Room temperature solvent extraction for simple and fast determination of total concentration of Ca,Cu, Fe,Mg, Mn,and Zn in bee pollen by FAAS along with assessment of the bioaccessible fraction of these elements using in vitro gastrointestinal digestion

Background and aimBee pollen is recognized to be a source of different nutrients, including minerals. As a food supplement, its quality and safety due to concentrations of essential macro- and microelements, and harmful trace elements has to be verified. Fast and simple element analysis of bee-collected pollen can be regarded as an important part of its quality assurance and control. The present study aimed at developping a new method for determination of selected elements (Ca, Cu, Fe, Mg, Mn, Zn) of bee pollen based on solvent extraction and completely avoiding a high temperature treatment with concentrated reagents. In addition, in vitro gastrointestinal digestion was used to assess bioavailability of elements from this food supplement.MethodsBee pollen samples were dried and pulverized. Total concentrations of Ca, Cu, Fe, Mg, Mn, and Zn were determined by flame atomic absorption spectrometry (FAAS) in sample solutions obtained by wet digestion (WD) in concentrated HNO₃ or alternatively by solvent extraction (SE) with diluted solutions of HNO₃. Gastrointestinal digestion was mimicked using simulated solutions of gastric and intestinal juices followed by determination of Ca, Cu, Fe, Mg, Mn and Zn concentrations in the bioaccessible fraction by FAAS.ResultsA new simple and fast method for determination of total concentrations of Ca, Cu, Fe, Mg, Mn, and Zn in bee pollen was developed and validated. The method combined room temperature, two-hour SE with 0.5 mol L⁻¹ HNO₃ with FAAS measurements versus simple standard solutions. It provided precision within 1–5 % and trueness better than 8%, and was shown to be suitable for fast analysis of different polyfloral bee pollens. In vitro gastrointestinal digestion revealed that elements were well (70–85 % for Ca, Mg) and fairly (27–43 % for Cu, Fe, Mn, and Zn) bioaccessible from bee pollen. By pouring with water and swelling overnight, bioaccessibility of studied elements from such prepared bee pollen was increased on average by less than 15 % (Mn), 20 % (Ca, Cu, Fe, Zn) or 30 % (Mn).ConclusionsAvoiding long-lasting, high-temperature wet digestion with concentrated reagents, the proposed sample treatment along with FAAS provided precise and true results of total concentrations of Ca, Cu, Fe, Mg, Mn, and Zn in bee pollen. The method was simple and fast, and enabled to analyze a higher number of samples. Simulated gastrointestinal digestion of bee pollen have shown for the first time that Ca and Mg are the most bioaccessible from this bee product. Bioaccessibility of Cu, Fe, Mg, and Zn from bee pollen are close to or lower than 40 %.     

The use of growth and ingestion rates of Capitella sp. I as the bioassay approaches to determine the sediment quality of coastal wetlands of Taiwan

