Selenium hyperaccumulation by Astragalus (Fabaceae) does not inhibit root nodule symbiosis

• Premise of study: A survey of the root-nodule symbiosis in Astragalus and its interaction with selenium (Se) has not been conducted before. Such studies can provide insight into how edaphic conditions modify symbiotic interactions and influence partner coevolution. In this paper plant-organ Se concentration ([Se]) was investigated to assess potential Se exposure to endophytes. • Methods: Selenium distribution and molecular speciation of root nodules from Se-hyperaccumulators Astragalus bisulcatus, A. praelongus, and A. racemosus was determined by Se K-edge x-ray absorption spectroscopy. A series of greenhouse experiments were conducted to characterize the response of root-nodule symbiosis in Se-hyperaccumulators and nonhyperaccumulators. • Key results: Nodules in three Se-hyperaccumulators (Astragalus crotalariae, A. praelongus, and A. preussii) are reported for the first time. Leaves, flowers, and fruits from Se-hyperaccumulators were routinely above the hyperaccumulator threshold (1,000 µg Se g⁻¹ DW), but root samples rarely contained that amount, and nodules never exceeded 110 µg Se g⁻¹ DW. Nodules from A. bisulcatus, A. praelongus, and A. racemosus had Se throughout, with a majority stored in C-Se-C form. Finally, an evaluation of nodulation in Se-hyperaccumulators and nonhyperaccumulators indicated that there was no nodulation inhibition because of plant Se tolerance. Rather, we found that in Se-hyperaccumulators higher levels of Se treatment (up to 100 µM Se) corresponded with higher nodule counts, indicating a potential role for dinitrogen fixation in Se-hyperaccumulation. The effect was not found in nonhyperaccumulators. • Conclusions: As the evolution of Se hyperaccumulation in Astragalus developed, root-nodule symbiosis may have played an integral role.     

Effect of Organic Selenium Supplementation on Growth, Se Uptake, and Nutrient Utilization in Guinea Pigs

Forty weaned male guinea pigs (Cavia porcellus) of 152.6?±?7.96 g mean body weight were divided into four equal groups and fed a common basal diet comprised of 25% ground cowpea (Vigna unguiculata) hay, 30% ground maize (Zea mays) grain, 22% ground gram (Cicer arietinum) grain, 9.5% deoiled rice (Oryza sativa) bran, 6% soybean (Glycine max) meal, 6% fish meal, 1.5% mineral mixture (without Se), and ascorbic acid at 200 mg/kg to meet their nutrient requirements along with 0, 0.1, 0.2, and 0.3 ppm of organic selenium (Se) in groups I, II, III, and IV, respectively. Experimental feeding lasted for a period of 10 weeks, during which, daily feed intake and weekly body weights were recorded. Intake and digestibility of dry matter, organic matter, ether extract, crude fiber, and nitrogen-free extract as well as uptake of calcium and phosphorus were similar (P?>?0.05) among the four groups. Feed:gain ratio was also similar (P?>?0.05) in the four groups. However, digestibility of crude protein was significantly (P?<?0.001) higher in group II supplemented with 0.1 ppm organic Se as compared to other three group. Intake and absorption of Se was significantly (P?<?0.001) higher in all the Se supplemented groups as compared to control group. Average daily gain (ADG) was significantly (P?<?0.05) higher in group II (3.16 g/day) and III (3.38 g/day) as compared to group I (2.88 g/day). However, ADG in group IV (supplemented 0.3 ppm organic Se) was significantly (P?<?0.05) lower (2.83 g/day) than group II and III, but comparable (P?>?0.05) to group I. Findings of the present experiment suggests that Se requirements of guinea pigs are ≥0.2 ppm, as supplementation of 0.1 ppm organic Se in the diet (having 0.1 ppm Se) not only enhanced their growth rate but also improved the protein utilization.     

