Potassium Translocation Research Articles

NP and 9311 are excellent population parents for screening QTLs of potassium-efficient rice.

High and stable rice yields are critical to global food security, and potassium-deficient soils in East Asia have seriously limited rice production in the regions. It is feasible to screen potassium efficient quantitative trait locus(QTLs) from existing rice varieties to cope with rice production in potassium-deficient areas, and the selection of population parents is the key to locating major QTLs. After a long period of natural selection, potassium efficient rice varieties mainly exist in the region where the soil potassium level is low. The present study chose the representative twelve high-yielding rice varieties in east Asia, firstly, to measure plant height, fresh sheath weight, and fresh blade weight under hydroponic conditions. Based on the difference and consistency of the three parameters, NP as low potassium tolerant, and 9311 as low potassium sensitive rice variety were screened. We further analyzed the relative values of the six parameters of NP and 9311 treated with a culture medium containing different potassium (K+) concentrations and showed that the two varieties significantly differed in multiple low potassium concentrations. Meanwhile, we calculated the coefficient of variation of twelve rice varieties and most of those parameters reached a maximum at 4 mg/L K+, indicating that this concentration was suitable for screening potassium-efficient rice. We also measured the potassium content and the potassium-related traits in NP and 9311 tissues, and found that NP and 9311 significantly differed in potassium translocation. These differences may be responsible for the long-distance transport of potassium from the root to the aboveground part. In conclusion, we identified a pair of parents with significant differences in potassium translocation, which can be used to locate the relevant QTLs with high potassium efficiency to cope with the crisis of soil potassium deficiency in East Asia.

Co-application of ACC deaminase-producing rhizobial bacteria and melatonin improves salt tolerance in common bean (Phaseolus vulgaris L.) through ion homeostasis

A comprehensive body of scientific evidence indicates that rhizobial bacteria and melatonin enhance salt tolerance of crop plants. The overall goal of this research was to evaluate the ability of Rhizobium leguminoserum bv phaseoli to suppress salinity stress impacts in common bean treated with melatonin. Treatments included bacterial inoculations (inoculated (RI) and non-inoculated (NI)), different salinity levels (non-saline (NS), 4 (S1) and 8 (S2) dS m−1 of NaCl) and priming (dry (PD), melatonin (PM100) and hydro (PH) priming) with six replications in growing media containing sterile sand and perlite (1:1). The results showed that the bacterial strain had the ability to produce indole acetic acid (IAA), ACC deaminase and siderophore. Plants exposed to salinity stress indicated a significant decline in growth, yield, yield components, nitrogen fixation and selective transport (ST), while showed a significant increase in sodium uptake. However, the combination of PM100 and RI treatments by improving growth, photosynthesis rate and nitrogen fixation positively influenced plant performance in saline conditions. The combined treatment declined the negative impacts of salinity by improving the potassium translocation, potassium to sodium ratio in the shoot and root and ST. In conclusion, the combination of melatonin and ACC deaminase producing rhizobium mitigated the negative effects of salinity. This result is attributed to the increased ST and decreased sodium uptake, which significantly reduced the accumulation of sodium ions in shoot.

Salinity Tolerance Characteristics of Marginally Located Rice Varieties in the Northernmost Rice-Growing Area in Europe

Detailed experiments were performed to investigate the effects of the marginal cultivation of temperate japonica rice on salinity tolerance in different developmental stages and to detect new genetic resources for further research and breeding projects. Eight rice varieties were screened for salinity tolerance in a greenhouse at two developmental stages. During seedling-stage screening, stress was induced with a 12 dS m−1 NaCl solution. For reproductive-stage analysis, we applied continuous salinity stress (8.39 dS m−1 of soil extract at 25 °C (EC25)). We compared the marginal rice genotypes (japonica_1) to widely grown controls (those being Mediterranean japonica genotypes, referred as the japonica_2 group, which also included one indica genotype). Without stress, marginally cultivated genotypes had significantly higher potassium storage capacity (406 µmol g−1) in flag leaves than did japonica_2 (347) or indica (267). Moreover, the seeds contained twice as much sodium (5.27) as did the others (2.19 and 2.00). Based on root-to-grain allocation, we identified two sodium excluders (‘Dular’ and ‘Dáma’) and six includers under constant salinity stress. Among the includers, we found that ‘M488’ had extremely high sodium concentration in both the flag leaves (250.54 µmol g−1) and the grains (13.57 µmol g−1). Rice varieties bred for the edge of their habitat show special physiological patterns. The differences are mainly manifested as lower levels of antioxidant pigments, higher amounts of potassium in flag leaves, and higher sodium levels in grains under normal conditions. With the onset of stress, higher tillering ability, enhanced antioxidant pigment synthesis, and rapid potassium translocation from the root are the key mechanisms which help the plants to avoid serious damage caused by salinity.

