Reduced Fe Concentrations Research Articles

Combined Application of Biochar and Silicon Fertilizer for Improved Soil Properties and Maize Growth

Biochar can be a good soil amendment to reduce the soil pH, increase crop growth rate, and improve the efficient use of fertilizer. Other than that, silicon fertilizer also would promote photosynthetic ability on plant development that would help to produce high yield. In this work, a series of experiments was conducted to observe the effect of rice husk biochar and silicon fertilizer on the maize growth rate and soil pH. A 45-day pot experiment in the greenhouse with three replicates of 9 experimental treatment combinations of RHB at two rates (5 and 2.5 t.ha-1) with silicon fertilizer at three rates (125%, 100%, 75%), sole biochar (10 t.ha-1), sole silicon fertilizer (100%) and control (NPK) to observe the best rate and combination to improve growth rate and change in soil chemical in acid soil. The result showed that the co-application of sole biochar and biochar with Silicon significantly improved growth development, increased photosynthesis rate, altered soil pH, and reduced Fe concentration compared to control. The plant height increased 88.35% from T4 (5 t.ha-1 RHB + 100% Si) compared to the control and the conductance was higher in T4 (0.53) followed by T8 (0.438) while T1 (0.071) recorded the lowest conductance. The shoot fresh weight was higher in T4 (127.83 g) followed by T8 (57.14 g). However, the weight increased by 343.7% at T4 followed by T8 (2.5 t.ha-1 RHB + 75% Si) at 98.33%. The highest pH increment of 1.24 units (T1 = 5.53, T4 = 6.77) of soil pH was noted from T4 (5 t.ha-1 RHB + 100% Si) compared to control (NPK), and the highest total Fe in soil was observed from T1 (442.30 mg.kg-1). The current study results showed that T4 (50% RHB + 100% Silicon) was the best treatment over the other rates of RHB and silicon increased plant height, photosynthetic rate, and biomass.

High‐Remanence Fe‐Rich 2:17‐Type Sm–Co Sintered Magnets Mediated via Multiscale Microstructure

Realizing high remanence in Fe‐rich 2:17‐type Sm–Co sintered magnets remains a challenge when Fe content exceeds 23 wt%. Herein, a record remanence of 12.42 kGs is obtained by multiscale microstructure regulation strategy, based on co‐optimization from pulverizing treatment to solid solution and aging treatment. The density of sintered magnets is significantly enhanced by refining magnetic powders using ball milling to reduce porosity. Grain boundary precipitation phase is eliminated via prolonging solid solution time, together with reduced Fe concentration in the cell boundaries, due to increased proportion of defected 1:3R planar Z phase. Furthermore, the proportion of 1:3R planar Z phase is increased by greatly reducing the 2:17R’ phase during appropriately isothermal aging temperature to reduce Fe concentration in cell boundaries and the remanence of the magnet increases. The studies deepen the understanding of the correlation among process, microstructure, and remanence, guiding the preparation of Fe‐rich 2:17‐type Sm–Co sintered magnets with high magnetic performance.

Iron dynamics and isotope fractionation in soil and rice during 2000 years of rice cultivation

Abstract Background and aims Paddy management results in frequent redox cycles of the soil and thus changes in the terrestrial iron (Fe) cycle. We intended to test that the increasing duration of paddy management and the increasing frequency of soil redox cycles leave their fingerprint on Fe isotope composition of paddy systems, which could subsequently be used to deduce the origin of rice plants as related to the extent of past soil paddy management. Methods We sampled soil and rice plants of a paddy chronosequence in China with rice cultivation history up to 2000 years and determined the changes of soil Fe pools and Fe isotope composition of the soil and rice plants. Results Prolonged paddy management reduced Fe concentrations in submerged topsoil leading to an enrichment of heavy Fe isotopes, with the δ56Fe values 0.12‰ heavier than the parent material after 2000 years. Particularly, Fe oxides were lost quickly, while exchangeable and organic-associated Fe continuously accumulated during paddy management and played an increasing role in the plant-available Fe pool in the topsoil. The Fe content in rice also increased with paddy age, while its Fe isotope composition did not reflect that of paddy soil but resembled that of the Fe plaques on the roots. Conclusion Prolonged rice cropping altered the biological contribution in the terrestrial Fe cycle. However, while soil Fe pools that are closely linked with biological activities were affected rather quickly, the changes in the whole soil Fe system were detectable only after a millennium of paddy management.