The Interactive Effect of Selenium and Farmyard Manure on Soil Microbial Activities,Yield and Selenium Accumulation by Wheat (Triticum aestivum L.) Grains

This study assessed the interactive effect of selenium (Se) and farmyard manure (FYM) on soil microbial activities, growth, yield, and Se accumulation by wheat grains. Preliminarily, the effect of Se (0–250 µg kg^?1 soil) and FYM (0–12.5 g kg^?1 soil) was assessed on soil microflora. Selenium exhibited an adverse impact on soil microflora; respiration was decreased at?≥?10 µg kg^?1 soil while dehydrogenase and urease activities were decreased at?≥?125 µg kg^?1 soil. At 250 µg Se kg^?1 soil, respiration, dehydrogenase and urease activities were decreased by 81, 40 and 35%, respectively, on unamended soil, and by 9, 47 and 22%, respectively, on FYM-amended soil. The subsequent plant experiments were conducted with same Se and FYM rates; one was harvested 42 days after sowing and other at crop maturity. The application of 125 µg Se kg^?1 and 12.5 g FYM kg^?1 soil improved seedling biomass by 12.6 and 22%, respectively, while their combined use lacked synergistic effect. Similarly, at maturity Se and FYM increased grain yield while their combined effect was not synergistic. The Se-induced suppression in microbial activities was not related to yield which was improved (11% at the highest rate in unamended soil) by Se application. Selenium application increased grain Se content in a rate-dependent manner, it increased from 0 to 1025 µg kg^?1 by applying 250 µg Se kg^?1 soil. Moreover, FYM application decreased Se accumulation in grains. It is concluded that FYM application increased soil microbial activities and yield but reduced grain Se accumulation in wheat on Se-applied soil.

     

Soil factors affecting selenium concentration in wheat grain and the fate and speciation of Se fertilisers applied to soil

UK crops have a low selenium (Se) status, therefore Se fertilisation of wheat (Triticum aestivum L.) at 10 field sites was investigated and the effect on the content and speciation of Se in soils determined. Soil characterisation was carried out at each field site to determine the soil factors that may influence wheat grain Se concentrations in unfertilised plots. Soil samples were taken after harvest from each treatment to determine the fate and speciation of selenate fertiliser applied to soil. Wheat grain Se concentrations could be predicted from soil Se concentration and soil extractable sulphur (S) using the following regression model: Grain Se?=?a?+?b(total soil Se)?+?c(extractable soil Se) - d(extractable soil S), with 86 % of the variance being accounted for, suggesting that these properties control Se concentrations in grain from unfertilised plots. Extractable soil Se concentrations were low (2.4 – 12.4 µg kg^?1) and predominantly consisted of selenite (up to 70 % of extractable Se) and soluble organic forms, whereas selenate was below the detection limit. Little of the added Se, in either liquid or granular form was left in the soil after crop harvest. Se fertilisation up to 20 g ha^?1 did not lead to a significant Se accumulation in the soil, suggesting losses of Se unutilised by the crop.     

Algal biomass production,N uptake and N2 fixation in a synthetic medium

An experiment was conducted in the growth chamber to quantify the biomass production, N removal and N₂ fixation from a synthetic medium by Chlamydomonas reinhardtii and Anabaena flos-aquae. Nitrogen was supplied at a concentration of 100 mg liter⁻¹ of NO₃⁻−¹⁵N and NH₄⁺−¹⁵ (3·5 atom %), respectively. After 21 days Chlamydomonas reinhardtii removed an average of 83·8 and 78·7 mg N liter⁻¹ as NO₃⁻ and NH₄⁺, respectively. Averages of 0·89 and 0·71 g liter⁻¹ (first batch), 1·63 and 0·95 g liter⁻ (second batch) algal biomass were collected from NO₃⁻ and NH₄⁺ media, respectively. Uptake rates of 0·11 mg ¹⁵N g⁻¹ algae day⁻¹ from NO₃⁻ medium and 0·10 mg ¹⁵N g⁻¹ algae day⁻¹ from NH₄⁺ medium were calculated. Algal cells grown in NO₃⁻ and NH₄⁺ medium contained 71 and 65 g N kg⁻¹ (first batch), 39 and 58 g N kg⁻¹ (second batch), respectively. Anabaena flos-aquae produced averages of 0·58 and 0·46 g liter⁻¹ (first batch), 0·55 and 0·48 g liter⁻¹ (second batch) after 14 days of growth from NO₃⁻ and NH₄⁺ media, respectively. Blue-green algal biomass contained higher N (81–98 g kg⁻¹) than green algae. Isotope dilution method for determining N₂ fixation indicated that 55% and 77% of total N of blue-green algae grown in NO₃⁻ and NH₄⁺ media, respectively, was derived from the atmosphere.     

