Uptake Of Na Research Articles

The mayfly Neocloeon triangulifer senses decreasing oxygen availability (PO2) and responds by reducing ion uptake and altering gene expression.

Oxygen availability is central to the energetic budget of aquatic animals and may vary naturally and/or in response to anthropogenic activities. Yet, we know little about how oxygen availability is linked to fundamental processes such as ion transport in aquatic insects. We hypothesized and observed that ion (22Na and 35SO4) uptake would be significantly decreased at O2 partial pressures below the mean Pcrit (5.4 kPa) where metabolic rates (MO2) are compromised, and ATP production is limited. However, we were surprised to observe marked reductions in ion uptake at oxygen partial pressures well above the Pcrit, where MO2 was stable. For example, SO4 uptake decreased by 51% at 11.7kPa, and 82% at the Pcrit (5.4kPa) while Na uptake decreased by 19% at 11.7kPa, and 60% at the Pcrit. Nymphs held for longer time periods at reduced PO2 exhibited stronger reductions in ion uptake rates. Fluids from whole body homogenates exhibited a 29% decrease in osmolality in the most hypoxic condition. The differential expression of atypical guanylyl cyclase (gcy-88e) in response to changing PO2 conditions provides evidence for its potential role as an oxygen sensor. Several ion transport genes (e.g., chloride channel and sodium-potassium ATPase) and hypoxia-associated genes (e.g., ldh and egl-9) were also impacted by decreased oxygen availability. Together, our work suggests that N. triangulifer can sense decreased oxygen availability and perhaps conserves energy accordingly, even when MO2 is not impacted.

γ-Aminobutyric acid enhances salt tolerance by sustaining ion homeostasis in apples

Soil salinization had become a global ecological problem, which restricts the plant growth, and the quantity and quality of fruits. As a signaling molecule, γ-Aminobutyric acid (GABA) mediates a series of physiological processes and stress responses. Our previous research showed that GABA could alleviate drought, low phosphorus, cadmium stresses in apples, but the further research about its physiological mechanisms under salt stress was even more needed. The present study showed that the inhibition of salt stress on plant growth might be effectively alleviated by the treatment of 0.5 mM GABA, and the osmotic balance and photosynthetic capacity of plants could be maintained. Exogenous GABA could effectively inhibit the enrichment of reactive oxygen species and the uptake of Na+, while maintaining ion homeostasis. The experiment results indicated GABA could markedly promote the expression amount of Na+ and K+ transport-related genes (e.g., HKT1, AKT1, NHX1, SOS1, SOS2, and SOS3) in apples under salt stress. Overexpression and interference (RNAi) of MdGAD1 in apple roots, which is a crucial enzyme in the GABA biosynthesis, affected the salt tolerance of plants. Transgenic apple plants with roots of overexpression MdGAD1 showed less relative electrolyte leakage and more expression level of related ion transport genes than CK group, but RNAi MdGAD1 led to the opposite results. These results indicated that GABA accumulation could effectively strengthen the resistance of apple plants to salt stress and alleviate the injury of apple seedlings resulted from salinity.

NaCl stress, tissue specific Na+ and K+ up-take and their effect on growth and physiology of Helianthus annuus L. and Solanum lycopersicum L.

Salinity is one of the major abiotic stresses that can threat plant growth and yield. Helianthus annuus L. and Solanum lycopersicum L. are economically important crops and widely cultivated, but the uptake of Na+ and K+ during the NaCl stress in their above and below ground parts is not well-understood. The main objective of this study was to understand the response of leaf structure and function to different concentrations of NaCl and to understand the Na+ and K+ uptake in H. annuus and S. lycopersicum. Four different concentrations of NaCl (H. annuus; 50 mM, 100 mM, 150 mM, 200 mM, and S. lycopersicum; 25 mM, 50 mM, 75 mM, 100 mM) were applied. Plant Biomass and the leaf structure and function (leaf area, midrib length, secondary vein length, petiole diameter, photosynthesis, stomatal conductance, transpiration, and intrinsic water use efficiency) were studied. We found that the salinity concentration of more than 150 mM in H. annuus and 75 mM in S. lycopersicum significantly reduced the plant height and leaf performance. At the same time, the yield (seed and fruit weight) decreased at 100 mM and 50 mM of NaCl concentration of H. annuus and S. lycopersicum, respectively. Maximum Na+ and K+ were accumulated in roots and stem in H. annuus and roots and fruits in S., lycopersicu. At the same time, the minimum Na+ and K+ were detected in seeds of H. annuus and fruit and root of S. lycopersicum. The K+: Na+ showed variation in both crops. We conclude that the vegetative parts of Helianthus annuus can tolerate up to 150 mM and S. lycopersicum up to 75 mM of NaCl concentration. The concentration of Melatonin increases as the stress level increases as it acts to remove the stress. These findings can be helpful to cultivate the Helianthus annuus and S. lycopersicum in saline areas and can also be useful to cultivate other crops when the successive cultivation of both crops is practiced and Na+ is absorbed by the crop from the soil.