Effects of Selenium Supplementation on the Ion Homeostasis in the Reproductive Organs and Eggs of Laying Hens Fed With the Diet Contaminated With Cadmium, Lead, Mercury, and Chromium

The objective of this study was to explore the toxic effects of different heavy metals in combination with their deposition and ion homeostasis in the reproductive organs and eggs of laying hens, as well as the alleviating action of selenized yeast. A total of 160 Lohmann pink-shell laying hens (63-week-old) were randomly allocated into four treatments with 10 replicates of four hens each. The four dietary treatments were the corn-soybean meal basal dietary (control; CON); the CON dietary supplemented with 0.4 mg/kg selenium from selenized yeast (Se); the CON dietary supplemented with 5 mg/kg Cd + 50 mg/kg Pb +3 mg/kg Hg + 5 mg/kg Cr (HEM), and the HEM dietary supplemented with 0.4 mg/kg selenium from selenized yeast (HEM+Se). The dietary HEM significantly increased Cd, Pb, and Hg deposition in the egg yolk and ovary, and Cd and Hg deposition in the oviduct and in the follicular wall (p < 0.05). The HEM elevated Fe concentration in the egg yolk, ovary, and oviduct (p < 0.05). The HEM decreased Mn concentration in the egg yolk, Fe, Mn, and Zn concentrations in the egg white, Cu concentration in the ovary, Mg concentration in the oviduct, as well as Ca, Cu, Zn, and Mg concentrations in the follicular walls (p < 0.05). Dietary Se addition elevated Se concentration in the egg yolk, oviduct, and follicular walls and Mg concentration (p < 0.05) in the oviduct, whereas it reduced Fe concentration in the oviduct compared with the HEM-treated hens. Some positive or negative correlations among these elements were observed. Canonical Correlation Analysis showed that the concentrations of Pb and Hg in the egg yolk were positively correlated with those in the ovary. The concentration of Cd in the egg white was positively correlated with that in the oviduct. In summary, dietary Cd, Pb, Hg, and Cr in combination caused ion loss and deposition of HEM in reproductive organs of laying hens. Dietary Se addition at 0.4 mg/kg from selenized yeast alleviated the negative effects of HEM on Fe and Mg ion disorder in the oviduct and follicle wall of hens.

Identification of Quantitative Trait Loci Associated With Iron Deficiency Tolerance in Maize.

Iron (Fe) is a limiting factor in crop growth and nutritional quality because of its low solubility. However, the current understanding of how major crops respond to Fe deficiency and the genetic basis remains limited. In the present study, Fe-efficient inbred line Ye478 and Fe-inefficient inbred line Wu312 and their recombinant inbred line (RIL) population were utilized to reveal the physiological and genetic responses of maize to low Fe stress. Compared with the Fe-sufficient conditions (+Fe: 200 μM), Fe-deficient supply (−Fe: 30 μM) significantly reduced shoot and root dry weights, leaf SPAD of Fe-efficient inbred line Ye478 by 31.4, 31.8, and 46.0%, respectively; decreased Fe-inefficient inbred line Wu312 by 72.0, 45.1, and 84.1%, respectively. Under Fe deficiency, compared with the supply of calcium nitrate (N1), supplying ammonium nitrate (N2) significantly increased the shoot and root dry weights of Wu312 by 37.5 and 51.6%, respectively; and enhanced Ye478 by 23.9 and 45.1%, respectively. Compared with N1, N2 resulted in a 70.0% decrease of the root Fe concentration for Wu312 in the −Fe treatment, N2 treatment reduced the root Fe concentration of Ye478 by 55.8% in the −Fe treatment. These findings indicated that, compared with only supplying nitrate nitrogen, combined supply of ammonium nitrogen and nitrate nitrogen not only contributed to better growth in maize but also significantly reduced Fe concentration in roots. In linkage analysis, ten quantitative trait loci (QTLs) associated with Fe deficiency tolerance were detected, explaining 6.2–12.0% of phenotypic variation. Candidate genes considered to be associated with the mechanisms underlying Fe deficiency tolerance were identified within a single locus or QTL co-localization, including ZmYS3, ZmPYE, ZmEIL3, ZmMYB153, ZmILR3 and ZmNAS4, which may form a sophisticated network to regulate the uptake, transport and redistribution of Fe. Furthermore, ZmYS3 was highly induced by Fe deficiency in the roots; ZmPYE and ZmEIL3, which may be involved in Fe homeostasis in strategy I plants, were significantly upregulated in the shoots and roots under low Fe stress; ZmMYB153 was Fe-deficiency inducible in the shoots. Our findings will provide a comprehensive insight into the physiological and genetic basis of Fe deficiency tolerance.