In vivo Se binding to human plasma proteins after administration of SeO3

Binding of ^{7 5} Se to plasma proteins was studied in four cancer patients who received 200–250 μCi of ^{7 5} SeO₃²⁻ (1.25 μg of selenium) intravenously for tumor scans. During the hour after injection, the ^{7 5} Se disappeared rapidly from the plasma. Gel filtration chromatography and dialysis experiments indicated that a large amount of the ^{7 5} Se returned to the plasma bound to protein between 1 and 6 h after injection. Up to 16% of the plasma ^{7 5} Se was found in very-low-density lipoproteins and low-density lipoproteins as early as 3 mikn after injection but very little ^{7 5} Se was found in high density lipoproteins. The very low density lipoprotein ^{7 5} Se activity declined very rapidly whereas low density lipoprotein ^{7 5} Se activity fell more slowly. Zonal ultracentrifugal studies of one subject's lipoproteins revealed a continuum of ^{7 5} Se-binding proteins from the very low density lipoprotein peak to the low density lipoprotein peak. Most of the ^{7 5} Se could be removed from the lipoproteins by denaturation with 8 M urea or treatment with 0.5 M mercaptoethanol. These treatments removed very little of the ^{7 5} Se from plasma collected 48 h after injection indicating a different type of binding of selenium in lipoproteins than in other plasma proteins.     

Light and temperature mediate algal stimulation of heterotrophic activity on decomposing leaf litter

1. Recent evidence suggests that periphytic algae stimulate plant litter heterotrophs (fungi and bacteria) in the presence of light, but few studies have tested whether this stimulation varies across gradients of light, which may covary with temperature.
2. We exposed field-conditioned Typha domingensis litter to fully-crossed, short-term gradients of temperature (15, 20, 25, and 30°C) and light (0, 25, 53, 123, and 388 µmol quanta m⁻² s⁻¹) and measured responses of litter-associated algal, fungal, and bacterial production rates and β-glucosidase, β-xylosidase, and phenol oxidase enzyme activities in the laboratory.
3. Increased light stimulated algal production rates, from immeasurable production under darkness to >200 µg algal C g⁻¹ detrital C hr⁻¹ at the highest light level, with the greatest light sensitivity and maximal photosynthetic rates at 25°C. In turn, increased light stimulated fungal production rates, especially at the two highest temperatures and most strongly at 25°C where light stimulated fungal production by a mean of 65 µg C g⁻¹ detrital C hr⁻¹, indicating 2.1-fold stimulation by light. Bacterial production rates also responded to light, indicated by stimulation of a mean of 16 µg C g⁻¹ detrital C hr⁻¹ (1.6-fold) at 15°C, but stimulation was weaker at higher temperatures. Enzyme activities increased strongly with elevated temperature but were not affected by light.
4. Our experimental evidence suggests algae differentially stimulate litter-associated bacteria and fungi in a light-dependent manner that further depends on temperature. These findings advance understanding of the onset of algal stimulation of heterotrophy, including algal-induced priming effects during litter decomposition, in response to common covarying environmental gradients subject to global change.

     

Gypsum amendment to soil can reduce selenium uptake by alfalfa grown in the presence of coal fly ash

Experiments in the field and greenhouse were conducted in the presence of coal fly ash to determine whether gypsum can reduce Se concentration in alfalfa (Medicago sativa L.). In the field experiment, conducted at a coal fly ash landfill, 11.2 t ha^-1 gypsum was applied to soil as a top dressing to test the effect of gypsum in reducing selenium (Se) concentration in aboveground plant tissue. There were four treatment combinations of gypsum over a two year period, 1990 and 1991: (0, 0), (0, 11.2) (11.2, 0) and (11.2, 11.2). In 1991, the Se concentration was lower in alfalfa grown with gypsum regardless of whether the gypsum was applied in both years or in only one year, indicating that the effect of gypsum application in the first year persisted into the second year. Since there was no increase in aboveground biomass with added gypsum, differences in Se concentration reflect a competitive interaction between S and Se. In the greenhouse experiment, 12 soil treatments were tested: three levels of fly ash (0, 10 and 20%) in combination with each of four levels of gypsum (0, 2.5, 5, and 7.5%). The Se concentration in alfalfa grown in 10% fly ash declined linearly with increasing gypsum dose, resulting in a reduction in Se concentration of 0.04±0.02 μg g^-1 for each 1% gypsum added for the first harvest and 0.06±0.03 μg g^-1 for each 1% gypsum added in the second harvest. Based on these results, gypsum may prove useful as a management tool to reduce the uptake of Se by plants growing on coal fly ash landfills. ei]H Lambers     