Salt-Tolerant Compatible Microbial Inoculants Modulate Physio-Biochemical Responses Enhance Plant Growth, Zn Biofortification and Yield of Wheat Grown in Saline-Sodic Soil.

A wide range of root-associated mutualistic microorganisms have been successfully applied and documented in the past for growth promotion, biofertilization, biofortification and biotic and abiotic stress amelioration in major crops. These microorganisms include nitrogen fixers, nutrient mobilizers, bio-remediators and bio-control agents. The present study aimed to demonstrate the impact of salt-tolerant compatible microbial inoculants on plant growth; Zn biofortification and yield of wheat (Triticum aestivum L.) crops grown in saline-sodic soil and insight of the mechanisms involved therein are being shared through this paper. Field experiments were conducted to evaluate the effects of Trichoderma harzianum UBSTH-501 and Bacillus amyloliquefaciens B-16 on wheat grown in saline-sodic soil at Research Farm, ICAR-Indian Institute of Seed Sciences, Kushmaur, India. The population of rhizosphere-associated microorganisms changed dramatically upon inoculation of the test microbes in the wheat rhizosphere. The co-inoculation induced a significant accumulation of proline and total soluble sugar in wheat at 30, 60, 90 and 120 days after sowing as compared to the uninoculated control. Upon quantitative estimation of organic solutes and antioxidant enzymes, these were found to have increased significantly in co-inoculated plants under salt-stressed conditions. The application of microbial inoculants enhanced the salt tolerance level significantly in wheat plants grown in saline-sodic soil. A significant increase in the uptake and translocation of potassium (K+) and calcium (Ca2+) was observed in wheat co-inoculated with the microbial inoculants, while a significant reduction in sodium (Na+) content was recorded in plants treated with both the bio-agents when compared with the respective uninoculated control plants. Results clearly indicated that significantly higher expression of TaHKT-1 and TaNHX1 in the roots enhances salt tolerance effectively by maintaining the Na+/K+ balance in the plant tissue. It was also observed that co-inoculation of the test inoculants increased the expression of ZIP transporters (2–3.5-folds) which ultimately led to increased biofortification of Zn in wheat grown in saline-sodic soil. Results suggested that co-inoculation of T. harzianum UBSTH-501 and B. amyloliquefaciens B-16 not only increased plant growth but also improved total grain yield along with a reduction in seedling mortality in the early stages of crop growth. In general, the present investigation demonstrated the feasibility of using salt-tolerant rhizosphere microbes for plant growth promotion and provides insights into plant-microbe interactions to ameliorate salt stress and increase Zn bio-fortification in wheat.

Radioisotope 7Be, 210Pb, 137Cs and 40K in the needles of larch and cedar in the Novy Urengoy region (Arctic part of Western Siberia)

Annual needles of larch and cedar were sampled in the tundra zone of the Arctic part of Western Siberia in order to determine 7Be, 210Pb, 137Cs and 40K specific activities. Higher concentrations of 137Cs and 40K in the needles of cedar relative to the needles of larch can be associated with a clear difference in the properties of accumulation and translocation of cesium and potassium among these species. Higher concentrations of 7Be and 210Pb in the needles of larch relative to cedar needles and close isotopic ratios (7Be/210Pb) are probably due to more efficient aerosol deposition on vegetative canopies of larch.