Food is a limiting factor for the deposit feeders. The availability of sediment nutrients thus has a tight relationship with the growth, survival and development of the animal. There are two purposes of this study: (1) to determine if the ingestion and growth rates can be used as a bioassay approach to assess the sediment nutrients; and (2) use the combination of bioassay approaches and chemical analyses to determine which chemical parameter is the better predicator of the sediment nutrients to the animals. In the preliminary study, the optimal growth length and average ingestion rate of Capitella sp. I were obtained from the laboratory. The standardized relationships of the growth and ingestion rates in response to different nutrients were prepared. Then, the sediments collected from different coastal wetlands in Western Taiwan were used in the feeding, growth experiments and chemical analyses. The comparisons were made between the field and laboratory experiments to determine the sediment nutrients in the wetland of Taiwan. In the growth rate standardized relationship, Capitella sp. I increased its growth rate with the total organic nitrogen (TON) concentration between 0 to 2.8 mgN·g sediment⁻¹, total organic carbon (TOC) concentration between 0 and 22.4 mgC·g sediment⁻¹, and enzymatically hydrolyzable amino acid (EHAA) concentration between 0 and 4.48 mg protein·g sediment⁻¹. After the nutrient concentrations exceed these values, the growth rates decreased gradually. In the ingestion rate standardized relationship, the animal increased its ingestion rate with the total organic nitrogen (TON) concentration between 0 and 2 mgN·g sediment⁻¹, total organic carbon (TOC) concentration between 0 and 14.1 mgC·g sediment⁻¹, and EHAA concentration between 0 and 3.2 mg protein·g sediment⁻¹. After the nutrient concentrations exceed these values, the ingestion rates also decreased. To determine which nutrient parameter is the best predictor for the sediment nutrient in the field, we first analyzed whether the data obtained from the laboratory fell within 99% confidence interval of the regression obtained from the field data. Then, to determine which parameter had the shortest perpendicular distance between the field and the laboratory regression curves. Both the growth and ingestion rates comparisons showed that the EHAA is the best candidate of the sediment nutrient of deposit feeders in the field. The results of this study proved tentatively that the growth and ingestion rates of Capitella sp. I can be used as the bioassay approaches to estimate the sediment nutrients. The combination of the bioassay approaches and the relevant chemical analyses allows us to determine the bioavailability fraction of sediment to the deposit feeders.     

Subcellular Nutrient Element Localization and Enrichment in Ecto- and Arbuscular Mycorrhizas of Field-Grown Beech and Ash Trees Indicate Functional Differences

Mycorrhizas are the chief organ for plant mineral nutrient acquisition. In temperate, mixed forests, ash roots (Fraxinus excelsior) are colonized by arbuscular mycorrhizal fungi (AM) and beech roots (Fagus sylvatica) by ectomycorrhizal fungi (EcM). Knowledge on the functions of different mycorrhizal species that coexist in the same environment is scarce. The concentrations of nutrient elements in plant and fungal cells can inform on nutrient accessibility and interspecific differences of mycorrhizal life forms. Here, we hypothesized that mycorrhizal fungal species exhibit interspecific differences in mineral nutrient concentrations and that the differences correlate with the mineral nutrient concentrations of their associated root cells. Abundant mycorrhizal fungal species of mature beech and ash trees in a long-term undisturbed forest ecosystem were the EcM Lactarius subdulcis, Clavulina cristata and Cenococcum geophilum and the AM Glomus sp. Mineral nutrient subcellular localization and quantities of the mycorrhizas were analysed after non-aqueous sample preparation by electron dispersive X-ray transmission electron microscopy. Cenococcum geophilum contained the highest sulphur, Clavulina cristata the highest calcium levels, and Glomus, in which cations and P were generally high, exhibited the highest potassium levels. Lactarius subdulcis-associated root cells contained the highest phosphorus levels. The root cell concentrations of K, Mg and P were unrelated to those of the associated fungal structures, whereas S and Ca showed significant correlations between fungal and plant concentrations of those elements. Our results support profound interspecific differences for mineral nutrient acquisition among mycorrhizas formed by different fungal taxa. The lack of correlation between some plant and fungal nutrient element concentrations may reflect different retention of mineral nutrients in the fungal part of the symbiosis. High mineral concentrations, especially of potassium, in Glomus sp. suggest that the well-known influence of tree species on chemical soil properties may be related to their mycorrhizal associates.     