Circumpolar Deep Water and Shelf Sediments Support Late Summer Microbial Iron Remineralization

AbstractDespite widespread iron (Fe) limitation in the Southern Ocean, intense phytoplankton blooms are observed around productive coastal regions such as the Mertz Polynya (off George V Land and Adelie Land, East Antarctica; 140–155°E). Sources of Fe across coastal East Antarctica vary, with limited data available for late summer months. We investigated the sources of dissolved Fe (dFe; &lt;0.2 μm) at 19 oceanographic stations in the Mertz Glacier Region (64–67°S; 138–154°E), between January and March of 2019. Concentrations of dFe ranged from below detection limit (0.03 nM) at the surface, to 0.34 nM above the base of the mixed layer (35 m), reaching 0.59 nM at depth (520 m). Using oceanographic features and trace element ratios (manganese and titanium), we identified Circumpolar Deep Water (CDW) and shelf sediment resuspension in modified CDW as contributors of dFe to the region over this period. Microbial Fe remineralization was evident where nutrient‐rich water met highly oxygenated waters over the continental shelf. Reduced Fe concentrations in the mixed layer and euphotic zones suggested rapid biological uptake prior to sampling. Despite proposals for pelagic Fe recycling by marine animals, preliminary investigations reveal no significant spatial relationship between animal presence and surface ocean Fe concentrations over the study area. Further research is required to identify seasonal changes to Fe supply in coastal areas which will strengthen our understanding of the Fe cycle and its influence on microbial and primary productivity in this globally significant region.

Redistribution of iron oxides in aggregates induced by pe + pH variation alters Cd availability in paddy soils

In this study, the effect of unstable pe + pH levels on the transformation of Fe oxides in different-sized soil fractions and its impact on Cd speciation were explored. Paddy soil samples collected from two locations in China were cultivated for two months under one of four pe + pH conditions: flooding + N2 (T1), flooding (T2), 70% water holding capacity (T3), and 70% water holding capacity + O2 (T4). Chemical analysis and X-ray diffraction (XRD) were used to identify the mineralogical phases and species of Fe and Cd in paddy soils. The results show that the decrease of soil pe + pH level favored the transformation of well-crystallized Fe oxides (Fec), such as hematite and goethite, into poorly-crystallized (Feo) and organically-complexed (Fep) forms. The transformation promoted the binding of Cd to Fe oxides and was primarily responsible for up to a 41.8% decrease of soil DTPA (diethylenetriaminepentaacetic acid)-extractable-Cd content. In addition, the decline in pe + pH value reduced Fe concentrations in soil particle fractions of 0.2–2-mm (17.8%–30.6%) and <0.002-mm (20.7%–31.7%) of the two flooding treatments. The decreased Fe concentrations were closely associated with less Fec contents in these same fractions and more Feo and Fep in coarser aggregates (P < 0.01). Importantly, the increase in contents of Feo and Fep in the 0.002–2 mm fraction were significantly correlated with content of Fe-/Mn-oxide-bound Cd (OX-Cd) in larger particle-size fractions (P < 0.01). Furthermore, the increasing content of OX-Cd played a crucial role in reducing DTPA-Cd content. This study demonstrates that low pe + pH values favor the transformation of crystalline Fe oxides into a poorly-crystallized and organically-complexed phase, which facilitates Cd accumulation in coarser aggregates and enhances Cd stability in paddy soils.

