Potassium Absorption Research Articles

CRISPR/Cas9 Mediated Knockout of the OsbHLH024 Transcription Factor Improves Salt Stress Resistance in Rice (Oryza sativa L.).

Salinity stress is one of the most prominent abiotic stresses that negatively affect crop production. Transcription factors (TFs) are involved in the absorption, transport, or compartmentation of sodium (Na+) or potassium (K+) to resist salt stress. The basic helix–loop–helix (bHLH) is a TF gene family critical for plant growth and stress responses, including salinity. Herein, we used the CRISPR/Cas9 strategy to generate the gene editing mutant to investigate the role of OsbHLH024 in rice under salt stress. The A nucleotide base deletion was identified in the osbhlh024 mutant (A91). Exposure of the A91 under salt stress resulted in a significant increase in the shoot weight, the total chlorophyll content, and the chlorophyll fluorescence. Moreover, high antioxidant activities coincided with less reactive oxygen species (ROS) and stabilized levels of MDA in the A91. This better control of oxidative stress was accompanied by fewer Na+ but more K+, and a balanced level of Ca2+, Zn2+, and Mg2+ in the shoot and root of the A91, allowing it to withstand salt stress. Furthermore, the A91 also presented a significantly up-regulated expression of the ion transporter genes (OsHKT1;3, OsHAK7, and OsSOS1) in the shoot when exposed to salt stress. These findings imply that the OsbHLH024 might play the role of a negative regulator of salt stress, which will help to understand better the molecular basis of rice production improvement under salt stress.

Effects of the Powder from Hoggery Desulfurization Tanks on the Salinity Resistance of Lettuce.

Lettuce is an important vegetable cultivated worldwide, even in regions with highly saline soils. A large amount of research discusses the application of sulfur on the increase of antioxidation in plants. The powder from hoggery desulfurization tanks contained high amounts of sulfur and small amounts of other nutrients for plants. This powder can be added to liquid fertilizer to create high-sulfur liquid fertilizer (HSLF). This study observed the cell morphologies of lettuce root apices under salt stress after the application of HSLF. Lettuce plants were cultivated in hydroponic solutions containing one of two NaCl (0 and 40 mM) and three HSLF (0.0, 1.5, and 3.0 g L−1) concentrations. Salinity reduced the K+/Na+ ratio in the plant leaves; however, this reduction was smaller in the HSLF-treated plants. Except for phosphate and potassium, nutrient absorption is inhibited under conditions of high salinity. Using scanning electron microscopy, we observed apices more integrated on cell roots after increasing HSLF supplement under non-salt-stressed conditions. In addition, the cells were repaired after increasing the supplement of HSLF under the condition of 40 mM NaCl. Although salt stress reduced plant growth, the reductions were minimized in the HSLF-treated plants. The application of HSLF potentially alleviated salt injury in lettuce root apices and was probably associated with the improvement of phosphorus and potassium absorption and increasing K+/Na+ ratios in lettuce plants.

Expression of B. subtilis Phytase gene driven by fruit specific E8 promoter for enhanced minerals, metabolites and phytonutrient in cucumber fruit

The fruit nutrigenomics is an interesting and important research area towards nutrition enhancement. The phytic acid is one of the major antinutrient compound, present in seeded fruits and crops. It hinders the absorption of iron (Fe), zinc (Zn), magnesium (Mg), potassium (K) and calcium (Ca), causing mineral deficiencies. In the present study, the BsPhy gene was overexpressed in the cucumber fruits using the tomato fruit specific E8 and constitutive CaMV 35S promoter. The E8 promoter imparted heterologous expression of GUS gene in cucumber fruits, furthermore, the fruit specific expression of E8 promoter with BsPhy gene was confirmed in transgenics (E8::BsPhy) using anti rabbit-phytase antibody. The physio-biochemical analysis of transgenics revealed, maximum phytase activity in E8::BsPhy cucumber fruits at 10 days after anthesis (DAA) compared to 35S::BsPhy and wild-type (WT) fruits. Consequently, E8::BsPhy fruits also showed increased amount of inorganic phosphorus (Pi), total phosphorus (P), minerals (Zn, Fe, Mg, K, Ca), total carotenoid and other macronutrients at 10 DAA compared to 35S::BsPhy fruits. The metabolite profiling of fruits (10 DAA) showed increased sugars, amino acids, sugar acids and polyols, in both E8::BsPhy and 35S::BsPhy transgenics suggesting higher phytate metabolism, compared to WT fruits. Interestingly, both the transgenic fruits showed higher fruit biomass and yield along with improved nutritional quality, which can be attributed to increased P and Zn contents in transgenic fruits, compared to WT fruits. Our findings reveal that the BsPhy gene enhances minerals and macronutrients in transgenic cucumber fruits making it nutritious and healthy.