垃圾填埋场渗滤液灌溉对土壤理化特征和草本花卉生长的影响

以草本花卉植物一串红和石竹为材料,通过盆栽试验研究了不同浓度垃圾渗滤液灌溉对土壤理化性质及生物学性质、植物生长、氮磷和重金属吸收的影响。渗滤液灌溉提高了土壤有机质、氮含量和电导率,其中,黄壤盐分积累速度大于紫色土,而对土壤磷和重金属含量的影响不明显,土壤脲酶活性随渗滤液浓度的提高呈先升高后降低趋势,紫色土和黄壤在渗滤液灌溉浓度分别为60%和40%时脲酶活性最强;随渗滤液浓度提高紫色土过氧化氢酶活性略为上升,黄壤过氧化氢酶活性降低。渗滤液灌溉使两种花卉根系生长受到抑制,但对植物地上部的生长发育存在低浓度促进高浓度抑制的双重作用。渗滤液灌溉可提高两种植物地上部的氮含量,对一串红磷含量影响不明显,使石竹磷含量降低,对Cu、Zn含量的影响因土壤和植物的不同而异,但高浓度渗滤液灌溉使两种植物Pb、Cr和Cd含量均提高。结果表明,适当浓度渗滤液灌溉具有改善土壤肥力,促进植物地上部生长发育的作用,渗滤液灌溉不会引起土壤和植物体内重金属过量积累,土壤氮过量积累导致的氮磷营养失调和盐分过度积累是高浓度渗滤液抑制植物生长的重要原因。从土壤性质变化和植物生长反应看,渗滤液灌溉浓度以20%—40%为佳。     

Inhibitory effects of leachate from Eupatorium adenophorum on germination and growth of Amaranthus retroflexus and Chenopodium glaucum

Amaranthus retroflexus L. and Chenopodium glaucum L. are two widely distributed destructive weeds. Their strong adaptability and massive seed production make them the hardest weeds to deal with. This present study intended to investigate the effect of leachate from Eupatorium adenophorum on the growth of these weeds and explore the potential to develop an environmental friendly strategy to use the leachate to control the weeds. Seeds of A. retroflexus L. and C. glaucum L. were soaked in solutions containing 0%, 0.6%, 1.25%, 2.5%, and 5% leachate from E. adenophorum leaves. A. retroflexus and C. glaucum seedlings grown in pots were sprayed with leachate solutions in the same concentration range. The effects of these leachate solutions on membrane permeability and germination of seeds, and growth and physiological characteristics of the seedlings were investigated. The highest concentration of leachate (5%) caused significant damage to the cell membrane of seeds of both weed species, whereas lower concentrations (0.6%) promoted repair of the membrane system, as reflected by higher and lower than control in relative conductivity (RC), respectively. Different concentrations of leachate showed distinct allelopathic inhibitory effects on the two weed species; lower concentrations showed weak inhibitory or even positive effects, whereas higher concentrations showed stronger inhibitory effects. Higher concentrations of leachate (2.5% and 5%) delayed germination and significantly decreased the emergence rate of the seeds, survival rate, and dry matter accumulation of the seedlings. When treated by 5% leachate, the emergence date of A. retroflexus was delayed by 3.6 d, emergence rate of the seeds and survival rate was 69.1% and 70.6% of the control, respectively, seedling dry matter was 48.6% less than the control; In the case of C. glaucum, the emergence date was delayed by 2.7 d, emergence rate of the seeds and survival rate was 45.1% and 58.6% of the control, respectively, seedling dry matter was 44.7% less than the control. There were significant interactions among the different concentrations of leachate and the length of treatment period with respect to activities of antioxidant enzymes, malondialdehyde (MDA) contents, and chlorophyll contents. Seedlings treated with 0.6%, 1.25%, or 2.5% leachate solution for 24–72 h showed increased superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities. When seedlings were treated with leachate solutions for 96 h, antioxidant enzyme activities and chlorophyll content decreased in A. retroflexus, but only CAT activity decreased in C. glaucum. When seedlings of the two weed species were treated with 5% leachate solution, CAT activity and chlorophyll content decreased and MDA content gradually increased with longer treatment times (from 24 to 96 h). The two weed species showed different allelopathic responses to E. adenophorum; A. retroflexus was more sensitive than C. glaucum. Based on the investigation, it could be speculated that the delayed germination and low germination rate of the weeds after treatment by leachate could be due to the fact that leachate damaged the membrane system of the seeds. By delaying germination, lowering the germination rate of the weeds and inhibiting seedling growth, leachate from E. adenophorum could provide an effective way of controlling the weeds.     