Follicle-stimulating hormone stimulated differentiation and progesterone production of bovine granulosa cells in culture

Progesterone production of granulosa cells cultured in vitro is stimulated and cell differentiation increased, by follicle-stimulating hormone (FSH). This study examined whether the increased progesterone production observed when bovine granulosa cells are cultured occurs because (1) progesterone production by undifferentiated and/or differentiated cells is increased or (2) the differentiation of granulosa cells is stimulated. Viable bovine granulosa cells (2−3×10⁵) from follicles 5–8 mm in diameter were cultured in the presence of 0, 1, 10 and 100 μu FSH (1 μu ≡ 1 μg NIH-FSH-S1) for 6 days at 37°C in a humidified atmosphere of 5% CO₂ in air in 1 ml of a 1:1 mixture of Dulbecco's modified Eagle medium: Ham's F10 medium supplemented with 365 μg ml⁻¹ l-glutamine, 100 U ml⁻¹ penicillin and 100 μg ml⁻¹ streptomycin. Progesterone production, total DNA and protein, and cell diameter were determined sequentially over the culture period. The increases in progesterone production (ng μg⁻¹ DNA per 24 h), cytoplasmic:nuclear ratio (μg protein μg⁻¹ DNA) and cell diameter (μm) over 6 days culture indicated that granulosa cells underwent differentiation in the presence of FSH. Progesterone production of undifferentiated granulosa cells (diameter 14 μm or less) was stimulated by FSH (P < 0.01) in a dose dependent manner (1.0±0.2, 2.9±0.3, 3.7±0.3 and 4.9±0.4 ng μg⁻¹ DNA per 24 h for 0, 1, 10 and 100 μu ml⁻¹ FSH respectively) but remained constant within dose (P > 0.05) during a 6 day culture period. FSH stimulated (P < 0.05) the rate of granulosa cell differentiation (10±3%, 53±13%, 74±21% and 82±10% differentiating cells per well for 0 μu, 1 μu, 10 μu and 100 μu ml⁻¹ FSH respectively) but did not stimulate (P > 0.05) progesterone production by differentiating granulosa cells (8.7±0.5 ng μg⁻¹ DNA per 24 h). In conclusion, the increase in progesterone production of FSH-stimulated granulosa cells cultured in vitro appears to be mainly due to an increase in the number of differentiating cells with a constant rather than an increasing progesterone production per cell.     

In vivo 7 5 Se binding to human plasma proteins after administration of 7 5 SeO32−

Binding of ^{7 5} Se to plasma proteins was studied in four cancer patients who received 200–250 μCi of ^{7 5} SeO₃^2? (1.25 μg of selenium) intravenously for tumor scans. During the hour after injection, the ^{7 5} Se disappeared rapidly from the plasma. Gel filtration chromatography and dialysis experiments indicated that a large amount of the ^{7 5} Se returned to the plasma bound to protein between 1 and 6 h after injection. Up to 16% of the plasma ^{7 5} Se was found in very-low-density lipoproteins and low-density lipoproteins as early as 3 mikn after injection but very little ^{7 5} Se was found in high density lipoproteins. The very low density lipoprotein ^{7 5} Se activity declined very rapidly whereas low density lipoprotein ^{7 5} Se activity fell more slowly. Zonal ultracentrifugal studies of one subject's lipoproteins revealed a continuum of ^{7 5} Se-binding proteins from the very low density lipoprotein peak to the low density lipoprotein peak. Most of the ^{7 5} Se could be removed from the lipoproteins by denaturation with 8 M urea or treatment with 0.5 M mercaptoethanol. These treatments removed very little of the ^{7 5} Se from plasma collected 48 h after injection indicating a different type of binding of selenium in lipoproteins than in other plasma proteins.     