Spectral Diagnostic Model for Agricultural Robot System Based on Binary Wavelet Algorithm.

The application of agricultural robots can liberate labor. The improvement of robot sensing systems is the premise of making it work. At present, more research is being conducted on weeding and harvesting systems of field robot, but less research is being conducted on crop disease and insect pest perception, nutritional element diagnosis and precision fertilizer spraying systems. In this study, the effects of the nitrogen application rate on the absorption and accumulation of nitrogen, phosphorus and potassium in sweet maize were determined. Firstly, linear, parabolic, exponential and logarithmic diagnostic models of nitrogen, phosphorus and potassium contents were constructed by spectral characteristic variables. Secondly, the partial least squares regression and neural network nonlinear diagnosis model of nitrogen, phosphorus and potassium contents were constructed by the high-frequency wavelet sensitivity coefficient of binary wavelet decomposition. The results show that the neural network nonlinear diagnosis model of nitrogen, phosphorus and potassium content based on the high-frequency wavelet sensitivity coefficient of binary wavelet decomposition is better. The R2, MRE and NRMSE of nn of nitrogen, phosphorus and potassium were 0.974, 1.65% and 0.0198; 0.969, 9.02% and 0.1041; and 0.821, 2.16% and 0.0301, respectively. The model can provide growth monitoring for sweet corn and a perception model for the nutrient element perception system of an agricultural robot, while making preliminary preparations for the realization of intelligent and accurate field fertilization.

The ciliate protozoan Colpoda cucullus can improve maize growth by transporting soil phosphates

Little is known regarding the ability of protozoans to transfer phosphates and improve maize growth. The objective of this study was to determine whether Colpoda cucullus could improve the maize phosphorus (P) level by transferring phosphate. In this three-compartment root box study, the soil in the outer compartment was inoculated with the common ciliate, C. cucullus, together with the addition of either KH232PO4, rock phosphate (RP), super phosphate (SP) or ammonium phosphate (AP), and then maize was grown in the inner compartment. The results showed that the maize plants grown in the soil inoculated with C. cucullus had much higher 32P radioactivity than the control. Colpoda cucullus inoculation resulted in significant increases in dry matter by up to 25.07%, and nitrogen (N), P and potassium (K) absorption by 1–36% (P<0.05). Soil available P in the inner compartment of the root box was also enhanced by at least 30% due to the ciliate inoculation (P<0.05). It was therefore suggested that phosphates might be transported from the outer to inner compartments by the inoculated C. cucullus and then absorbed by the maize plant.

Homologous Cloning of Potassium Channel Genes From the Superior Apple Rootstock Line 12-2, Which is Tolerant to Apple Replant Disease.