Fractionation of Heavy Metals in Mine Tailings Amended with Composted Manure

This study evaluated the effect of composted cow manure (CCM) on the chemical fractionation and retention degree of heavy metals (HMs) in mine tailings from Zimapán, México. In a greenhouse experiment, mine tailings from three deposits were incubated for 3 months; experimental units were placed in a PVC container, where increasing doses of CCM were applied. HM pseudo-total concentrations, HM extractions with ethylenediaminetetraacetic acid (EDTA, 0.05 M), and a sequential chemical extraction (SCE) were carried out. The HM concentrations were determined by atomic absorption spectrophotometry. The pseudo-total concentrations of Pb, Cu, Cd, and Ni found were up to 1506, 206, 27, and 23 mg kg^?1, respectively; extractable Pb was up to 42%; 21% for Cu; 51% for Cd; and 16% of Ni of the pseudo-total concentrations of each metal. Treatment with 12% of CCM in mine tailing decreased EDTA-extractable HM concentrations, while the SCE revealed a decrease in exchangeable fraction and an increase in the organic fraction of HM. A positive correlation between CCM application and organic fractions of HMs was found, although the highest increasements were recorded in the organic fraction.     

Effectiveness of wood ash containing charcoal as a fertilizer for a forest plantation in a temperate region

Amendment of forest soils with mixed wood ash (MWA) generated in biomass power plants can prevent the depletion of soil nutrients that results from the intensive harvesting of forest plantations. Unlike fly wood ash, MWA contains charcoal and is characterized by a lower release of nutrients, so that it might be useful as a long term source of nutrients and soil organic matter. However, in order to use MWA as a fertilizer in forest systems, its effectiveness as regards supplying P and N must be improved. These aspects were studied in a 4 year-trial carried out in a Pinus radiata plantation. MWA was added alone or with mineral P, and the results were compared with those obtained with a combination of Ca(OH)₂ and mineral P. The application of MWA together with mineral P fertilizer increased the nutrient supply to the trees, as revealed by the changes in nutrient concentrations, lower values of resorption efficiencies and improved tree growth. The results showed that the amounts of Ca, Mg and K supplied by the MWA were suitable for maintenance of soil reserves. However, the presence of charcoal may have decreased the availability of P. The application of the MWA led to lower soil N mineralization rates and mineral N concentrations, which may affect N-limited systems. The use of density-dependent single tree increment models enabled the positive effects on tree growth of fertilization and thinning to be distinguished. For the treatments supplemented with mineral P, multiplicative factors of 1.13 to 1.15 can be applied to obtain post-thinning predictions of 4-year single-tree basal area increments. Although MWA can be used as a long term source of nutrients, charcoal temporarily reduces the availability of P and N.     

Bioaccessibility and safety assessment of trace elements from decoction of “Zhebawei” herbal medicines by in vitro digestion method

Studies on in vitro bioaccessibility and safety assessment of 6 elements namely Fe, Zn, Cu, Mn, As and Cd in decoction of eight commonly consumed “Zhebawei” herbal medicines were carried out. The method was based on simulation of human digestion in the gastrointestinal tract. Total content and content in extracts from gastrointestinal phases were analyzed for these elements by inductively coupled plasma atomic emission spectrometer (ICP-AES). In decoction of all 8 herbal medicines, it was found that the total content and bioaccessible concentration of these elements varied considerably among the types of herb, and the total content of each element did not show linearity with their bioaccessible content of the corresponding element. There is no risk of adverse health effects resulting from overdose of Fe, Zn, Cu, and Mn for almost all individuals by ingesting recommended maximum daily dose of these eight herbal medicines. In terms of Cd only Ophitopogin japonicum had higher total concentration and bioaccessible content than the value of suggested limit (5.4 μg/d). For total As content, only Scrophularia ningpoensis and Corydalis yanhusuo did not meet the safety standard. However, regarding bioaccessible As contents, none of the eight herbal medicines exceeded the value of the daily permissible intake of As (0.12 mg). The risk of toxicity from an element in herbal medicine might be overestimated when the total concentration but not the bioaccessible content is taken into account. In vitro digestion method is rapid, relatively simple and inexpensive, which could be helpful in conducting experiments about safety assessment of an element in herbal medicines.     