Defense mechanisms of alfalfa against cyclic tetramethylene tetranitramine (HMX) stress

Much attention has been paid to the environmental toxicity and ecological risk caused by cyclic tetramethylene tetranitramine (HMX) pollution in military activity sites. In this study, the response mechanism of alfalfa plants to HMX was analyzed from the aspects of the photosynthetic system, micromorphology, antioxidant enzyme system, mineral metabolism, and secondary metabolism, in order to improve the efficiency of plant restoration. Exposure to 5 mg·L−1 HMX resulted in a significant increase in leaf N content and a significant increase and drift of the Fourier transform infrared protein peak area. Transmission electron microscopy images revealed damage to the root system subcellular morphology, but the plant leaves effectively resisted HMX pressure, and the photosynthetic parameters essentially maintained steady-state levels. The root proline content decreased significantly by 23.1–47.2 %, and the root reactive oxygen species content increased significantly by 1.66–1.80 fold. The roots regulate the transport/absorption of many elements that impart stress resistance, and Cu, Mn, and Na uptake is significantly associated with secondary metabolism. The metabolism of roots was upregulated in general by HMX exposure, with the main differences appearing in the content of lipids and lipid-like molecules, further confirming damage to the root biofilm structure. HMX causes an imbalance in the energy supply from oxidative phosphorylation in roots and generates important biomarkers in the form of pyrophosphate and dihydrogen phosphate. Interestingly, HMX had no significant effect on basic metabolic networks (i.e., glycolysis/gluconeogenesis and the tricarboxylic acid cycle), confirming that alfalfa has good stress resistance. Alfalfa plants apparently regulate multiple network systems to resist/overcome HMX toxicity. These findings provide a scientific basis for improving plant stress tolerance and understanding the HMX toxicity mechanism.

The effect of halotolerant bacteria isolated from saline soil on the growth and yield of maize in saline soil

<p>Salinity is a common problem of abiotic stress in the world. Salinity stress causes yield loss in cultivated crops, such as maize. The yield of maize exposed to salinity stress can be increased with the application of some beneficial microorganisms. Three isolates of halotolerant bacteria from saline fields can potentially be used as biostimulants (plant growth-promoting rhizobacteria). A field experiment to study the effect of halotolerant bacteria isolates application on the growth and yield of maize (<em>Zea mays</em> L.) in saline soil was arranged in a randomized block design with a combination of isolate types and frequency applications, and it was repeated three times. In this study, four bacterial strains used were SN13 (<em>Streptomyces </em>sp.), SN22 (<em>Bacillus megaterium</em>), SN23 (<em>Bacillus</em> sp.) and SN26 (<em>Bacillus aryabhattai</em>) isolated from the soil of saline-prone regions of Lamongan, in coastal East Java, Indonesia. Results indicated that an application of halotolerant bacteria was able to improve the yield and nutrient uptake of maize in saline soil. However, the application of halotolerant bacteria significantly improved leaf total chlorophyll content (105.94%), plant dry weight (56.14%), Grain weight per cob (108.11%) and had a positive trend in increasing N uptake (61.19%), and Na uptake (73.09%) compared to control. It is concluded that the application of halotolerant bacteria is able to alleviate the salinity stress of maize in saline soil.</p>

Effect of different nutrient management practices on nutrient availability and uptake in Vaikom kari soils of Kuttanad, Kerala