Potassium channels are important ion channels that are responsible for the absorption of potassium in the plant nutrient uptake system. In this study, we used homologous molecular cloning to obtain 8 K+ channel genes from the superior apple rootstock line 12-2 (self-named): MsAKT1-1, MsKAT3-2, MsKAT1-3, MsK2P3-4, MsK2P3-5, MsK2P5-6, MsK2P3-7, and MsK2P3-8. Their lengths varied from 942 bp (MsK2P5-6) to 2625 bp (MsAKT1-1), and the number of encoded amino acids varied from 314 (MsK2P5-6) to 874 (MsAKT1-1). Subcellular localization predictions showed that MsAKT1-1, MsKAT3-2, and MsKAT1-3 were localized on the plasma membrane, and MsK2P3-4, MsK2P3-5, MsK2P5-6, MsK2P3-7, and MsK2P3-8 were localized on the vacuole and plasma membrane. The 8 K+ channel proteins contained α helices, extended strands, β turns, and random coils. MsKAT1-3 had four transmembrane structures, MsKAT3-2 had six, and the other six K+ channel genes had five. Protein structure domain analysis showed that MsAKT1-1 contained nine protein domains, followed by MsKAT3-2 with four, MsKAT1-3 with three, and the other five two-pore domain K+ channel proteins with two. Semi-quantitative RT-PCR detection of the K+ channel genes showed that their expression levels were high in roots. qRT-PCR analysis showed that the relative expression levels of the 8 genes changed after exposure to ARD stress. The above results provide a theoretical basis for further research on the functions of potassium channel genes in 12-2 and a scientific basis for the breeding of ARD-resistant rootstock.

Effects of Biodegradable Film Raw Material Particles on Soil Properties, Wheat Growth, and Nutrient Absorption and Transportation

Biodegradable plastic film is one of the effective ways to solve the problem of white pollution in agriculture. However, its impacts on soil-plant systems are not well documented. In order to provide a basis for the safety evaluation of large-scale application of biodegradable plastic film, pot experiments were conducted to investigate the effects of the types(H, S, and X) and doses(2.5, 10, and 40 g·kg-1) of biodegradable film raw material particles on the soil physiochemical properties, biological properties, growth, and nutrient absorption by wheat (Triticum aestivum L.). The results showed that three types of biodegradable film raw material particles significantly increased soil pH but had no significant effect on soil organic matter content; medium-high doses of H and low-medium doses of S plastic particles had a positive effect on soil nitrification and soil nitrogen availability, whereas X film particles had an inhibitory effect. H film particles increased soil available phosphorus content, and S and X had no significant effect. X film particles increased the content of soil available potassium, but S and H had no significant effect. The effects of three types of biodegradable raw material particles on soil enzyme activities varied with the types and doses of plastic film and enzyme types. With the increase in the doses of plastic film particles, the activities of three kinds of soil enzymes showed a downward trend. Except for the low and medium doses of the S treatment, the other treatments inhibited the growth of wheat, in which X film particles had the greatest inhibitory effect on the biomass of wheat roots, stems, leaves, and grain; with the increase in the doses of film particles, the inhibition effect of wheat biomass was more obvious. For wheat nutrients, the absorption of nitrogen was promoted at low doses and inhibited at high doses, and the three types of film particles inhibited the absorption of phosphorus and potassium. There were significant differences in the distribution ratio of nitrogen and phosphorus between the stems, leaves, and grains of wheat by all the film particles; however, there was no significant difference in the distribution ratio of potassium between those treatments. Correlation analysis showed that wheat biomass was the main factor affecting wheat nutrient accumulation.

Eplerenone–A novel Mineralocorticoid receptor antagonist for the clinical application

Aldosterone is produced from the zona glomerulosa of the adrenal cortex in the adrenal gland, which is main mineralocorticoid hormone. Upon binding the mineralocorticoid receptor, it regulates sodium and potassium absorption, secretion, and retention, thereby maintaining stable blood pressure levels. However, abnormal aldosterone synthesis and metabolism could be pathogenic and contribute to multiple organ fibrosis and structural remodeling. For instance, hyperaldosteronemia is critically involved in the development of hypertension, heart failure (HF), and renal disease. Therefore, mineralocorticoid receptor antagonists (MRAs) that could fight against high concentrations of aldosterone play an important role in the treatment of diseases caused by hyperaldosteronism. Eplerenone, as a novel selective MRA, has better therapeutic efficiency and fewer side effects comparing to the classical drug spironolactone. In this review, first, we go through the biosynthesis and biologic properties of aldosterone and then introduce how hyperaldosteronemia facilitates certain diseases progression. Aldosterone is an important part of the renin-angiotensin-aldosterone system (RAAS), which plays a crucial role in essential hypertension, atrial tremor, and tissue fibrosis. Second, we summarize current evidence of clinical application of eplerenone in the control of primary aldosteronism, hypertension, HF, nephropathy, insulin resistance, and liver damage. It is exciting that many studies have shown that the use of eplerenone in these diseases yields good outcomes accompanied with fewer adverse effects such as hyperkalemia, metabolic acidosis, hypotension, and acute kidney failure, which indicates that eplerenone is a strong and safe MRA and inhibitor of RAAS system. This review focuses on therapeutic efficacy and disadvantages of eplerenone when treating a series of different diseases. Ultimately, we hope to shed light on future therapeutic strategies in diseases associated with hyperaldosteronemia.