Opportunistic Pathogens and Elements of the Resistome that Are Common in Bottled Mineral Water Support the Need for Continuous Surveillance

Several differences concerning bacterial species, opportunistic pathogens, elements of the resistome as well as variations concerning the CFU/mL counts were identified in some of the five most marketed bottled mineral water from Araraquara city, São Paulo, Brazil. Two out of five brands tested were confirmed as potential source of opportunistic pathogens, including Mycobacterium gordonae, Ralstonia picketti and Burkholderia cepacia complex (Bcc). A total of one hundred and six isolates were recovered from four of these bottled mineral water brands. Betaproteobacteria was predominant followed by Alphaproteobacteria, Gammaproteobacteria and Firmicutes. Ninety percent of the bacteria isolated demonstrated resistance to seventeen of the nineteen antimicrobials tested. These antimicrobials included eight different classes, including 3rd and 4th generation cephalosporins, carbapenems and fluoroquinolones. Multidrug resistant bacteria were detected for fifty-nine percent of isolates in three water brands at counts up to 10³ CFU/ml. Of major concern, the two bottled mineral water harboring opportunistic pathogens were also source of elements of the resistome that could be directly transferred to humans. All these differences found among brands highlight the need for continuous bacteriological surveillance of bottled mineral water.     

Influence of Soil Moisture on Soil Solution Chemistry and Concentrations of Minerals in the Calcicoles Phleum phleoides and Veronica spicata Grown on a Limestone Soil

Veronica spicata and Phleum phleoides are calcicole plants,mainly occurring on neutral or alkaline soil. An experimentof 16 weeks duration was performed in a glasshouse with theobjective of elucidating the influence of soil moisture levelon soil solution chemistry, and biomass concentrations and uptakeof mineral nutrients by the plants. Seven levels of moisture,corresponding to 35–85% of the water holding capacity(WHC) of the soil, were tested. Soil solution HCO₃, P and Mnconcentrations, and pH, increased, whereas Ca, Mg and Zn concentrationsdecreased, with increasing soil moisture. Concentrations ofK were highest at 50–70% WHC. Concentrations and amountsof P, Zn and Mn in the two species were usually related to soilsolution concentrations; these are elements with low solubilityand availability in calcareous soils. Concentrations of nutrientsin biomass were more influenced by soil moisture in V. spicatathan inP. phleoides . This indicates that P. phleoides is morecapable of controlling its uptake of mineral nutrients, whereasV. spicata is sensitive to variations in soil moisture. It isconcluded that variation in soil moisture regime may greatlyinfluence concentrations of mineral nutrients in calcareoussoil solutions and their uptake by plants. Species able to utilizethese solubility fluctuations may have an advantage in competitionfor nutrients. Variation in soil moisture content might evenbe a prerequisite for adequate acquisition of mineral nutrientsand growth of plants on limestone soils, thereby influencingthe field distribution of native plants among habitats. Copyright1999 Annals of Botany Company Calcareous, calcicole, concentration, mineral, moisture, nutrient, Phleum phleoides, soil, soil solution, uptake, Veronica spicata, water.     

Control of seed coat thickness and permeability in soybean : a possible adaptation to stress

Although the seed coat, through its thickness and permeability, often regulates seed germination, very little is known about the control of its development. Using soybean (Glycine max [L.] Merrill) explants, podbearing cuttings in which defined solutions can be substituted for the roots, we have demonstrated that cytokinin and mineral nutrients moving through the xylem can control soybean seed coat development. Lack of cytokinin and minerals in the culture solution, causes a thicker, less permeable seed coat to develop. The seeds with thickened coats will imbibe water rapidly if scarified; furthermore, these scratched seeds also germinate and produce normal plants. Inasmuch as stress (e.g. drought) decreases mineral assimilation and cytokinin production by the roots, the resulting delay in germination could be an adaptive response to stress.     