A field experiment was laid out in RBD with 16 treatments in three replications with rice variety Uma. The treatments were dolomite, lime + MgSO4 or Rice Husk Ash (RHA) + MgSO4 along with 100% package of practice recommendations of Kerala Agricultural University (POP) alone or with 100% POP + foliar spray of 13:0:45 (1%) or borax (0.5%) or 13:0:45 + borax at PI stage. Lime + MgSO4 + 75% POP + 13:0:45 + borax as well as lime without MgSO4 + 100% POP combined with 13:0:45 or borax or both were also included as treatments. The treatment dolomite + POP + 13:0:45 produced the highest grain yield of 5.42 and 5.57 t ha-1 during 2015 and 2016 respectively. This treatment was followed by dolomite + POP + 13:0:45 + borax and lime + POP + MgSO4 + 13:0:45 during both the years. Lower yields were produced by the treatments involving RHA and 75% POP. The pooled analysis of two years' data also proved the significance of the treatments involving dolomite + POP or lime + POP + MgSO4 on grain yield. The highest yield of 5.49 t ha-1 was recorded by dolomite + POP + 13:0:45 followed by dolomite + POP + 13:0:45 + borax and lime + MgSO4 + POP + 13:0:45. The treatments involving RHA and 75% POP registered significantly lower grain yield in the pooled data. The treatments involving dolomite registered lower status of soil available Fe and higher status of available Mn and B. Higher status of available Zn was registered by the treatments involving dolomite or lime + MgSO4. The treatments involving dolomite, lime + MgSO4 or RHA + MgSO4 along with POP registered higher available Cu in the soil. Dolomite treatments recorded lower status of Na and exchangeable Al in the soil. Dolomite or lime + MgSO4 along with POP + 13:0:45 with or without borax registered higher uptake of Fe, Mn and Zn while dolomite + POP + 13:0:45 with or without borax recorded higher uptake of Cu and B. The treatments involving RHA and 75% POP recorded lower uptake of micronutrients during both the years. Uptake of Na was the highest with RHA + POP + MgSO4 + 13:0:45 during first year and with dolomite + POP during second year. Higher Al uptake was observed with lime + POP + 13:0:45 with or without MgSO4. The grain yield was significantly and positively correlated with the uptake of Mn, Zn, Cu and B and significantly and negatively correlated with Fe during the first year. During the second year, the yield was significantly and positively correlated with uptake of nutrients except Na and Al. The results indicated that amelioration of soil acidity is a crucial management practice for improving the availability and uptake of nutrients resulting in higher yield.

Assessment of Salinity Tolerance in Greengram [Vigna radiata (L.) Wilczek

Background: Greengram is one of the important and salt sensitive food legume crops with high nutritional quality. The area under salinity is increasing gradually due to various reasons like global warming, continues irrigation of bore well water and use of more organic fertilizers etc. Identification of salinity tolerant genotype in greengram is highly essential to improve the production and productivity. Salinity stress condition increases the absorption of more Na+ whereas the reduction of K+ absorption was noticed, which thus decreases the K+ /Na+ ratio. The first visible symptom due to salinity stress was retarded growth because of more uptake of Na+ ions leads to reduction of physiological activities. The next important character affected by salinity stress was radical growth. Methods: A total of 20 greengram genotypes were evaluated for salinity tolerance under four EC levels. Screening was done by roll towel method with two replications. The roll towels were placed in different buckets filled with different EC level of saline water and observations were recorded on the 8th day of germination. Result: The salinity level of more than 4.0 EC dsm-1 causes gradual reduction in radicle length and at 12.0 EC level almost in all the genotypes the radicle length was reduced to half as compare to control. The correlation analysis indicated that the plumule length and radicle length were the important criteria for selection to salinity tolerance. While observing the other growth parameters like plumule and radical length reduction, dry matter weight and salinity tolerance and susceptible index the genotypes IPMD 14-10 and VGG 17-038 were identified as more tolerant genotypes and DGGV 80, PUSA-BM5 and VBN 4 were more sensitive genotypes.

A novel high-affinity potassium transporter SeHKT1;2 from halophyte Salicornia europaea shows strong selectivity for Na+ rather than K.