Observation of exchange bias in nanoscale AuFe alloy film

We report on observation of the exchange bias effect in AuFe co-sputtered alloy films in the as-deposited state and following swift heavy ion irradiation. The Mössbauer spectrum for the as-deposited film shows a broad paramagnetic doublet together with a small contribution from hyperfine magnetic sextets. The magnetization behavior exhibits a spontaneous exchange bias effect at room temperature without application of an external triggering field. The magnitude of exchange bias in the as-deposited sample increases with decreasing temperature, at first gradually down to about 50 K and then more rapidly down to 5 K. Irradiation of AuFe film with 100 MeV Au9+ ions transforms the Mössbauer spectrum into a broad magnetic sextet, with asymmetric broadening characteristic of the formation of α-Fe magnetic nanoclusters surrounded by shells of reduced Fe concentration. At room temperature the exchange bias field is in the same sense as that for the as-deposited sample, but decreases with temperature until it reverse its sign at below about 50 K. In both the as-deposited and irradiated samples a well-defined uniaxial magnetic anisotropy, consequent on a stress induced texturing of the Fe precipitate distribution, is observed.

A transcription factor OsbHLH156 regulates Strategy II iron acquisition through localising IRO2 to the nucleus in rice.

Plants have evolved two strategies to acquire ferrous (Strategy I) or ferric (Strategy II) iron from soil. The iron-related bHLH transcription factor 2 (IRO2) has been identified as a key regulator of iron acquisition (Strategy II) in rice. However, its mode of action, subcellular localisation and binding partners are not clearly defined. Using RNA-seq analyses, we identified a novel bHLH-type transcription factor, OsbHLH156. The function of OsbHLH156 in Fe homeostasis was analysed by characterisation of the phenotypes, elemental content, transcriptome, interaction and subcellular localisation of OsbHLH156 and IRO2. OsbHLH156 is primarily expressed in the roots and transcript abundance is greatly increased by Fe deficiency. Loss of function of OsbHLH156 resulted in Fe-deficiency-induced chlorosis and reduced Fe concentration in the shoots under upland or Fe(III) supplied conditions. Transcriptome analyses revealed that the expression of most Fe-deficiency-responsive genes involved in Strategy II were not induced in the osbhlh156-1 mutant. Furthermore, OsbHLH156 was required for nuclear localisation of IRO2. We conclude that OsbHLH156 is required for a Strategy II uptake mechanism in rice, partnering with a previously identified 'master' regulator IRO2. Mechanistically it is required for the nuclear localisation of IRO2.

Cadmium-Induced Testicular Toxicity in Mice: Subacute and Subchronic Route-Dependent Effects

This study aimed to compare Cd exposure by intraperitoneal (i.p.) and oral routes, evaluating the testicular subacute and subchronic effects. Adult male mice were separated into three groups subdivided according to the experimental period (7 and 42days after Cd exposure: subacute and subchronic effects, respectively): one group received water and two groups received CdCl2 (1.2mg/kg i.p. and 24mg/kg oral). The testicular concentration of essential minerals and Cd, activity of antioxidant enzymes and markers of oxidative stress, histology, and testicular histomorphometry were evaluated. The subacute effect of oral Cd showed reduced Fe concentration, while Ca and Cu increased in this route. The subchronic effect promoted decreasing in Mg in i.p. and oral routes, whereas Zn decreased only in the oral, and the Fe concentration did not change. SOD activity decreased in the oral subacute evaluation and in both pathways, i.p. and oral routes, in the subchronic evaluation, while GST activity increased, and MDA concentration decreased. Labeling of apoptotic cells was increased in the subacute and subchronic evaluation. Seminiferous epithelium degeneration, death of germ cells, and Leydig cell damages occurred in i.p. and oral routes. However, these damages were more intense in the oral route, mainly evaluating the subchronic effects. The results confirm that the severity of Cd-induced testicular injury depends on the pathway, as well as the duration of exposure.