Possible mineral contributions to the diet and health of wild chimpanzees in three East African forests

We present new data on the ingestion of minerals from termite mound soil by East African chimpanzees (Pan troglodytes schweinfurthii) living in the Budongo Forest Reserve, Uganda, the Gombe National Park and the Mahale Mountains National Park, Tanzania. Termite mound soil is here shown to be a rich source of minerals, containing high concentrations of iron and aluminum. Termite mound soil is not, however, a source of sodium. The concentrations of iron and aluminum are the highest yet found in any of the mineral sources consumed. Levels of manganese and copper, though not so high as for iron and aluminum, are also higher than in other dietary sources. We focus on the contribution of termite mound soil to other known sources of mineral elements consumed by these apes, and compare the mineral content of termite soil with that of control forest soil, decaying wood, clay, and the normal plant‐based chimpanzee diet at Budongo. Samples obtained from Mahale Mountains National Park and Gombe National Park, both in Tanzania, show similar mineral distribution across sources. We suggest three distinct but related mechanisms by which minerals may come to be concentrated in the above‐mentioned sources, serving as potentially important sources of essential minerals in the chimpanzee diet.     

Nutrient influences on toxicity and carcinogenicity

Essential nutrients and toxicants often coexist in the diet of humans and animals. Interactions among nutrients and chemicals in the diet may alter the toxicity of the chemical or the requirement for or availability of specific nutrients. Such interactions have been demonstrated among toxins and dietary protein, trace elements, and vitamins. Certain nutrients may also alter the response to certain drugs, and some drugs, such as oral contraceptives, may alter the availability of some nutrients. The carcinogenicity of some compounds and the subsequent promotion of tumor growth are affected by nutrients such as fat, vitamins, and lipotropes and by such minor dietary constituents as naturally occurring indoles and synthetic preservatives. In this paper we review such interactions as well as the mechanisms responsible for them.     

Ecological responses and remediation ability of water fern (Azolla japonica) to water pollution

The ability of the water fern Azolla japonica to remediate phosphorus (P), nitrogen (N), and iron (Fe) contamination, and its physiological responses to three common sources of water pollution (landfill leachate, swine lagoon sewage, and fish farm sewage) and standard solution were investigated. The biomass, water content, and chlorophyll content of Azolla japonica in each solution were measured, and the concentrations and accumulation rates of polluting elements in the solutions were determined. A. japonica showed over eight-fold increase in biomass within only 20 d in every solution except in swine lagoon sewage, extremely high in N concentration. Consistent chlorophyll and water contents of the plant in most solutions showed that A. japonica can adapt to highly concentrated solutions. N, P, and Fe concentrations of the solutions decreased significantly within the 20 d. In most treatments, A. japonica showed high N accumulation and also showed total uptake of P and Fe from the solutions. In reference to this result, using this species as a phytoremediator plant would have additional benefits of helping maintaining endangered populations of A. japonica. Therefore, the plant??s fast growth, good element remediation efficiency, and conservation needs makes A. japonica a suitable plant species for pollution remediation.     