Expression Patterns of Genes Encoding Sugar and Potassium Transport Proteins Are Simultaneously Upregulated or Downregulated When Carbon and Potassium Availability Is Modified in Shiraz (Vitis vinifera L.) Berries.

A link between the accumulation of sugar and potassium has previously been described for ripening grape berries. The functional basis of this link has, as of yet, not been elucidated but could potentially be associated with the integral role that potassium has in phloem transport. An experiment was conducted on Shiraz grapevines in a controlled environment. The accumulation of berry sugar was curtailed by reducing the leaf photoassimilation rate, and the availability of potassium was increased through soil fertilization. The study characterizes the relationship between the accumulation of sugar and potassium into the grape berry and describes how their accumulation patterns are related to the expression patterns of their transporter proteins. A strong connection was observed between the accumulation of sugar and potassium in the grape berry pericarp, irrespective of the treatment. The relative expression of proteins associated with sugar and potassium transport across the tonoplast and plasma membrane was closely correlated, suggesting transcriptional coregulation leading to the simultaneous translocation and storage of potassium and sugar in the grape berry cell.

Zinc oxide nanoparticles alleviate drought-induced alterations in sorghum performance, nutrient acquisition, and grain fortification

Drought is a major environmental event affecting crop productivity and nutritional quality, and potentially, human nutrition. This study evaluated drought effects on performance and nutrient acquisition and distribution in sorghum; and whether ZnO nanoparticles (ZnO-NPs) might alleviate such effects. Soil was amended with ZnO-NPs at 1, 3, and 5 mg Zn/kg, and drought was imposed 4 weeks after seed germination by maintaining the soil at 40% of field moisture capacity. Flag leaf and grain head emergence were delayed 6–17 days by drought, but the delays were reduced to 4–5 days by ZnO-NPs. Drought significantly (p < 0.05) reduced (76%) grain yield; however, ZnO-NP amendment under drought improved grain (22–183%) yield. Drought inhibited grain nitrogen (N) translocation (57%) and total (root, shoot and grain) N acquisition (22%). However, ZnO-NPs (5 mg/kg) improved (84%) grain N translocation relative to the drought control and restored total N levels to the non-drought condition. Shoot uptake of phosphorus (P) was promoted (39%) by drought, while grain P translocation was inhibited (63%); however, ZnO-NPs lowered total P acquisition under drought by 11–23%. Drought impeded shoot uptake (45%), grain translocation (71%) and total acquisition (41%) of potassium (K). ZnO-NP amendment (5 mg/kg) to drought-affected plants improved total K acquisition (16–30%) and grain K (123%), relative to the drought control. Drought lowered (32%) average grain Zn concentration; however, ZnO-NP amendments improved (94%) grain Zn under drought. This study represents the first evidence of mitigation of drought stress in full-term plants solely by exposure to ZnO-NPs in soil. The ability of ZnO-NPs to accelerate plant development, promote yield, fortify edible grains with critically essential nutrients such as Zn, and improve N acquisition under drought stress has strong implications for increasing cropping systems resilience, sustaining human/animal food/feed and nutrition security, and reducing nutrient losses and environmental pollution associated with N-fertilizers.

Polyaspartic acid mediates the absorption and translocation of mineral elements in tomato seedlings under combined copper and cadmium stress