Investigation on the performance of Mo2N thin film as barrier layer against Fe in the flexible Cu(In,Ga)Se2 solar cells on stainless steel substrates

In the present work, flexible Cu(In,Ga)Se2 (CIGS) solar cells were prepared from annealing and post-selenization of electrodeposited Cu/In/Ga precursor layers on stainless steel (SS) substrates. The Mo2N thin film was fabricated by radio-frequency (RF) reactive magnetron sputtering deposition and was proposed as a barrier layer to restrain the diffusion of Fe into the CIGS film. It was observed that the insertion of a Mo2N barrier layer had no influence on the crystal structure nor the morphology of the Mo and CIGS films, as identified and confirmed by X-ray diffraction (XRD) analysis and field emission scanning electron microscopy (FESEM). In addition, secondary ion mass spectrometry (SIMS) analysis indicated that the Mo2N barrier layer significantly reduced the diffusion of Fe into the CIGS film. The performance of the flexible CIGS solar cell was dramatically improved due to the reduced Fe concentration in the CIGS film. Finally, the flexible CIGS solar cell with a Mo2N barrier layer demonstrated an enhanced conversion efficiency of 6.86%, compared to that of a solar cell (3.45%) without a Mo2N barrier layer.

Ethylene is critical to the maintenance of primary root growth and Fe homeostasis under Fe stress in Arabidopsis.

Iron (Fe) is an essential microelement but is highly toxic when in excess. The response of plant roots to Fe toxicity and the nature of the regulatory pathways engaged are poorly understood. Here, we examined the response to excess Fe exposure in Arabidopsis wild type and ethylene mutants with a focus on primary root growth and the role of ethylene. We showed that excess Fe arrested primary root growth by decreasing both cell elongation and division, and principally resulteds from direct external Fe contact at the root tip. Pronounced ethylene, but not abscisic acid, evolution was associated with excess Fe exposure. Ethylene antagonists intensified root growth inhibition in the wild type, while the inhibition was significantly reduced in ethylene-overproduction mutants. We showed that ethylene plays a positive role in tissue Fe homeostasis, even in the absence of iron-plaque formation. Ethylene reduced Fe concentrations in the stele, xylem, and shoot. Furthermore, ethylene increased the expression of genes encoding Fe-sequestering ferritins. Additionally, ethylene significantly enhanced root K(+) status and upregulated K(+)-transporter (HAK5) expression. Our findings highlight the important role of ethylene in tissue Fe and K homeostasis and primary root growth under Fe stress in Arabidopsis.

Impact of iron limitation on primary production (dissolved and particulate) and secondary production in cultured Trichodesmium sp.

Diazotrophic cyanobacteria play an important role in biogeochemical cycles of carbon and nitrogen and, hence, in oceanic productivity in the tropical and subtropical regions of the ocean. Although many studies have examined the impact of iron (Fe) limitation on particulate primary production and dinitrogen (N2) fixation in the colonial cyanobacterium Trichodesmium, none have looked at the impact of Fe limitation on the percentage extracellular release (PER) and secondary production (SP) in Fe-limited cultures of this cyanobacterium. Here, we present the results of a series of culture experiments during which we examined the impact of 3 concentrations of dissolved iron (DFe) on total primary production (TPP = dissolved + particulate primary production, i.e. DPP + PPP), PER and on SP. Under severe Fe limitation (5 nM DFe), biomass, growth rates, TPP and N2 fixation were strongly reduced, while PER increased relative to the rates ob served at the highest Fe concentration. Moreover, reducing Fe concentration induced an increase in the percentage of photosynthetically fixed C used for algal growth, while the percentage of C used to support algal respiration decreased. Reduced Fe concentrations also induced a decrease in SP and in the SP:DPP ratio, indicating that the efficiency of transfer of fixed carbon from autotrophic to heterotrophic processes is reduced. This suggests that Fe, either directly through influencing cellular processes or indirectly through influencing organic matter structure or nitrogen availability, is controlling SP and, thus, microbial carbon utilization. These results suggest that the amount of carbon entering into the microbial loop may be reduced under Fe limitation, thus leading to an accumulation of dissolved organic carbon with potentially important impacts on microbial carbon cycling and, ultimately, on the biological carbon pump