An Integrated Approach Combining Chemical Analysis and an In Vivo Bioassay to Assess the Estrogenic Potency of a Municipal Solid Waste Landfill Leachate in Qingdao

Various adverse effects related to landfill leachate have made leachates an important issue in past decades, and it has been demonstrated that landfill leachate is an important source of environmental estrogens. In this study, we employed chemical analysis of some already evaluated estrogenic substances, in combination with a bioassay using several specific biomarkers (e.g., plasma vitellogenin and sex steroids, enzyme activity of gonad gamma-glutamyl transpeptidase, and gonadosomatic index) to evaluate the estrogenic activities in outlets from different stages of the leachate treatment process. The results indicated that 5 environmental estrogens (4-t-octylphenol, bisphenol A, di-ethyl phthalate, di-n-butyl phthalate, and diethylhexyl phthalate) were detected by a gas chromatography-mass spectrometry, and the concentrations in leachate samples were 6153 ng/L, 3642 ng/L, 2139 ng/L, 5900 ng/L, and 9422 ng/L, respectively. Leachate (1∶200 diluted) induced the synthesis of plasma vitellogenin and led to decreased enzyme activity of gonad gamma-glutamyl transpeptidase and gonadosomatic index in male goldfish (Carassius auratus) after a 28-day exposure, while increased circulating 17β-estradiol level was also observed in males exposed to treated effluent. Although the target EEs were partially removed with removal rates varying from 87.2% to 99.77% by the “membrane bioreactor+reverse osmosis+aeration zeolite biofilter” treatment process, the treated effluent is still estrogenic to fish. The method combined chemical techniques with the responses of test organisms allowing us to identify the group of estrogen-like chemicals so that we were able to evaluate the overall estrogenic effects of a complex mixture, avoiding false negative assessments.     

What controls plant nutrient use in high elevation ecosystems?

The importance of rock-derived mineral nutrients (P, K, Mn, Mg, and Ca) in plant physiological function is well established. However, one important and relatively unexplored question is whether or not the same rules of plant nutrient use efficiency apply to these essential elements even if they are not limiting to primary production. We examined conifer growth and nutrient use dynamics across sites with contrasting geologies (sedimentary and volcanic) that vary in both rock-derived mineral nutrient and N availability. Differences in bedrock geochemistry generally corresponded to differences in available soil nutrients, such that the volcanic site tended to have greater available nutrients. Foliar nutrient concentrations reflected both differences in bedrock chemistry and indices of available soil nutrients for P, K, and Mn. Aboveground biomass production did not follow expected patterns and was greater for trees growing on low nutrient sites, but only with respect to the annual woody increment. Fine litter production did not differ between sites. Finally, we found evidence for trade-offs between two commonly examined components of nutrient use efficiency (NUE): nutrient productivity (A _n) and mean residence time of nutrients. However, we did not find evidence for higher plant NUE in soils with lower nutrient availability for N or rock-derived nutrients.     

Calcium-Enhanced Twitching Motility in Xylella fastidiosa Is Linked to a Single PilY1 Homolog

The plant-pathogenic bacterium Xylella fastidiosa is restricted to the xylem vessel environment, where mineral nutrients are transported through the plant host; therefore, changes in the concentrations of these elements likely impact the growth and virulence of this bacterium. Twitching motility, dependent on type IV pili (TFP), is required for movement against the transpiration stream that results in basipetal colonization. We previously demonstrated that calcium (Ca) increases the motility of X. fastidiosa, although the mechanism was unknown. PilY1 is a TFP structural protein recently shown to bind Ca and to regulate twitching and adhesion in bacterial pathogens of humans. Sequence analysis identified three pilY1 homologs in X. fastidiosa (PD0023, PD0502, and PD1611), one of which (PD1611) contains a Ca-binding motif. Separate deletions of PD0023 and PD1611 resulted in mutants that still showed twitching motility and were not impaired in attachment or biofilm formation. However, the response of increased twitching at higher Ca concentrations was lost in the pilY1-1611 mutant. Ca does not modulate the expression of any of the X. fastidiosa PilY1 homologs, although it increases the expression of the retraction ATPase pilT during active movement. The evidence presented here suggests functional differences between the PilY1 homologs, which may provide X. fastidiosa with an adaptive advantage in environments with high Ca concentrations, such as xylem sap.     