Polyaspartic acid (PASP) is a nontoxic, biodegradable, environmentally friendly polymer and is widely used as a fertilizer synergist in agricultural production. In many old orchards and vegetable gardens, highly fertile soil is often accompanied by severe heavy metal contamination. The present study was designed to investigate mineral element interactions mediated by PASP under copper (Cu)+cadmium (Cd) combined stress to provide reasonable suggestions for scientific fertilization. A pot experiment was conducted in which tomato seedlings served as plant materials. A concentration of 700 mg L−1 PASP and foliar spraying application methods were selected based on previous experiments. Four treatments were applied: normal soil (control (CK)), Cu+Cd (combined stress), Cu+Cd+PASP, and normal soil+PASP. The plant biomass, root activity, and mineral elements were measured, and these data were analyzed by Data Processing System (DPS) statistical software. The results showed that, under Cu+Cd combined stress, PASP promoted stem diameter growth, root activity and chlorophyll content and ultimately increased the biomass of tomato seedlings to different degrees. Moreover, the content of both Cu and Cd and their individual accumulation in plants decreased. PASP increased the distribution of Cu and Cd in the roots under Cu+Cd combined stress, and the translocation ability from the roots to shoots was significantly restricted. With respect to essential elements, PASP promoted mainly the absorption and translocation of potassium (K), calcium (Ca), and magnesium (Mg), which greatly exerted physiological roles. However, the variation trends of Cu and Cd under normal soil conditions contrasted with those under stress conditions. With respect to essential elements other than K, Ca, and Mg, PASP mostly restrained their absorption but promoted their translocation. The regulatory mechanism of PASP differed between the combined stress conditions and normal soil conditions. Under the combined stress conditions, PASP seemed to mainly promote these advantageous factors that exert physiological regulatory functions. Under normal soil conditions, PASP mainly acted as a biological stimulant or signaling molecule for increased nutrient efficiency, which caused greater biomass productivity.

Effect of potassium on uptake and translocation of sodium and potassium in Chinese cabbage under NaCl stress

To investigate the influence of potassium (K+) on the salinity tolerance of Chinese cabbage (Brassica pekinensis Rupr.) seedlings, the plants were cultured at three K+ levels (0, 5, or 10 mM), under normal (0 mM NaCl) and high-salt (100 mM NaCl) conditions. The results indicated that the dry weight of Chinese cabbage increased with the application of K+ under salt stress. Addition of K+ increased K+ concentrations and suppressed sodium (Na+) concentration, which eventually increased the K+/Na+ ratios in roots or shoots. Application of K+ enhanced the uptake of K+ and suppressed the uptake of Na+. Moreover, the ratios of shoot-K+/root-K+ increased considerably, but the ratios of shoot-Na+/root-Na+ decreased in response to K+ application. It was concluded that the application of K+ could enhance the salt stress tolerance in Chinese cabbage because more K+ than Na+ was absorbed and translocated from roots to shoots.

Potassium translocation combined with specific root uptake is responsible for the high potassium efficiency in vegetable soybean

Uptake of potassium (K) in crops depends mainly on the root system. Field, pot and hydroponic experiments were carried out to characterise root morphological traits and examine their roles in K uptake and utilisation of vegetable soybean (edamame) (Glycine max (L.) Merr.). Of 40 genotypes, two high K-efficiency (HKE) and two low K-efficiency (LKE) genotypes were identified and compared at two levels of K application: nil or 120 kg K2SO4 ha–1. HKE genotypes had shorter total root length and smaller root surface area and root volume than LKE genotypes, but responded earlier to low-K conditions by adjusting root architecture. In plants receiving nil K, total root length was increased by 10.4–21.8% for HKE genotypes but decreased by 5.5–9.5% for LKE genotypes at the V4 stage relative to plants receiving applied K. HKE genotypes were more efficient in redistributing K from source to sink tissue, especially from leaf. Of the total K in vegetative tissues, 35.0–46.4% was redistributed to seed in HKE genotypes, whereas only 19.7–28.2% was redistributed in LKE genotypes. HKE genotypes also had a higher specific K uptake rate (K uptake per unit root length), 1.6–1.7 times higher than LKE genotypes at the R5 stage. This indirectly indicated a stronger root K acquisition in HKE genotypes. This study suggests that future vegetable soybean improvement with greater K efficiency should be focused on the selection of higher K-redistribution rate and specific K-uptake rate.