Effect of vapor pressure deficit on the photosynthesis, growth, and nutrient absorption of tomato seedlings

Vapor pressure deficit (VPD) is the main driving force of plant water transport and affects the nutrient absorption of plants. Exploring the nutrient absorption, growth, and photosynthetic characteristics of different tomato cultivars under different VPDs is of great importance for the cultivation of tomato. This experiment featured two levels of VPD (high 2.2/low 0.9 kPa) and two tomato cultivars (Solanumlycopersicum L., cv. Jinpeng and cv. Zhongza) for a total of four treatments in two controlled environment growth chambers. After about 4 weeks, the seedlings (at the three true-leaf stage) were transplanted into pots flled with inorganic medium and watered with nutrient solution. The stomatal characteristics, leaf moisture status, net photosynthetic rate (An), and plant growth of Jinpeng were not significantly different under the two VPD treatments, but high VPD resulted in a significantly increased transpiration rate (E) and whole plant hydraulic conductance (Kplant), as well as significantly increased absorption of potassium (K) and calcium (Ca) in various organs. In contrast, Zhongza had lower biomass, smaller stem height, and lower total leaf area under high vs. low VPD conditions. At high VPD, the reduction of photosynthesis in Zhongza was mainly caused by anatomical modifications of the stomata; significant reductions in stomatal aperture and length restricted photosynthesis and biomass accumulation. Moreover, the E and Kplant of Zhongza were reduced by stomatal state changes that prevent excessive transpiration. High VPD limited plant transpiration and mass flow of water, which reduced the absorption and accumulation of nutrients. Overall, these results suggest tomato cultivars differ in their stomatal sensitivity. Specifically, increasing VPD resulted in increased levels of some nutrients in certain organs in the cultivar with lower stomatal sensitivity; however, the cultivar with higher stomatal sensitivity demonstrated opposite trends.

Effect of Counterions on the Foliar Absorption and Transport of Potassium in Soybeans [Glycine max (L.) Merrill

Effect of Counterions on the Foliar Absorption and Transport of Potassium in Soybeans [<i>Glycine max</i> (L.) Merrill

Protein expression changes in response to potassium deficiency stress of industrial hemp plants using SWATH technology

Potassium availability in soil is one of the most important factors affecting the growth and metabolism of industrial hemp, having a major influence on plant growth and crop yield. SWATH proteomics was used to perform differential proteomics on rapidly-growing stems and leaves of a potassium-deficiency resistant (BM) and a potassium deficiency sensitive hemp variety (Y1), under potassium deficiency stress (0.2 mmol/L K+ in irrigation water). The differentially expressed proteins (DEPs) in BM and Y1 were identified through LC-ESI-MS/MS, finding 288 and 353 stem DEPs and 226 and 256 leaf DEPs, respectively. KEGG pathway analysis of the two varieties revealed that the DEPs in Y1 leaf, BM leaf, Y1 stem and BM stem were significantly enriched in 15, three, 11 and four pathways, respectively. Comparison and analysis of the DEPs, revealed that BM adapted to potassium deficiency stress through the following mechanisms: chlorophyll synthesis in both stem and leaf decreased and photosynthesis slowed; stem increased starch metabolism, oxidative stress resistance, lignin metabolism, cell membrane biosynthesis, cell division and ethylene biosynthesis; leaf regulated stomatal closure, enhanced photo-respiration and light energy transfer and activated protein anabolism. These findings provide important reference proteins and genetic information for future molecular study of the highly-efficient absorption of potassium by industrial hemp plants.