Biofortification of crops with seven mineral elements often lacking in human diets – iron, zinc, copper, calcium, magnesium, selenium and iodine

The diets of over two-thirds of the world's population lack one or more essential mineral elements. This can be remedied through dietary diversification, mineral supplementation, food fortification, or increasing the concentrations and/or bioavailability of mineral elements in produce (biofortification). This article reviews aspects of soil science, plant physiology and genetics underpinning crop biofortification strategies, as well as agronomic and genetic approaches currently taken to biofortify food crops with the mineral elements most commonly lacking in human diets: iron (Fe), zinc (Zn), copper (Cu), calcium (Ca), magnesium (Mg), iodine (I) and selenium (Se). Two complementary approaches have been successfully adopted to increase the concentrations of bioavailable mineral elements in food crops. First, agronomic approaches optimizing the application of mineral fertilizers and/or improving the solubilization and mobilization of mineral elements in the soil have been implemented. Secondly, crops have been developed with: increased abilities to acquire mineral elements and accumulate them in edible tissues; increased concentrations of 'promoter' substances, such as ascorbate, β-carotene and cysteine-rich polypeptides which stimulate the absorption of essential mineral elements by the gut; and reduced concentrations of 'antinutrients', such as oxalate, polyphenolics or phytate, which interfere with their absorption. These approaches are addressing mineral malnutrition in humans globally.     

Effects of mineral turbidity on freshwater plankton communities: Three exploratory tank experiments of factorial design

We conducted three exploratory experiments of factorial design on the effects of mineral turbidity in 18 large (7 000 1) fiberglass tanks containing plankton communities derived from Lake Texoma (Oklahoma-Texas), a large reservoir often subject to turbid inflows. Replicate plankton communities developed for 30–45 d in response to 4–9 treatments of planktivorous fish, dead fish, nutrient additions and artificial removal of zooplankton with plankton netting (or combinations of these manipulations). In one experiment we then added three concentrations of kaolin and in the other two experiments we added bentonite or powdered silica to the replicate tank communities. We measured the responses of the diverse plankton communities to the addition of mineral turbidity for an additional period of 30–45 d.Effects of introduced minerals (quality or concentration effects) and food web treatments after mineral addition (fish, nutrients, etc.) were determined by analysis of covariance after observations were adjusted for the value of each response variable at the time of mineral addition. Covariance analysis resulted in a statistical model explaining > 80% of the variance for most response variables. The values of response variables at the time of mineral addition were often the most important source of variation, suggesting the importance of biotic community resiliency to the effects of mineral turbidity. There were few effects of mineral particles on physical or chemical (temperature, conductivity, oxygen, pH), nutrient (nitrate, phosphate, alkalinity) or biotic (algal or zooplankton populations) components of the tank communities. Mineral effects were found for several measures of water clarity (Secchi depth, turbidity, and the concentration of small sestonic particles).     

Arbuscular mycorrhizal fungi affect glucosinolate and mineral element composition in leaves of Moringa oleifera

Moringa is a mycorrhizal crop cultivated in the tropics and subtropics and appreciated for its nutritive and health-promoting value. As well as improving plant mineral nutrition, arbuscular mycorrhizal fungi (AMF) can affect plant synthesis of compounds bioactive against chronic diseases in humans. Rhizophagus intraradices and Funneliformis mosseae were used in a full factorial experiment to investigate the impact of AMF on the accumulation of glucosinolates, flavonoids, phenolic acids, carotenoids, and mineral elements in moringa leaves. Levels of glucosinolates were enhanced, flavonoids and phenolic acids were not affected, levels of carotenoids (including provitamin A) were species-specifically reduced, and mineral elements were affected differently, with only Cu and Zn being increased by the AMF. This study presents novel results on AMF effects on glucosinolates in leaves and supports conclusions that the impacts of these fungi on microelement concentrations in edible plants are species dependent. The nonspecific positive effects on glucosinolates and the species-specific negative effects on carotenoids encourage research on other AMF species to achieve general benefits on bioactive compounds in moringa.