tubule (DCT), and its activity determines Mg2+ entry into DCT cells through transient receptor potential channel subfamily M member 6 (TRPM6). Several other genetic forms of hypomagnesemia lower the drive for Mg2+ entry by inhibiting activity of basolateral Na+-K+-ATPase, and reduced NCC activity may do the same. Lower intracellular Mg2+ may promote further Mg2+ loss by directly decreasing activity of Na+-K+-ATPase. Lower intracellular Mg2+ may also lower Na+-K+-ATPase indirectly by downregulating NCC. Lower NCC activity also induces atrophy of DCT cells, decreasing the available number of TRPM6 channels. Conversely, a mouse model with increased NCC activity was recently shown to display normal Mg2+ handling. Moreover, recent studies have identified calcineurin and uromodulin (UMOD) as regulators of both NCC and Mg2+ handling by the DCT. Calcineurin inhibitors paradoxically cause hypomagnesemia in a state of NCC activation, but this may be related to direct effects on TRPM6 gene expression. In Umod-/- mice, the cause of hypomagnesemia may be partly due to both decreased NCC expression and lower TRPM6 expression on the cell surface. This mini-review discusses these new findings and the possible role of altered Na+ flux through NCC and ultimately Na+-K+-ATPase in Mg2+ reabsorption by the DCT.

Quantifying Alloy 625 Crevice Corrosion using an Image Differencing Technique: Part II. A Diffusive Transport Model of Crevice Cation Concentration using Surface Current Density

In this paper we present a diffusive transport model of alloy 625 crevice corrosion for simulated ocean water. The model uses the empirical electrochemical kinetics (local surface current density) and empirical damage profile to determine the source of cations from surface oxidation reactions and then calculates the total cation concentration in the crevice solution as a function of time. To gain insight into the solution speciation at the calculated cation concentrations, a thermodynamic software package was used. In those calculations, it was assumed that the anodic dissolution products of the individual alloy components form their corresponding metal salts in the crevice solution. The calculations, based on activity, predicted that precipitation occurred in the same time frame as the experimentally observed increase in active area, decrease in surface current density and transition to diffusion control. The salts that precipitated out of the model solution were NaCl, at 5.3 m, and NiCl2·6H2O, at 5.7 m. It is shown that the presence of the Cr3+, Fe2+, Mo3+ and Nb5+ in the model crevice solution increase the cation and chloride activities resulting in precipitation at the same Ksp values as in the pure salts, albeit at lower Na+ or Ni2+ concentrations. Implications of the speciation results as they relate to actual crevices are discussed.

Effects of KF and RbF treatments on Cu(In,Ga)Se2-based solar cells: A combined photoelectron spectroscopy and DFT study

In this work, the alkali-induced chemical and electronic modifications observed at the KF- and RbF-treated Cu(In,Ga)Se2 (CIGSe)/CdS interfaces are correlated to a Density Functional Theoretical (DFT) model of the alkali metal induced point defects at a CuInSe2/CdS interface. Analysed with hard X-ray photoelectron spectroscopy (HAXPES), the near-interface regions showed a Cu-poor, In-rich and stoichiometric CdS composition for the KF-CIGSe/CdS interface and a Cu-poor, In, S-rich composition for the RbF-CIGSe/CdS interface. The DFT-calculated defect formation energies and valence band offsets (VBO) at the defect-induced interfaces indicate towards possible formation of specific defects at the KF- and RbF-treated CIGSe/CdS interfaces. Cu vacancies indicated by the Cu-poor stoichiometry of the alkali-treated interfaces contribute to an increase in the acceptor densities (NA). Possible formation of KCu and RbCu defects could result in lower NA at the interfaces because of the Cu vacancies being filled up by K and Rb atoms. NaCd and excess CdCu defects at the KF-CIGSe/CdS interface and only CdCu defects at the RbF-CIGSe/CdS interface might have formed that would result in higher donor densities (ND) at the interfaces. These factors, which showed enhanced type-inversion when applied in device simulations, resulted in fill factor (FF) and open-circuit voltage (Voc) gains in devices.

Salt‐tolerant broomcorn millet ( Panicum miliaceum L.) resists salt stress via modulation of cell wall biosynthesis and Na + balance

Soil salinization threatens sustainable agricultural production and ecological balance in many parts of the world. Therefore, to breed plants with salt tolerance and discover the resistance genes are essential for enhancing salt tolerance adaptation. We studied phenotypic, physiological characteristics, and digital RNA sequencing of two broomcorn millet cultivars (salt tolerant cultivar, ST 47; salt sensitive cultivar, SS 212), stressed by 1% NaCl (w/w; ~170 mM) for 0, 12 hr, 1, 3, 7 days and subsequent re-watering 7 days (RW 7 days). By comparative phenotype and physiology analysis we suggest ST 47 showed greater salt tolerance and faster recovery after re-watering than SS 212, and lower Na+ contents and higher K+/Na+ ratio. Digital RNA sequencing analysis suggested 6,878 and 1,940 differentially expressed genes (DEGs) were detected in ST 47 at 12 hr (vs. 0 hr) and RW 7 days (vs. 0 hr), respectively, whereas 7,246 and 5,375 DEGs were identified in SS 212. DEG functional enrichments suggested ST 47 exhibited better regulation of phenylpropanoid biosynthesis, carbon metabolism, and auxin and gibberellin signal transduction in response to salt stress via enhancing the cell wall biosynthesis. Furthermore, ionic stress signaling analysis proposed ST 47 better regulation of Na+ distribution in response to salt stress. These results provide valuable information for improving salinity tolerance in plants and studying the function of candidate genes governing salt tolerance in broomcorn millet.