High-affinity K+ transporters (HKTs) are known as transmembrane cation transporters and are involved in Na+ or Na+-K+ transport in plants. In this study, a novel HKT gene SeHKT1;2 was isolated and characterized from the halophyte, Salicornia europaea. It belongs to subfamily I of HKT and shows high homology with other halophyte HKT proteins. Functional characterization of SeHKT1;2 indicated that it contributes to facilitating Na+ uptake in Na+-sensitive yeast strains G19, however, cannot rescue the K+ uptake-defective phenotype of yeast strain CY162, demonstrating SeHKT1;2 selectively transports Na+ rather than K+. The addition of K+ along with NaCl relieved the Na+ sensitivity. Furthermore, heterologous expression of SeHKT1;2 in sos1 mutant of Arabidopsis thaliana increased salt sensitivity and could not rescued the transgenic plants. This study will provide valuable gene resources for improving the salt tolerance in other crops by genetic engineering.

Coupling Effects of Potassium Fertilization Rate and Application Time on Growth and Grain Yield of Wheat (Triticum aestivum L.) Plants Grown Under Cd-Contaminated Saline Soil

Potassium is an essential macronutrient, where its availability regulates numerous biochemical, phenological, and physiological responses in plants. Synchronizing potassium supply with plant demand is a key factor to enhance growth and grain production of wheat grown in cadmium-contaminated saline soils. Field experiments were conducted in El Fayoum province, Egypt, between latitudes 29° 02′ and 29° 35′ N and longitudes 30° 23′ and 31° 05′ E, during the cropping seasons of 2017–2018 and 2018–2019 to determine the influence of different applied potassium rates and times on nutrient uptake and wheat yield grown under Cd-contaminated saline soil (ECe = 8.53 dS m−1 and Cd = 18 mg kg−1 soil). Four K levels (K0, K40, K80, and K120 representing 0, 40, 80, and 120 kg ha−1) were applied at different application times [full dose (basal) at sowing (100% S), two equal split doses at sowing and flowering stage (50% S + 50% F), and full dose at flowering stage (100% F)]. The experimental treatments were arranged in a randomized split complete block design and replicated three times. The applied K rates, times, and their interaction induced significant differences in nutrient uptake and physiological responses which in turn improved the growth and yield of the wheat crop. Potassium addition with 120 kg ha−1 at two equal split doses (50% S + 50% F) resulted in the highest values of plant height (97 cm), Fv/Fm (0.83), PI (5.49), SPAD (58.63), MSI (34.57), seed yield (5.04 t ha−1), straw yield (9.04 t ha−1), and water productivity (0.99 kg m−3). Similarly, the uptake of N, P, K, Ca, Mg, Fe, Mn, and Zn was increased, while the uptake of Na and Cd decreased as the K supply increased under the split application. The addition of potassium by 120 kg ha−1 in two equal split doses at the sowing and flowering stage could be a valuable approach to improve yield and yield quality of wheat crop grown under cadmium-contaminated saline soils.

Transcriptome analysis reveals molecular mechanisms underlying salt tolerance in halophyte Sesuvium portulacastrum.

Soil salinity is an important environmental problem that seriously affects plant growth and crop productivity. Phytoremediation is a cost-effective solution for reducing soil salinity and potentially converting the soils for crop production. Sesuvium portulacastrum is a typical halophyte which can grow at high salt concentrations. In order to explore the salt tolerance mechanism of S. portulacastrum, rooted cuttings were grown in a hydroponic culture containing ½ Hoagland solution with or without addition of 400 mM Na for 21 days. Root and leaf samples were taken 1 h and 21 days after Na treatment, and RNA-Seq was used to analyze transcript differences in roots and leaves of the Na-treated and control plants. A large number of differentially expressed genes (DEGs) were identified in the roots and leaves of plants grown under salt stress. Several key pathways related to salt tolerance were identified through KEGG analysis. Combined with physiological data and expression analysis, it appeared that cyclic nucleotide gated channels (CNGCs) were implicated in Na uptake and Na+/H+ exchangers (NHXs) were responsible for the extrusion and sequestration of Na, which facilitated a balance between Na+ and K+ in S. portulacastrum under salt stress. Soluble sugar and proline were identified as important osmoprotectant in salt-stressed S. portulacastrum plants. Glutathione metabolism played an important role in scavenging reactive oxygen species. Results from this study show that S. portulacastrum as a halophytic species possesses a suite of mechanisms for accumulating and tolerating a high level of Na; thus, it could be a valuable plant species used for phytoremediation of saline soils.