Effect of manganese stress on the mineral content of the leaves of wheat seedlings by use of X-ray fluorescence excited by synchrotron radiation

The present study describes the potential of the synchrotron radiation based X-ray fluorescence spectroscopy technique for the rapid, sensitive, user friendly and simultaneous monitoring of the changes in the elemental profile of the wheat seedlings stressed by excess manganese (Mn). For this, X-ray fluorescence spectra of the leaves of the control and Mn treated wheat seedlings have been recorded by synchrotron radiation X-ray of energy 15 keV. The analyses of the recorded spectra show the presence of elements chlorine, potassium, calcium, manganese, iron, copper, nickel, and zinc. A calibration-free approach, PyMca has been used for the quantitative estimation of the detected elements in the leaves of the control and Mn treated wheat seedlings. The excess supply of Mn to wheat seedlings results in the accumulation of manganese in the leaves of the seedlings. The accumulation of manganese in wheat seedlings negatively affects the uptake and translocation of calcium, potassium, and iron while it has stimulating effect on the uptake of copper and zinc.

Translocation of Potassium in Initiating Reset of Monoamine Transporter Proteins from Microsecond Molecular Dynamics Simulations

Our intent is to characterize the complete transport mechanism of the serotonin transporter (SERT) computationally, employing both a single bilayer and dual bilayer system to investigate this phenomenon. The work presented here represents the data collected from our most recent dual bilayer system from 178,044 atom simulations after 1 µs of simulation time. Herein, we utilize the human SERT protein crystal structure (PDB 5I6X), embedded in POPE lipid membrane. Ions were added to either side of the membrane at physiological concentrations, maintaining the membrane potential at −67 mV, representative of resting potential. Potential was determined using the Goldman-Hodgkin-Katz equation. Systems were run on both XSEDE and Pittsburgh Supercomputing Center resources. After 1 µs molecular dynamics simulations using the CHARMM force field, we observe translocation of potassium to the central substrate binding site in both SERT and the dopamine transporter (DAT). In both cases, potassium is interacting with a conserved aspartic acid residue in the pocket (D98 in SERT and D79 in DAT). The translocation of potassium to the central binding pocket after 1 µs supports experimental data that suggests potassium is necessary for reset of SERT. Simulations are currently running to characterize the complete transport mechanism. A more complete understanding of the transport process can aid in drug discovery and design for treatments of disorders associated with these proteins, such as depression and related disorders.

Seasonal Uptake of Nutrients by Chenin Blanc in Sand Culture: II. Phosphorus, Potassium, Calcium and Magnesium

The seasonal uptake of phosphorus, potassium, calcium and magnesium as well as their distribution in the vine were determined for Chenin blanc/99R vines grown in sand culture under South African climatic conditions. Phosphorus absorption showed two distinct peaks-the first ranging from after bud burst until veraison, and the second, less prominent, from about five weeks after harvest into the leaf fall period. Potassium was absorbed from about three weeks after bud burst until four to five weeks after harvest. No potassium was absorbed during leaf fall. Active absorption of calcium started after bud burst and continued until veraison. A second, less pronounced absorption period occurred during the six weeks before leaf fall. Similarly, absorption of magnesium started after bud burst and continued until veraison, after which the absorption rate decreased and ceased with the onset of leaf fall. A significant amount of the phosphorus and potassium absorbed during the post harvest period was retained in the permanent parts of the vine. However, most of the post harvest calcium and magnesium gains were lost through leaf fall. Most of the calcium retained by the permanent parts of the vine, was stored in the bark. There was an apparent translocation of potassium from the leaves to the permanent structure of the vine during leaf fall. This was not noticeable for any of the other three nutrients.

Effects of Fertilizer Levels on the Absorption, Translocation, and Distribution of Phosphorus and Potassium in Rice Cultivars with Different Nitrogen-Use Efficiencies