A Flexible Porous Carbon Nanofibers‐Selenium Cathode with Superior Electrochemical Performance for Both Li‐Se and Na‐Se Batteries

A flexible and free‐standing porous carbon nanofibers/selenium composite electrode (Se@PCNFs) is prepared by infiltrating Se into mesoporous carbon nanofibers (PCNFs). The porous carbon with optimized mesopores for accommodating Se can synergistically suppress the active material dissolution and provide mechanical stability needed for the film. The Se@PCNFs electrode exhibits exceptional electrochemical performance for both Li‐ion and Na‐ion storage. In the case of Li‐ion storage, it delivers a reversible capacity of 516 mAh g^?1 after 900 cycles without any capacity loss at 0.5 A g^?1. Se@PCNFs still delivers a reversible capacity of 306 mAh g^?1 at 4 A g^?1. While being used in Na‐Se batteries, the composite electrode maintains a reversible capacity of 520 mAh g^?1 after 80 cycles at 0.05 A g^?1 and a rate capability of 230 mAh g^?1 at 1 A g^?1. The high capacity, good cyclability, and rate capability are attributed to synergistic effects of the uniform distribution of Se in PCNFs and the 3D interconnected PCNFs framework, which could alleviate the shuttle reaction of polyselenides intermediates during cycling and maintain the perfect electrical conductivity throughout the electrode. By rational and delicate design, this type of self‐supported electrodes may hold great promise for the development of Li‐Se and Na‐Se batteries with high power and energy densities.     

Variation in seedling growth of 11 perennial legumes in response to phosphorus supply

Phosphorus (P) deficiency is a major problem for Australian agriculture. Development of new perennial pasture legumes that acquire or use P more efficiently than the current major perennial pasture legume, lucerne (Medicago sativa L.), is urgent. A glasshouse experiment compared the response of ten perennial herbaceous legume species to a series of P supplies ranging from 0 to 384 µg g^?1 soil, with lucerne as the control. Under low-P conditions, several legumes produced more biomass than lucerne. Four species (Lotononis bainesii Baker, Kennedia prorepens F.Muell, K. prostrata R.Br, Bituminaria bituminosa (L.) C.H.Stirt) achieved maximum growth at 12 µg P g^?1 soil, while other species required 24 µg P g^?1. In most tested legumes, biomass production was reduced when P supply was ≥192 µg g^?1, due to P toxicity, while L. bainesii and K. prorepens showed reduced biomass when P was ≥24 µg g^?1 and K. prostrata at ≥48 µg P g^?1 soil. B. bituminosa and Glycine canescens F.J.Herm required less soil P to achieve 0.5 g dry mass than the other species did. Lucerne performed poorly with low P supply and our results suggest that some novel perennial legumes may perform better on low-P soils.     

Mercury and Selenium in Stranded Indo-Pacific Humpback Dolphins and Implications for Their Trophic Transfer in Food Chains

As top predators in the Pearl River Estuary (PRE) of China, Indo-Pacific humpback dolphins (Sousa chinensis) are bioindicators for examining regional trends of environmental contaminants in the PRE. We examined samples from stranded S. chinensis in the PRE, collected since 2004, to study the distribution and fate of total mercury (THg), methylmercury (MeHg) and selenium (Se) in the major tissues, in individuals at different ages and their prey fishes from the PRE. This study also investigated the potential protective effects of Se against the toxicities of accumulated THg. Dolphin livers contained the highest concentrations of THg (32.34±58.98 µg g⁻¹ dw) and Se (15.16±3.66 µg g⁻¹ dw), which were significantly different from those found in kidneys and muscles, whereas the highest residue of MeHg (1.02±1.11 µg g⁻¹ dw) was found in dolphin muscles. Concentrations of both THg and MeHg in the liver, kidney and muscle of dolphins showed a significantly positive correlation with age. The biomagnification factors (BMFs) of inorganic mercury (Hg_inorg) in dolphin livers (350×) and MeHg in muscles (18.7×) through the prey fishes were the highest among all three dolphin tissues, whereas the BMFs of Se were much lower in all dolphin tissues. The lower proportion of MeHg in THg and higher Se/THg ratios in tissues were demonstrated. Our studies suggested that S. chinensis might have the potential to detoxify Hg via the demethylation of MeHg and the formation of tiemannite (HgSe) in the liver and kidney. The lower threshold of hepatic THg concentrations for the equimolar accumulation of Se and Hg in S. chinensis suggests that this species has a greater sensitivity to THg concentrations than is found in striped dolphins and Dall’s porpoises.     