Root-mediated acidification and resistance to low calcium improve wheat (Triticum aestivum) performance in saline-sodic conditions

Salinity represents a medium with high soluble salts where as sodicity represents a medium with high exchangeable sodium, low calcium and highly alkaline pH. Salinity and sodicity commonly occur together in salt-affected soils however physiological studies have mostly considered salinity alone ending up in poor field success of the selected genetic resources. Similarly, the role of root-mediated acidification in salt resistance is not known in wheat. Here six wheat genotypes were exposed to salinity (NaCl: 125 mM), low calcium (25% of non-treated control) and salinity + low calcium in solution culture. There were significant differences among the wheat genotypes for growth and leaf ionic composition under salinity, low calcium and salinity + low calcium treatments. The wheat genotypes SARC-1, 25-SAWSN-42 and Pasban-90 accumulated higher K+ and Ca2+ and lower Na+ and Cl− and were resistant to the combined stress of low calcium and salinity.These genotypes also showed higher root-mediated acidification under stress conditions. The wheat genotypes resistant to salinity + low calcium supply in solution culture also performed better in the saline-sodic soil in a lysimeter study. A genotype resistant to salinity alone accumulated lower Ca2+ and showed lower rhizosphere acidification potential and did not perform good in saline-sodic soil conditions. Therefore, root-mediated acidification potential and resistance to low calcium supply improves resistance of wheat to saline-sodic conditions. It is further suggested that screening of the wheat germplasm for saline-sodic soils should be carried out at salinity + low calcium to better simulate saline-sodic field conditions.

CBL4-CIPK5 pathway confers salt but not drought and chilling tolerance by regulating ion homeostasis

Calcineurin B-like protein (CBL) and CBL-interacting protein kinase (CIPK) play an important role in regulation on plant abiotic stress tolerance. It is unknown whether CBL-CIPK pathway regulates abiotic stress tolerance in bermudagrass. In the present study, CdtCBL4 and CdtCIPK5 from triploid bermudagrass were characterized. CdtCBL4 and CdtCIPK5 transcripts were induced by dehydration and salt. In addition, low temperature induced CdtCIPK5 transcript, but inhibited CdtCBL4 transcript; ABA induced CdtCIPK5 transcript, but had no influence on CdtCBL4 transcript. Yeast two-hybrid and bimolecular fluorescence complementation (BiFC) assay demonstrated CdtCIPK5 interacted with CdtCBL4. Overexpression of CdtCIPK5 and CdtCBL4 improved salt tolerance in transgenic rice compared with wild type, based on measurements on relative water content (RWC), chlorophyll content and Fv/Fm. CdtCIPK5 and CdtCBL4 overexpressing transgenic lines had a lower Na+ accumulation and a higher K+/Na+ ratio under salt stress. The higher transcript levels of OsNHX3, OsHKT1;1, OsHKT1;4, OsHKT1;5 were observed in CdtCIPK5 overexpressing plants than in WT. It is suggested that CdtCBL4-CdtCIPK5 pathway confers salinity tolerance by upregulating OsNHX3, OsHKT1;1, OsHKT1;4, OsHKT1;5 expression for maintenance of Na+/K+ homeostasis during salt stress.

Crosstalk of phenylpropanoid biosynthesis with hormone signaling in Chinese cabbage is key to counteracting salt stress

Salt stress limits the regional distribution of Chinese cabbage, yet the molecular factors that confer tolerance to salt stress in Chinese cabbage remain poorly understood. To further investigate this issue, salt-tolerant and salt-sensitive Chinese cabbage cultivars were selected, and their responses to salt stress were tested. Then, comparative transcriptome profiling was performed on the roots of salt-tolerant and salt-sensitive Chinese cabbage cultivars under salt stress. The results showed that Qinghua and Biyu are considered to be salt-tolerant and salt-sensitive Chinese cabbage cultivars, respectively. Qinghua had higher water content and lower Na+/K+ in roots and leaves, better root development, higher lignin content and higher abscisic acid content in roots than Biyu. Comparative transcriptome profiling showed that the abscisic acid and ethylene signaling pathways of Qinghua roots were more actively expressed than those of Biyu. During root adaptation to salt stress, abscisic acid crosstalk with suberin biosynthesis and ethylene signaling crosstalk with lignin biosynthesis were observed. Suberin development and lignin accumulation in the Qinghua roots were found to be important strategies for resisting salt stress in this study. These strategies are not independent, but rather coordinate to promote salt tolerance in Chinese cabbage. The increased lignin content in the roots of Qinghua under salt stress may prevent embolism. Embolism prevention can maintain the flow of water transport, and thus compensate for the reduction in water permeability of these suberized cells in a process that occurs concurrently with greater sodium ion limitation. These results provide novel insight into the crosstalk of phenylpropanoid biosynthesis with hormone signaling under salt stress, and facilitate further dissection of molecular mechanism of adaptive response to salt stress in Chinese cabbage.