&lt;p&gt;The fertilizer management and the selection of rice cultivars play a vital role in rice production to maximize yield and minimize fertilizer cost. Many researches have elucidated the combined increase of nitrogen (N) accumulation and N use efficiency (NUE) in different rice genotypes, however, the accumulation, translocation, distribution of phosphorus (P) and potassium (K), and the correlation of N, P and K absorption characteristics and their relationships with grain yield in rice cultivars with different NUE is still obscure. For this purpose, two rice cultivars differing in NUE were chosen for this study, one with high-NUE (Dexiang 4103) and the other with low-NUE (Yixiang 3724). Fertilizers were applied at three levels, including low (75 kg N·hm&lt;sup&gt;-2&lt;/sup&gt;, 37.5 kg P&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt;·hm&lt;sup&gt;-2&lt;/sup&gt;, 75 kg K&lt;sub&gt;2&lt;/sub&gt;O·hm&lt;sup&gt;-2&lt;/sup&gt;), medium (150 kg N·hm&lt;sup&gt;-2&lt;/sup&gt;, 75 kg P&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt;·hm&lt;sup&gt;-2&lt;/sup&gt;, 150 kg K&lt;sub&gt;2&lt;/sub&gt;O·hm&lt;sup&gt;-2&lt;/sup&gt;), high rate (225 kg N·hm&lt;sup&gt;-2&lt;/sup&gt;, 112.5 kg P&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt;·hm&lt;sup&gt;-2&lt;/sup&gt;, 225 kg K&lt;sub&gt;2&lt;/sub&gt;O·hm&lt;sup&gt;-2&lt;/sup&gt;). A no-N treatment was included for each level as the control. The results showed that there were obvious interacting effects of cultivars and fertilizer levels on grain yield, as well as the absorption and translocation of P and K. Rice cultivars exhibited markedly stronger effects on total spikelets and the translocation of P and K in leaves, compared to fertilizer levels. The opposite trend was observed for grain yield, P and K accumulation at the main growth stages, and P and K translocation in stem and leaf sheaths. Compared with other treatments, the combined application of NPK fertilizers at medium level promoted nutrient accumulation, increased the nutrient harvest index, facilitated nutrient translocation in vegetative organs, and ultimately improved grain yield in both cultivars. The equilibrium relationship between N, P and K accumulation and grain yield indicated that the grain yield associated with high-NUE cultivar could reach more than 10,000 kg hm&lt;sup&gt;-2&lt;/sup&gt;, with N, P, and K requirements of 180.8-213.3, 47.3-54.7, and 223.5-259.1 kg hm&lt;sup&gt;-2&lt;/sup&gt;, respectively. Additionally, the correlation analysis revealed that accumulation and translocation of P, K during different growth stages was significantly (P &amp;lt; 0.05) related to grain yield and nutrient accumulation in different NUE cultivars. This study suggested that varieties with high-NUE also has high P and K use efficiencies, indicating that the conventional screening of varieties with high P or K use efficiencies can be included in the selection of high-NUE varieties. The increase of P and K accumulation and translocation during the period from heading to maturity was helpful to maintain a high-yield and NUE in rice production.&lt;/p&gt;

Biometric analysis of arabica coffee grown in low potassium nutrient solution under greenhouse conditions

Genetic parameters and associations between morpho-agronomic traits and nutritional efficiencies of arabica coffee cultivars were estimated to identify promising traits to assist in the selection of coffee genotypes efficient in potassium use, under limiting conditions of this nutrient. The experiment was conducted in a greenhouse with 20 arabica coffee cultivars grown in nutrient solution with a low potassium level (1.5 mM), using a randomized block design with three replicates. The traits evaluated were plant height, number of leaves, number of nodes, internode length, stem diameter, leaf area, rooting efficiency, potassium absorption efficiency, potassium translocation efficiency, biomass production efficiency, and potassium use efficiency. Genetic variability among coffee cultivars for all the evaluated traits was found. The phenotypic variance for all traits showed a higher contribution of genetic variance compared to environmental variance. Plant height, internode length, stem diameter, leaf area, biomass production efficiency, and potassium use efficiency had a genotypic determination coefficient (H2) above 80% and variation index greater than one. Leaf area and stem diameter had significant and positive genetic correlations with rooting, biomass production, and potassium use efficiencies. Stem diameter has great potential for use in breeding programs with a goal of indirect selection of cultivars that have greater potassium use efficiency in environments with restrictions of this nutrient.

Nitrate-Dependent Control of Shoot K Homeostasis by the Nitrate Transporter1/Peptide Transporter Family Member NPF7.3/NRT1.5 and the Stelar K+ Outward Rectifier SKOR in Arabidopsis.