Root K Affinity Drivers and Photosynthetic Characteristics in Response to Low Potassium Stress in K High-Efficiency Vegetable Soybean.

Significant variations of potassium absorption and utilization exist in vegetable soybean. Pot and hydroponic experiments were carried out to examine the characteristics of root potassium (K) affinity-associated drivers and photosynthesis in vegetable soybean (edamame) [Glycine max (L.) Merr.] with different K efficiency. Two K high-efficiency vegetable soybean genotypes (Line 19 and Line 20) and two K low-efficiency genotypes (Line 7 and Line 36) were investigated in low K and normal K conditions. The root of K high-efficiency genotypes had a higher K+ affinity associated with a higher maximum K+ uptake rate (Imax), but lower Michaelis constant for K+ absorption (Km) and lower compensation concentration for K+ uptake (Cmin). Seedlings of K high-efficiency genotypes also had higher root vigor [triphenyl tetrazolium chloride (TTC) reduction method] and greater absorbing activity (methylene blue method), especially in the low K condition. Furthermore, the root bleeding-sap rate of K high-efficiency genotypes in low K stress was 9.9–24.3% greater than that of normal K conditions, which was accompanied by a relatively higher K concentration of root bleeding-sap in contributing to K+ upward flux. The root of K high-efficiency vegetable soybean genotypes exhibited K+ high-affinity and driving advantages. Photosynthetic parameters of K high-efficiency vegetable soybean genotypes were less affected by low K stress. Low K stress decreased the net photosynthetic rate of K high-efficiency genotypes by 6.1–6.9%, while that of K low-efficiency genotypes decreased by 10.9–15.7%. The higher chlorophyll (Chl) a/b ratio with enhanced relative content of Chl a in response to low K stress might be an adapted mechanism for K high-efficiency genotypes to maintain photosynthetic capacity. Stronger root K affinity drivers associated with photosynthetic adaptability to low K stress are the key factors in determining the K high-efficiency of vegetable soybeans.

Meta-analysis of the role of zinc in coordinating absorption of mineral elements in wheat seedlings

BackgroundZinc (Zn) is an important nutrient for human beings, which is also an essential micronutrient for crop growth. This study investigated the role of Zn in coordinating the mineral elements absorption in modern wheat (Triticum aestivum L.) cultivars with a new developed method.ResultsA method was developed, and showed a robust capability to simultaneously investigate seven mineral elements uptake in wheat seedling. With this method, we found low Zn supply (< 1 μM) promoted the absorption of potassium (K), magnesium (Mg) and manganese (Mn) in wheat seedling, while high Zn supply (> 1 μM) significantly inhibited the absorption of these elements. Cultivars with the green genes (Rht-B1b and Rht-D1b) showed a higher uptake capability on ammonium (NH4+), and cultivars with Rht-B1b allele can uptake more phosphors (P), K, calcium (Ca), Mn and Zn compared to cultivars with Rht-D1b. Further analysis indicated higher uptake capability of NH4+ in cultivars contained Rhts was independent of Zn.ConclusionThe key role of Zn in coordinating for mineral elements absorption was identified in modern wheat cultivars, providing the reference for Zn application in wheat. Meanwhile, this study provides a robust method for quantifying the absorption of mineral elements, which may be adopted into the broadly investigations on the coordinated nutrients absorption of plant.

Effect of the Matric Potential on Growth and Water, Nitrate and Potassium Absorption of Vegetables under Soilless Culture

To exploit the full potential of plants, it is essential to provide an adequate water balance during critical growth stages. With knowledge of the substrate’s matric potential, it is possible to realistically measure the amount of water available to the plant. The objective of this research is to study the effect of the matric potential of the substrate on the growth of beans, lettuce, sweet peppers, watermelon, and cauliflower plants. The research goal was to evaluate the effect of the matric potential on the main fertigation parameters of horticultural plants. The plants were cultivated at the University of Almería (Spain) in a controlled chamber in a pot with 250 mL of coconut fiber substrate from block propagation. For treatments T15, T30, T45, and T60, new irrigation was applied when easily available water (EAW) depletion levels of 15, 30, 45, and 60% were reached, respectively. The efficiency of the use of water (WUE), nitrate (NUE), and potassium (KUE) was measured. From T15 to T60, a significant effect was found for the absorption of water, nitrate and potassium, WUE, NUE, and KUE. T60 reduced the plant growth by half. The largest growth was between 15 and 30% of the level of use of EAW. Two different models were constructed according to each plant. It is possible to have a small depletion in the available water and still have plant growth, if there is a balance between the air and water needs of the substrate.