Na uptake at TiO2 anatase surfaces under electric field control: A first-principles study

Na-ion batteries (NIBs) are promising devices for large-scale energy-storage facilities. Nanostructured TiO2 is an efficient NIB negative electrode, showing good cycling performance and rate capability, but its activity depends on the crystalline facets exposed by anatase nanoparticles. Hence, we propose here a DFT+U study of Na+ adsorption and insertion at (101), (100) and (001)-TiO2 surfaces under the influence of external electric fields, which are simulated by adding a sawtooth-like electrostatic potential to the bare ionic potential. We find that field polarization affects Na+ uptake as well as titania electronic features, promoting redox processes within Ti sublattice, as in battery charge/discharge cycling. Our results highlight the high-energy (001) surface to be the most active, for both directions of external fields, proving its activity to be exerted reversibly. Besides further insights, these outcomes pave the route for further exploration and design of electrode materials by simulation of battery in operando conditions.Graphical

Endogenous nitric oxide contributes to chloride and sulphate salinity tolerance by modulation of ion transporter expression and reestablishment of redox balance in Brassica napus cultivars

Salinity is an adverse environmental stress for crop plants and the mechanism of salinity tolerance and its interaction with phytohormone like nitric oxide (NO) is still lacking, especially for Na2SO4 in B. napus. Therefore, in the present study, B. napus cultivars were grown under equimolar concentrations of NaCl/Na2SO4 and with their anions (KCl/K2SO4), to discriminate toxic responses of different types of salts on growth, oxidative stress, antioxidant defense, anion concentration and endogenous production of NO. Results showed that plant growth, photosynthetic rate and pigments productions were strongly inhibited under Na+ dominated salt treatments (NaCl/Na2SO4). As a result, production of oxidative stress (H2O2, O2.-, MDA, EL) related parameters were significantly induced under these treatments. The uptake of Na+ was high in B. napus cultivars irrespective of chloride/sulphate anions presence. However, Cl- and SO42- anions accumulation was only high in sensitive cultivars. The differential responses of B. napus cultivars against salinity treatments were associated with endogenous production of NO. The tolerant cultivar maintained higher level of NO, while sensitive cultivars experience a reduction in NO and inhibition of its biosynthesis enzymes, upon exposure to salinity treatments. To prove NO involvement, NO scavenger was applied on the leaves of B. napus cultivars, which significantly induced salt toxicity symptoms, oxidative stress and upregulated gene expression of ion transporters and uptake of Na+, Cl- and SO42-. Conversely, application of NO donor (sodium nitroprusside) reversed the salinity induce oxidative stress, ion accumulation and stimulated antioxidant defense in B. napus cultivars. Thus, the present study shows that endogenous NO level could act as an essential signaling molecule for triggering and activating the salinity adaptive response in rapeseed and Na+ toxicity plays a dominate role in growth inhibition, while the additive effect of chloride/sulphate anions may be cultivar dependent.

Assessment of selenium contribution to salt and water stress tolerance in hydroponically grown cotton (Gossypium barbadense L.)

Selenium (Se) is a trace element but its basic role in plant physiology is still poorly known. An experiment to investigate the role of Se in enhancing cotton growth and its efficiency in alleviating PEG-induced water stress and NaCl-induced salt stress under controlled conditions was conducted. The hydroponically grown cotton was supplied with selenium dioxide (SeO2) as a source of Se. The study included six treatments (control, 80 mM NaCl, 50 g/L PEG-6000, 10 µM Se, Se + NaCl and Se + PEG). All treatments were grown hydroponically in frequently aerated Hogland’s solution for 15 days. The experiment was repeated once again to validate the results. The results demonstrated that NaCl and PEG decreased cotton biomass, photosynthetic pigments and the essential macro-nutrients significantly. However, H2O2, OH˙ and MDA over-accumulated, CAT, POD and PPO activities up-regulated and SOD activity down-regulated by stress treatments. Plant biomass, pigments content and ionic balance were improved by Se supplementation to the growth medium. Nonetheless, ROS accumulation, Na uptake and the activities of CAT, POD and PPO were retrieved. The current work suggests Se as a potent treatment to counteract the detrimental effects of water and salt stresses on growth and metabolic activity of cotton.