Enrichment of laccase production by Phoma herbarum isolate KU4 under solid-state fermentation by optimizing RSM coefficients using genetic algorithm

The process parameters were optimized to obtain enhanced enzyme activity from the fungus Phoma herbarum isolate KU4 using rice straw and saw dust as substrate under solid-state fermentation using Response surface methodology (RSM). Genetic algorithm was used to validate the RSM for maximum laccase production. Six variables, viz., pH of the media, initial moisture content, copper sulphate concentration, concentration of tannic acid, inoculum concentration and incubation time were found to be effective and optimized for enhanced production. Maximum laccase production was achieved by RSM at pH 5·0 and 86% of initial moisture content of the culture medium, 150 µmol l⁻¹ of CuSO₄, 1·5% tannic acid and 0·128 g inoculum g⁻¹ dry substrate inoculum size on the fourth day of fermentation. The highest laccase activity was observed as 79 008 U g⁻¹, which is approximately sixfold enhanced production compared to the unoptimized condition (12 085·26 U g⁻¹).     

Continuous ethanol production by yeast immobilized on to channeled alumina beads

Vertical and near-horizontal (15° angle) packed-bed columns were compared for continuous ethanol fermentation using an alcohol- and glucose-tolerant Saccharomyces cerevisiae strain immobilized on to channeled alumina beads (5·0 × 10⁹ cells g⁻¹ beads). Spaces between beads (1·0–6·5 mm) and angle (15°) of near-horizontal reactor columns (with six ports in each) efficiently removed CO₂ and increased ethanol productivity. Malt-glucose-yeast-extract broth containing 16·7% glucose at 35°C fed at a dilution rate of 3· h⁻¹ to thw two horizontal columns (in series) yielded maximum ethanol productivity of 40·0 g liter⁻¹ h⁻¹. Feedstock flow rate and other factors (temperature, pH, nutrients, and glucose levels) affected productivities. The immobilized-cell system showed operational stability for >3 months without plugging, and could be stored for at least one year with no loss of bioreactor performance. Scanning electron micrographs of the beads revealed large numbers of yeast-cells attached on to internal and external surfaces of beads.     

The effect of dietary inclusion of starch,sucrose and xylose on the utilization of dietary energy in sheep

A calorimetric experiment of 4 × 4 Latin square design was undertaken to study the effect of sugar-beet pulp (SBP), maize starch, sucrose and xylose on energy metabolism in sheep. The four diets comprised a diet (A) of dried grass, soya-bean meal and SBP (450, 50 and 500 g kg⁻¹ on dry matter (DM) basis) and corresponding diets in which 400 g kg⁻¹ of SBP was replaced by maize starch (B), sucrose (C) or xylose (D); all diets were offered at a level of 600 g DM day⁻¹. After the Latin square was completed, energy value of the basal diet of dried grass and soya-bean meal (900 and 100 g kg⁻¹ DM; 600 g day⁻¹) was determined in the same four sheep.Treatment differences in organic matter, gross energy, nitrogen (N) and neutral detergent fibre (NDF) digestibility were non-significant. Differences in N retention were not significant.Digestible energy (DE) contents (MJ kg⁻¹ DM) were 13.27, 13.22, 13.21 and 13.21 MJ kg⁻¹ for diets A, B, C and D, respectively. Energy loss in methane was higher (P < 0.05) for Diet A than for other diets. Metabolizable energy (ME) contents for the diets A-D were 11.25, 11.22, 11.32 and 11.40 MJ kg⁻¹ DM, respectively. Metabolizability (q) of the diets averaged 0.642 and was not significantly affected by the diet given. There was a trend for heat production to be higher in sheep given the sucrose-containing diet (C) than in those given other diets (6.34 versus 6.04 MJ day⁻¹) and as a result, energy retention was lower (0.38 versus 0.64 MJ day⁻¹), but the difference did not reach statistical difference. Efficiencies of utilization of ME for maintenance and fattening (k_mf) averaged 0.67 and were in good agreement with those predicted from equations of the Agricultural Research Council (1980) excepting the lower k_mf (0.63) for Diet C.The mean ME content of SBP calculated by difference was 13.05 MJ kg⁻¹ DM and the corresponding values for mixtures of SBP + starch, SBP + sucrose and SBP + xylose (600 and 400 g kg⁻¹ DM) were 12.98, 13.16 and 13.36 MJ kg⁻¹ DM, respectively.     