Ultracool Dwarfs Observed with the Spitzer Infrared Spectrograph. I. An Accurate Look at the L-to-T Transition at ∼300 Myr from Optical Through Mid-infrared Spectrophotometry

Abstract We present Spitzer IRS 5–14 μm spectra and 16 μm and 22 μm photometry of the T2.5 companion to the ∼300 Myr old G0V star HN Peg. We incorporate previous 0.8–5 μm observations to obtain the most comprehensive spectral energy distribution (SED) of an intermediate-gravity L/T-transition dwarf that, together with an accurate Gaia EDR3 parallax of the primary, enables us to derive precise fundamental parameters. We find that young (≈0.1–0.3 Gyr) early-T dwarfs on average have ≈140 K lower effective temperatures, ≈20% larger radii, and similar bolometric luminosities compared to ≳1 Gyr old field dwarfs with similar spectral types. Our accurate infrared spectrophotometry offers new detail at wavelengths where the dominant carbon-bearing molecules have their strongest transitions: at 3.4 μm for methane and at 4.6 μm for carbon monoxide. We assess the performance of various widely available photospheric models and find that models with condensates and/or clouds better reproduce the full SED of this moderately young early-T dwarf. However, cloud-free models incorporating a more general convective instability treatment reproduce at least the low-resolution near-infrared spectrum similarly well. Our analysis of R ≈ 2300 J-band spectra shows that the near-infrared potassium absorption lines in HN Peg B have similar strengths to those seen in both younger and older T2–T3 dwarfs. We conclude that while alkali lines are well established as surface gravity indicators for L-type or warmer stars, they are insensitive to surface gravity in early-T dwarfs.

Ground-based Transmission Spectroscopy with VLT FORS2: Evidence for Faculae and Clouds in the Optical Spectrum of the Warm Saturn WASP-110b

Abstract We present a ground-based optical transmission spectrum for the warm Saturn-mass exoplanet WASP-110b from two transit observations made with the FOcal Reducer and Spectrograph on the Very Large Telescope. The spectrum covers the wavelength range from 4000–8333 Å, which is binned in 46 transit depths measured to an averaged precision of 220 parts per million (ppm) over an averaged 80 Å bin for a Vmag = 12.8 star. The measured transit depths are unaffected by a dilution from a close A-type field dwarf, which was fully resolved. The overall main characteristic of the transmission spectrum is an increasing radius with wavelength and a lack of the theoretically predicted pressure-broadened sodium and potassium absorption features for a cloud-free atmosphere. We analyze archival high-resolution optical spectroscopy and find evidence for low to moderate activity of the host star, which we take into account in the atmospheric retrieval analysis. Using the AURA retrieval code, we find that the observed transmission spectrum can be best explained by a combination of unocculted stellar faculae and a cloud deck. Transmission spectra of cloud-free and hazy atmospheres are rejected at a high confidence. With a possible cloud deck at its terminator, WASP-110b joins the increasing population of irradiated hot-Jupiter exoplanets with cloudy atmospheres observed in transmission.

Arbuscular mycorrhizal fungi enhance the growth of the exotic speciesAmbrosia artemisiifolia