Resistance to NaCl salinity is positively correlated with iron and zinc uptake potential of wheat genotypes

Context Soil salinity is a serious environmental issue that is drastically reducing crop productivity via limiting the uptake of important micronutrients including iron (Fe) and zinc (Zn). Aims To identify the wheat genotypes with better Fe and Zn uptake potential under saline conditions. Methods The seedlings of eight wheat genotypes (SARC-1, SARC-2, SARC-3, SARC-4, SARC-5, SARC-6, SARC-7 and SARC-8) were exposed to salinity (100 mM NaCl), deficiency of Fe and Zn (one-fourth of the control) and their combination of salinity and deficiency of Fe and Zn, created usingHoagland’s nutrient solution for 28 days. Key Results It was noticed that root and shoot growth of all the genotypes decreased due to salinity and nutrient (Fe and Zn) deficiency, and even higher in their combined treatment. The concentration of Na increased while K decreased under both salinity alone and it's combination with nutrient deficiency. The concentrations and uptake of Fe and Zn greatly decreased in the combinedapplication of salinity and nutrient deficiency followed by nutrient deficiency and saline treatments. Multivariate analysis showed that Na uptake was the major reason for the limited growth and nutrient uptake by wheat genotypes. Conclusions SARC-5 was the most sensitive genotype against salinity and nutrient deficiency. In contrast, SARC-1 was the most tolerant genotype against salinity, whichaccumulated the highest contents of both Fe and Zn. Among the eight genotypes used in the present study, SARC-1 is the most suitable genotype for cultivation on Zn and Fe deficient saline soils. Implications The obtained results would be very helpful for ensuring food security and quality in salt affected areas.

Role of Grafting in Tolerance to Salt Stress in Melon (Cucumis melo L.) Plants: Ion regulation and antioxidant defense systems

Grafting in vegetables is a method that has been commonly used in recent years, not just for the treatment of soil borne diseases and pests, but also to facilitate higher abiotic stress tolerance under conditions such as salinity. Herein, it was aimed to determine if the salt tolerance of two salt-susceptible melon genotypes, SCP-1 and SCP-2, could be improved by grafting onto TLR-1 and TLR-2, which are salt-tolerant melon genotypes, and Albatros commercial melon rootstock. The grafted plants were grown in plastic pots containing a peat: perlite mixture and exposed to NaCl at doses of 0 and 200 mM under greenhouse conditions. The salt-tolerant rootstock significantly diminished the damaging effects caused by salt stress via a reduction in the uptake of Na and Cl, which enhanced Ca and K uptake and micronutrition. Stress- induced activities of catalase, superoxide dismutase, ascorbate peroxidase, and glutathione reductase were considerably higher in the grafted plants. The results showed that grafting salt susceptible plants onto the salt-tolerant rootstock improved the growth regulation. The salt tolerance of the grafted melon seedlings may have partially been the result of the decreased Na and Cl, and malondialdehyde contents and higher antioxidant enzyme activities.

Sodium addition increases leaf herbivory and fungal damage across four grasslands

Abstract Sodium (Na) is an essential element for all animals, but not for plants. Soil Na supplies vary geographically. Animals that primarily consume plants thus have the potential to be Na limited and plants that uptake Na may be subject to higher rates of herbivory, but their high Na content also may attract beneficial partners such as pollinators and seed dispersers. To test for the effects of Na biogeochemistry on herbivory, we conducted distributed Na press experiments (monthly Na application across the growing season) in four North American grasslands. Na addition increased soil and plant Na concentrations at all sites. Grasses in Na addition plots had significantly higher herbivore damage by leaf miners and fungal pathogens than those in control plots. Forbs with higher foliar Na concentrations had significantly more chewing insect herbivore and fungal damage. While no pattern was evident across all species, several forb species had higher Na concentrations in inflorescences compared to leaves, suggesting they may allocate Na to attract beneficial partners. The uptake of Na by plants, and animal responses, has implications for the salinification in the Anthropocene. Increased use of road salt, irrigation with saline groundwater, rising sea levels and increasing temperatures and evapotranspiration rates with climate change can all increase inputs of Na into terrestrial ecosystems. Our results suggest increasing terrestrial Na availability will benefit insect herbivores and plant fungal pathogens. A free Plain Language Summary can be found within the Supporting Information of this article.