High synergistic antibacterial,antibiofilm, antidiabetic and antimetabolic activity of Withania somnifera leaf extract-assisted zinc oxide nanoparticle

Nanotechnology is currently gaining immense attention to combat food borne bacteria, and biofilm. Diabetes is a common metabolic disease affecting majority of people. A better therapy relies on phytomediated nanoparticle synthesis. In this study, W. somnifera leaf extract-assisted ZnO NPs (Ws-ZnO NPs) was synthesized and characterized. From HR-TEM analysis, it has been found that the hexagonal wurtzite particle is 15.6 nm in size and − 12.14 mV of zeta potential. A greater antibacterial effect of Ws-ZnO NPs was noticed against E. faecalis and S. aureus at 100 µg mL⁻¹. Also, the biofilm of E. faecalis and S. aureus was greatly inhibited at 100 µg mL⁻¹ compared to E. coli and P. aeruginosa. The activity of α-amylase and α-glucosidase enzyme was inhibited at 100 µg mL⁻¹ demonstrating its antidiabetic potential. The larval and pupal development was delayed at 25 µg mL⁻¹ of Ws-ZnO NPs. A complete mortality (100%) was recorded at 25 µg mL⁻¹. Ws-ZnO NPs showed least LC₅₀ value (9.65 µg mL⁻¹) compared to the uncoated ZnO NPs (38.8 µg mL⁻¹) and leaf extract (13.06 µg mL⁻¹). Therefore, it is concluded that Ws-ZnO NPs are promising to be used as effective antimicrobials, antidiabetic and insecticides to combat storage pests.

     

Relation between algal available phosphate in the sediments of the River Garonne and chemically-determined phosphate fractions

Concentrations of total and inorganic phosphate were measured in forty-seven sediments of the River Garonne (France) using an anion resin, NaOH 0.1 M, Ca-NTA and Na-EDTA. Algal available P was measured using Scenedesmus crassus. The sediments presented a wide range of Tot-P concentrations (226 to 923 μg g⁻¹). Resin P varied between 1.1 to 55.5 μg g⁻¹ and NaOH-P between 3.5 to 262 μg g⁻¹. NTA-P and EDTA-P varied between 13.9 and 178 μg g⁻¹ and between 14.4 to 261 μg g⁻¹ respectively. Algal available P varied between 8.8 to 262 μg g⁻¹/ All forms of P are highly correlated and specially with algal available P (r = 0.70, 0.77, 0.88 and 0.77 for resin-P, NaOH-P, NTA-P and EDTA-P respectively). Nevertheless the partial correlation between EDTA-P and algal available P dropped to 0.05 when the concentration of NTA-P was considered as constant, indicating a spurious correlation with apatitic phosphate (extracted by Na-EDTA). Because of the strongest R ² and the lowest standard error of estimate, phosphate extracted by Ca-NTA can be considered as the best predictor of algal available phosphate.     

Application of sodium selenate to cowpea (Vigna unguiculata L.) increases shoot and grain Se partitioning with strong genotypic interactions

BackgorundCowpea is a crop widely used in developing countries due its rusticity. Besides its rich genotypic variability, most breeding programs do not explore its potential to improve elements uptake. Selenium (Se) is a scarce element in most soils, resulting in its deficiency being common in human diets. This study aimed to evaluate the interaction between biofortification with Se and genotypic variation in cowpea, on the concentrations of Se in roots, leaves + stem and grains.MethodsTwenty-nine cowpea genotypes were grown in a greenhouse in the absence (control) and presence of Se (12.5 μg Se kg⁻¹ soil) as sodium selenate, in fully randomized scheme. The plants were cultivated until grains harvest. The following variables were determined: roots dry weight (g), leaves + stems dry weight (g), grains dry weight (g), Se concentration (mg kg⁻¹) in roots, leaves + stems and grains, and Se partitioning to shoots and grains.ResultsSelenium application increased the Se concentration in roots, leaves + stems and grains in all genotypes. At least twofold variation in grain Se concentration was observed among genotypes. Selenium application did not impair biomass accumulation, including grain dry weight. Genotype “BRS Guariba” had the largest Se concentration in grains and leaves + stems. Genotype MNC04-795 F-158 had the largest partitioning of Se to shoots and grain, due to elevated dry weights of leaves + stems and grain, and high Se concentrations in these tissues.ConclusionThis information might be valuable in future breeding programs to select for genotypes with better abilities to accumulate Se in grain to reduce widespread human Se undernutrition.