AbstractArbuscular mycorrhizal fungi (AMF) can increase host plant nutrient uptake via their mycelium, thus promoting plant growth. AMF have always been associated with successful invasion of most exotic plant species. However, knowledge regarding how AMF affect the success of plant invasion remains limited. Exotic Ambrosia artemisiifolia is an invasive and mycorrhizal plant species. A long-term field experiment was conducted to examine the differences in AMF diversity and composition in the roots of A. artemisiifolia and Setaria viridis subjected to interspecific competition during growth. A greenhouse experiment was also performed to test the effect of Funneliformis mosseae on the growth of these two species. Ambrosia artemisiifolia invasion caused AMF diversity to change in native S. viridis roots. Meanwhile, the relative abundance of F. mosseae was significantly higher in the roots of A. artemisiifolia than in those of S. viridis. The higher AMF colonization rate in the exotic species (A. artemisiifolia) than in the native species (S. viridis) was found in both the field and greenhouse experiments. The greenhouse experiment possibly provided that AMF advantaged to the growth of A. artemisiifolia, by influencing its photosynthetic capacity as well as its phosphorus and potassium absorption. These observations highlight the important relationship of AMF with the successful invasion of A. artemisiifolia.

Effect of ammonium nitrogen on pepper grown under soilless culture

The response of pepper (Capsicum annuum L.) to Ammonium-N was studied in a multispan greenhouse under soilless culture using coir fiber as substrate. Ammonium-N application rates were 0, 2, 4, 6 and 8 mM with a total-N concentration of 13 mM. The total content of the rest of all macronutrients in the nutrient solution was maintained from the beginning of the experiment until the end. The highest water uptake was recorded at 2 mM ammonium concentration in the nutrient solution. Compared to nitrate, ammonium nitrogen caused a decrease in nitrate absorption, but led to an increase when applying 8 mM ammonium. Despite a progressive increase in ammonium content in the nutrient solution, potassium absorption was constant below the ammonium concentration of 8 mM. Under a high N-NH4 content (from 6 to 8 mM) in the nutrient solution, high toxicity was found, deriving in the appearance of deformed or noncommercial fruits. There was a significant benefit by the use of ammonium as a component in the nutrient solution. The optimum yield ammonium concentrations were found in the range from 2 to 4 mM. Nevertheless, concentrations higher than 6 mM led into a decrease in commercial production, with the production of increasing deformed fruit, out of size and/or blossom-end rot.

Effects of Ridge Tillage and Straw Mulching on Cultivation the Fresh Faba Beans

Ridge tillage is an effective agronomic practice and a miniature precision agriculture; however, its effects on the growth of faba beans (Vicia faba L.) are poorly understood. This study aimed to determine the effect of ridge tillage and straw mulching on the root growth, nutrient accumulation and yield of faba beans. Field experiments were conducted during 2016 and 2017 cropping seasons and comprised four treatments: ridge tillage without any mulching (RT), flat tillage without any mulch (FT), flat tillage with rice straw mulched on the ridge tillage (FTRSM) and ridge tillage with rice straw mulched on the ridge tillage (RTRSM). The RT and RTRSM increased soil temperature and decreased soil humidity and improved soil total nitrogen, total phosphorus, available potassium and organic matter. RT and RTRSM increased the root length density, root surface area, root diameter and root activity of faba beans at flowering and harvest periods. The RT and RTRSM also increased the nitrogen, phosphorus, potassium absorption and the yield of faba beans. These results indicated that ridge tillage and straw mulching affect faba bean growth by improving soil moisture conditions and providing good air permeability and effective soil nutrition supply. This study provides a theoretical basis for the high yield cultivation improvement of faba beans.

The Potassium Transporter Hak1 in Candida Albicans, Regulation and Physiological Effects at Limiting Potassium and under Acidic Conditions.

The three families of yeast plasma membrane potassium influx transporters are represented in Candida albicans: Trk, Acu, and Hak proteins. Hak transporters work as K+-H+ symporters, and the genes coding for Hak proteins are transcriptionally activated under potassium limitation. This work shows that C. albicans mutant cells lacking CaHAK1 display a severe growth impairment at limiting potassium concentrations under acidic conditions. This is the consequence of a defective capacity to transport K+, as indicated by potassium absorption experiments and by the kinetics parameters of Rb+ (K+) transport. Moreover, hak1− cells are more sensitive to the toxic cation lithium. All these phenotypes became much less robust or even disappeared at alkaline growth conditions. Finally, transcriptional studies demonstrate that the hak1− mutant, in comparison with HAK1+ cells, activates the expression of the K+/Na+ ATPase coded by CaACU1 in the presence of Na+ or in the absence of K+.