Grain yield, starch, protein, and nutritional element concentrations of winter wheat exposed to enhanced UV-B during different growth stages

In order to alleviate the damage of UV-B on plants, it is important to determine at which growth stages are plants more sensitive to enhanced UV-B. The objective of the study was to evaluate the effects of UV-B on wheat yield and quality during different growth stages. Enhanced UV-B during heading, flowering and the whole growth stages (UCK, from seedling to grain filling) decreased yield by 6.6, 4.4 and 9.6%, respectively. Protein content in grain was decreased by enhanced UV-B during flowering and UCK over the control. Amylose, amylopectin and total starch content were not affected by UV-B treatments. UCK treatment resulted in a decrease of nitrogen (N), phosphorus (P) and iron (Fe) concentrations, while zinc (Zn) and manganese (Mn) concentrations increased. Enhanced UV-B during tillering, heading and flowering stages reduced Fe concentration, but increased Mn, copper (Cu) and Zn (except for flowering) concentrations. The results indicated that the changes in wheat yield and quality induced by enhanced UV-B during the whole growth stage were probably from the effects of UV-B radiation during heading and flowering stages. Therefore, to better defend the damage of UV-B to wheat, some methods should be undertaken during heading and flowering stages.

Identification of OsbHLH133 as a regulator of iron distribution between roots and shoots in Oryza sativa

Iron (Fe) is an essential micronutrient element for plant growth. Regulation of Fe-deficiency signalling networks is one of the many functions reported for basic helix-loop-helix (bHLH) transcription factors in plants. In the present study, OsbHLH133 was found to be induced by Fe-deficiency conditions in Oryza sativa. Insertional inactivation of OsbHLH133 (bhlh133) resulted in growth retardation, with enhanced Fe concentration seen in shoots, and reduced Fe concentration in roots. Overexpression of OsbHLH133 had the opposite effect, that is resulted in an enhanced Fe concentration in roots and reduced Fe concentration in shoots and also in xylem sap. Microarray analysis showed that some of the genes encoding Fe-related functions were up-regulated under Fe-sufficient conditions, in bhlh133 mutant plants compared to wild-type plants. Significant differential expression of a number of signalling pathways, including calcium signalling, was also seen in bhlh133 plants compared to wild-type plants, independent of Fe conditions.

Constructed wetlands for advanced treatment of wastewater with a complex matrix from a metal-processing plant: Bioconcentration and translocation factors of various metals in Acorus gramineus and Cyperus alternifolius

A flow-through constructed wetland (CW) has provided advanced treatment of wastewater with a complex matrix from a metal-processing plant. The main CW system (length 20 m, width 46 m, depth 0.3 m) was planted with aquatic plants such as Acorus gramineus, Cyperus alternifolius L., Iris pseudacorus, Lythrum anceps, Myosotis scorpioides, Phyla nodiflora L., and Zantedeschia aethiopica. During August–November 2007, the main CW system reduced total organic carbon concentrations from 5.7 to 1.2 mg/l, total nitrogen from 23.2 to 19.0 mg/l, and NH 4 +-N from 6.8 to 4.0 mg/l, on average, in physicochemically treated wastewater. Furthermore, CW reduced Fe concentrations significantly from 60 to 33 μg/l, Cu from 77 to 40 μg/l, Zr from 5.3 to 1.5 μg/l, Ag from 43 to 14 μg/l, Sn from 54 to 16 μg/l, and Au from 5.8 to 3.2 μg/l. For quantification and assessment of metal accumulation, A. gramineus and C. alternifolius were separately cultivated for 3 months in an experimental CW (length 10 m, width 1.25 m × 2 lanes, depth 0.3 m). The experimental CW showed low removals for most metals, probably because of lower plant density and the shorter HRT than the main CW. Bioconcentration factors (BCFs) of various metals such as Mn, Ni, Cu, Zn, In, Sm, Au, Pb, and Bi for both plants were 10 3–10 4. Generally, the metal with the higher concentration in water presented higher contents in plants. Both emergent plants commonly showed BCFs higher than >10 4 for Fe but lower than <10 3 for Ag and Zr. Regarding accumulated metals, roots generally showed higher metal contents than the rhizomes, stems, or leaves. Translocation factors (TFs) of most metals from roots to rhizomes or leaves of A. gramineus were 10 −2–10 0. Neither Pb nor Zr was detected in leaves of A. gramineus. The TFs of most metals for rhizomes, stems, and leaves of C. alternifolius were, respectively, 10 −1–10 1, 10 −3–10 0 and 10 −2–10 0. No Mn, Ni, Zr, Pb, or Bi was detected in leaves and/or stems, but some were found in roots of C. alternifolius.