Root-to-shoot translocation and shoot homeostasis of potassium (K) determine nutrient balance, growth, and stress tolerance of vascular plants. To maintain the cation-anion balance, xylem loading of K(+) in the roots relies on the concomitant loading of counteranions, like nitrate (NO3 (-)). However, the coregulation of these loading steps is unclear. Here, we show that the bidirectional, low-affinity Nitrate Transporter1 (NRT1)/Peptide Transporter (PTR) family member NPF7.3/NRT1.5 is important for the NO3 (-)-dependent K(+) translocation in Arabidopsis (Arabidopsis thaliana). Lack of NPF7.3/NRT1.5 resulted in K deficiency in shoots under low NO3 (-) nutrition, whereas the root elemental composition was unchanged. Gene expression data corroborated K deficiency in the nrt1.5-5 shoot, whereas the root responded with a differential expression of genes involved in cation-anion balance. A grafting experiment confirmed that the presence of NPF7.3/NRT1.5 in the root is a prerequisite for proper root-to-shoot translocation of K(+) under low NO3 (-) supply. Because the depolarization-activated Stelar K(+) Outward Rectifier (SKOR) has previously been described as a major contributor for root-to-shoot translocation of K(+) in Arabidopsis, we addressed the hypothesis that NPF7.3/NRT1.5-mediated NO3 (-) translocation might affect xylem loading and root-to-shoot K(+) translocation through SKOR. Indeed, growth of nrt1.5-5 and skor-2 single and double mutants under different K/NO3 (-) regimes revealed that both proteins contribute to K(+) translocation from root to shoot. SKOR activity dominates under high NO3 (-) and low K(+) supply, whereas NPF7.3/NRT1.5 is required under low NO3 (-) availability. This study unravels nutritional conditions as a critical factor for the joint activity of SKOR and NPF7.3/NRT1.5 for shoot K homeostasis.

Sulfate influx transporters in Arabidopsis thaliana are not involved in arsenate uptake but critical for tissue nutrient status and arsenate tolerance

Arsenic, a non-nutrient metalloid is toxic to plants but many details on the physiology of plant adaptation to arsenic stress are not well understood. This work provides new insights about the role of sulfur assimilation in arsenate uptake, growth and arsenic tolerance. Research reported here indicates that two high affinity sulfate transporters in Arabidopsis thaliana are not involved in root uptake of arsenate. Further this study revealed that sulfate status influenced thiol levels, elemental nutrients, growth and arsenate tolerance. The hypothesis that arsenate may be transported via sulfate transporters, SULTR1;1 and SULTR1;2 in Arabidopsis, was tested. The double mutant of sultr1;1 sultr1;2 exhibited significantly less growth than the wild-type or the single mutants. The double mutant's sulfur content was significantly lower than the wild-type but the single mutants were similar to the wild-type confirming the redundant functions of SULTR1;1 and SULTR1;2. Gene expression analyses indicated that the double mutant's sulfate uptake could be explained by the expressions of SULTR1;3, SULTR2;1, and SULTR2;2 in its roots. Following arsenate supply to the roots, the double mutant accumulated significantly less arsenic in the roots and the shoots than did the single mutants and the wild-type. The double mutant accumulated significantly less potassium and phosphorus also. (35)S sulfate supplied to wild-type or double mutant roots showed that sulfate uptake was not inhibited by arsenate. Taken together, these results indicate that root uptake of arsenate is probably not via sulfate transporters, but the poor growth of the double mutant of sultr1;1 and sultr1;2 was due to its poor sulfate status and decreased levels of thiols, which had pleiotropic effects on the root uptake and translocation of potassium and phosphorus and arsenic tolerance.