19 DIET-INDUCED OBESITY UNIQUELY REGULATES GLUCOSE AND NACL ABSORPTION IN SPRAGUE DAWLEY RAT SMALL INTESTINAL EPITHELIAL CELLS

Background Traditional coupled NaCl absorption occurs via the dual operation of Na:H (NHE3) and Cl:HCO3 (DRA/PAT1) exchange in the brush border membrane of villus cells in the mammalian small intestine. In genetic models of obesity (Zucker rat and Tallyho mouse) and humans, coupled NaCl absorption was not affected. However, in these animal models, a novel coupling of Na-glucose co-transport (SGLT1) and Cl:HCO3 exchange was increased, potentially important in the pathogenesis of diabetes and hypertension associated with obesity. Human obesity is both genetic and environmental (e.g. diet mediated). But it is not known whether this novel coupled NaCl absorptive pathway is affected in diet-induced obesity (DIO). Hypothesis Novel coupled NaCl absorption mediated by SGLT1 and DRA/PAT1 is stimulated in DIO. Aim Determine the mechanisms of regulation of SGLT1 and DRA/PAT1 in DIO. Methods Sprague Dawley rats were fed with a high-fat diet (HFD; 60% fat calories) from 12-18 wks of age to induce obesity. Control rats were fed with standard chow. BBM vesicles (BBMV) were prepared from villus cells by Mg precipitation. Phlorizine sensitive, 3H-OMG uptake for SGLT1; amiloride-sensitive, 22Na uptake for NHE3 and DIDS sensitive 36Cl uptake for Cl:HCO3 exchange was performed in villus cell BBMV. Na/KATPase activity was determined as inorganic phosphate release. Western blot studies were performed using rat specific antibodies. Results In intact rat villus cells, SGLT1 uptake was significantly increased in HFD rats (2.4±0.2 nmol/mg protein×2 min in control and 6.4±0.6 in HFD; n=4, p Conclusions In DIO, BBM SGLT1 activity was stimulated in villus cells from HFD rats. This is not due to the altered Na extruding capacity of the cell. Cl:HCO3 exchange was also stimulated in DIO while NHE3 remained unaffected. These data indicate that in DIO, while the traditional coupled NaCl absorption is unaffected, a novel coupled NaCl absorptive pathway, via SGLT1 and DRA/PAT1 is stimulated resulting in enhanced glucose and NaCl absorption which is likely important in the pathophysiology of diabetes and hypertension of obesity.

Cross‐linked polymers increase nutrient sorption in degraded soils

AbstractCross‐linked polymer hydrogels, polyacrylamide co‐polymer (XPAM) or polyacrylate (XPAA) offer potential solutions for soil degradation, declines in soil resilience, and poor productivity in marginal soils. However, little is known about their long‐term effect on soil nutrient availability. This 9‐yr, irrigated, outdoor, cropped pot study evaluated a single, one‐time addition of XPAM or XPAA at 0.25 or 0.5% dry wt. (5.6 or 11.2 Mg ha–1) in a degraded (artificially eroded) soil. Controls included an unamended degraded soil and an unamended, non‐degraded soil (i.e., topsoil). We measured nutrients in soil and leachate water each year, and in the first 5 yr, crop yields and nutrient uptake. Both hydrogels increased average soil pH and electrical conductivity (EC), soil extractable K, Na, and total organic carbon (TOC), and decreased soil extractable Mg relative to the control. Unlike XPAM, XPAA produced a greater increase in soil extractable K, increased extractable Fe, Zn, Mn, and Cu, increased Olsen P, and decreased total inorganic carbon (TIC). Neither hydrogel affected crop yields but XPAA increased K and Zn and decreased Mg and Na uptake in crops compared to controls. Relative to the control, both hydrogels decreased cumulative Ca, Mg, and S leaching mass losses and increased mean EC of leachate. Unlike XPAM, XPAA increased cumulative leaching mass losses of K, P, NO3–N, and NH4–N relative to the control. The hydrogels’ soil effects persisted for ≥7 yr, differing as a function of the quantity of included counterions and the stability of the gel structure after soil placement.