Mineralogical and chemical variability of mountain red/brown Mediterranean soils

The purpose of the current study was to quantitatively explore the dynamics of clay pedogenesis in red-brown soils of the terra-rossa type and associated soils (mainly Rhodoxeralfs) of the Mediterranean region with respect to bedrock and dust composition, and the impact of the vegetation-translocated elements silicon and potassium. Fifteen non-cultivated, shallow and leached mountain pedons were sampled in Israel along three transects that represent various rainfall ranges and bedrock lithologies. Bulk and clay fraction chemical and mineralogical compositions, as well as grain size, were determined. Quantitative relative analysis of clay minerals displayed a large variability that was largely affected by leaching. Leaching was dependent on rainfall amount and bedrock/soil permeability. In general, if the better soils were drained and leached the higher were the amounts of both kaolinite and illitic phases. Soil clay assemblages lay between two mineralogical end members: one with dominance of smectite and the second with high values of kaolinite and illitization parameters. Potassium and silicon were mobile in soils relative to aluminum, but under high rainfall or certain vegetation, translocation by vegetation reached a degree that promoted illite or smectite formation. Local combinations of rainfall, bedrock/soil permeability, and vegetation translocation of potassium and silicon dictated a large variability in clays, including illite formation, within a restricted group of red-brown Mediterranean soils.

Potassium nutrition of ectomycorrhizal Pinus pinaster: overexpression of the Hebeloma cylindrosporum HcTrk1 transporter affects the translocation of both K+ and phosphorus in the host plant

Mycorrhizal associations are known to improve the hydro-mineral nutrition of their host plants. However, the importance of mycorrhizal symbiosis for plant potassium nutrition has so far been poorly studied. We therefore investigated the impact of the ectomycorrhizal fungus Hebeloma cylindrosporum on the potassium nutrition of Pinus pinaster and examined the involvement of the fungal potassium transporter HcTrk1. HcTrk1 transcripts and proteins were localized in ectomycorrhizas using in situ hybridization and EGFP translational fusion constructs. Importantly, an overexpression strategy was performed on a H.cylindrosporum endogenous gene in order to dissect the role of this transporter. The potassium nutrition of mycorrhizal pine plants was significantly improved under potassium-limiting conditions. Fungal strains overexpressing HcTrk1 reduced the translocation of potassium and phosphorus from the roots to the shoots of inoculated plants in mycorrhizal experiments. Furthermore, expression of HcTrk1 and the phosphate transporter HcPT1.1 were reciprocally linked to the external inorganic phosphate and potassium availability. The development of these approaches provides a deeper insight into the role of ectomycorrhizal symbiosis on host plant K(+) nutrition and in particular, the K(+) transporter HcTrk1. The work augments our knowledge of the link between potassium and phosphorus nutrition via the mycorrhizal pathway.

A time dependent behavior of radiocesium from the Fukushima-fallout in litterfalls of Japanese flowering cherry trees

Radiocesium (134Cs + 137Cs) concentrations, primarily derived from the Fukushima accident in March 2011, were measured in litterfalls and green leaves of Japanese flowering cherry trees (Prunus x yedoensis cv. Somei-Yoshino). The sampling was performed mainly during the defoliation season in 2011 and 2012 using traps to collect litterfalls before contact with the ground. The average radiocesium concentration in litterfalls in 2012 fell to one-third of that in 2011 (0.43 and 1.2 kBq kg-DW−1, respectively). Interestingly, the concentrations in litterfalls collected in late autumn in both 2011 and 2012 (0.68 and 0.19 kBq kg-DW−1, respectively) were significantly lower than those in litterfalls collected in the early autumn (1.7 and 1.1 kBq kg-DW−1, respectively). In addition, the reductions in radiocesium concentrations in the litterfall were nearly synchronous with those in potassium concentrations (p ≤ 0.05). On the contrary, radiocesium concentrations in green leaves were also correlated with potassium concentrations; however, the slopes of the regression lines between the radiocesium and potassium concentrations were very similar in the 2011 litterfalls and the 2012 litterfalls, while the slopes were significantly different between these litterfalls and the green leaves. Consequently, the correlation between potassium and radiocesium was clear but independently observable in each of the litterfalls and the green leaves. It is possible that the reduction in radiocesium concentration occurred as a part of physiological demand, a translocation of potassium from the leaves to the body/twigs.