Continuous monitoring of plant sodium transport dynamics using clinical PET

BackgroundThe absorption, translocation, accumulation and excretion of substances are fundamental processes in all organisms including plants, and have been successfully studied using radiotracers labelled with 11C, 13N, 14C and 22Na since 1939. Sodium is one of the most damaging ions to the growth and productivity of crops. Due to the significance of understanding sodium transport in plants, a significant number of studies have been carried out to examine sodium influx, compartmentation, and efflux using 22Na- or 24Na-labeled salts. Notably, however, most of these studies employed destructive methods, which has limited our understanding of sodium flux and distribution characteristics in real time, in live plants. Positron emission tomography (PET) has been used successfully in medical research and diagnosis for decades. Due to its ability to visualise and assess physiological and metabolic function, PET imaging has also begun to be employed in plant research. Here, we report the use of a clinical PET scanner with a 22Na tracer to examine 22Na-influx dynamics in barley plants (Hordeum vulgare L. spp. Vulgare—cultivar Bass) under variable nutrient levels, alterations in the day/night light cycle, and the presence of sodium channel inhibitors.Results3D dynamic PET images of whole plants show readily visible 22Na translocation from roots to shoots in each examined plant, with rates influenced by both nutrient status and channel inhibition. PET images show that plants cultivated in low-nutrient media transport more 22Na than plants cultivated in high-nutrient media, and that 22Na uptake is suppressed in the presence of a cation-channel inhibitor. A distinct diurnal pattern of 22Na influx was discernible in curves displaying rates of change of relative radioactivity. Plants were found to absorb more 22Na during the light period, and anticipate the change in the light/dark cycle by adjusting the sodium influx rate downward in the dark period, an effect not previously described experimentally.ConclusionsWe demonstrate the utility of clinical PET/CT scanners for real-time monitoring of the temporal dynamics of sodium transport in plants. The effects of nutrient deprivation and of ion channel inhibition on sodium influx into barley plants are shown in two proof-of-concept experiments, along with the first-ever 3D-imaging of the light and dark sodium uptake cycles in plants. This method carries significant potential for plant biology research and, in particular, in the context of genetic and treatment effects on sodium acquisition and toxicity in plants.

Lignin-based hydrogel alleviates drought stress in maize

Global water shortage is a crisis for all living systems, including agricultural cropping systems. Water absorbent hydrogels from synthetic polymers can retain moisture from irrigation or rainfall and release it in response to crop water demands, but have a limited functional lifespan and may release byproducts that are harmful to plants or pollute the soil environment. Hydrogels fabricated from plant-based polymers are more suitable for agricultural cropping systems because they could improve the soil water availability to the crop and gradually biodegrade to harmless carbon dioxide and water. The objective of this work was to determine how biodegradable lignin hydrogel affected the soil water availability to maize grown under drought conditions. The lignin hydrogel was applied at 0.3 % and 0.6 % (by weight) in pots subjected to water deficit or sufficiency, and compared to sodium polyacrylate hydrogel that was applied at the same rates. Maize plants were taller, had greater phosphorus content and more biomass when grown in soil with lignin hydrogel and sodium polyacrylate hydrogel than without hydrogel. Furthermore, soil receiving 0.6 % lignin hydrogel produced significantly (P < 0.05) greater maize biomass and relative leaf water content, with an 86 % reduction in leaf proline content and 10 % less electrolyte leakage under severe drought conditions than without hydrogel. There was more soil soluble Na and Na uptake by maize in the sodium polyacrylate-amended soil due to solubilization of the Na+ ions from the sodium polyacrylate. We recommend lignin hydrogel as a soil additive to increase water availability to crops experiencing drought stress that will not release undesirable byproducts into the cropping system.