Characterization of accumulated precipitates during subsurface iron removal

► Accumulated iron was not found to clog the well or aquifer after 12 years of subsurface iron removal. ► 56–100% of accumulated iron hydroxides were found to be crystalline. ► Subsurface iron removal favoured certain soil layers, either due to hydraulics or mineralogy. ► Other groundwater constituents, such as manganese and arsenic were found to co-accumulate with iron. The principle of subsurface iron removal for drinking water supply is that aerated water is periodically injected into the aquifer through a tube well. On its way into the aquifer, the injected O 2 -rich water oxidizes adsorbed Fe 2+ , creating a subsurface oxidation zone. When groundwater abstraction is resumed, the soluble Fe 2+ is adsorbed and water with reduced Fe concentrations is abstracted for multiple volumes of the injection water. In this article, Fe accumulation deposits in the aquifer near subsurface treatment wells were identified and characterized to assess the sustainability of subsurface iron removal regarding clogging of the aquifer and the potential co-accumulation of other groundwater constituents, such as As. Chemical extraction of soil samples, with Acid-Oxalate and HNO 3 , showed that Fe had accumulated at specific depths near subsurface iron removal wells after 12 years of operation. Whether it was due to preferred flow paths or geochemical mineralogy conditions; subsurface iron removal clearly favoured certain soil layers. The total Fe content increased between 11.5 and 390.8 mmol/kg ds in the affected soil layers, and the accumulated Fe was found to be 56–100% crystalline. These results suggest that precipitated amorphous Fe hydroxides have transformed to Fe hydroxides of higher crystallinity. These crystalline, compact Fe hydroxides have not noticeably clogged the investigated well and/or aquifer between 1996 and 2008. The subsurface iron removal wells even need less frequent rehabilitation, as drawdown increases more slowly than in normal production wells. Other groundwater constituents, such as Mn, As and Sr were found to co-accumulate with Fe. Acid extraction and ESEM–EDX showed that Ca occurred together with Fe and by X-ray Powder Diffraction it was identified as calcite.

Studies on some nutritional quality parameters of organically or conventionally grown wheat

Wheat grain samples were drawn from a field experiment conducted for 2 years at the Indian Agricultural Research Institute, New Delhi, India to study protein, hardness score index, sedimentation value, Zn and Fe concentration in organically and conventionally grown wheat. An aestivum and a durum cultivar were included in the study. Protein concentration in both the cultivars was more in conventionally grown than in organically grown wheat. Grain hardness was not influenced by nutrient management but sedimentation value was higher when wheat was conventionally grown. On the other hand, Zn concentration in both the cultivars was more in organically grown (with farmyard manure) than in conventionally grown wheat. Application of Azotobacter reduced Zn concentration in both the cultivars. The two cultivars, however, differed in respect of Fe concentration in wheat grain. Triticum aestivum cultivar ‘HD 2733’ had significantly more Fe in wheat grain when organically grown compared to that when grown conventionally, while the reverse was true in the case of Triticum durum cultivar ‘PDW 215’. Azotobacter inoculation reduced Fe concentration in wheat in both the cultivars; reduction was more in Azotobacter culture W5.

Disruption ofOsYSL15Leads to Iron Inefficiency in Rice Plants

Uptake and translocation of metal nutrients are essential processes for plant growth. Graminaceous species release phytosiderophores that bind to Fe(3+); these complexes are then transported across the plasma membrane. We have characterized OsYSL15, one of the rice (Oryza sativa) YS1-like (YSL) genes that are strongly induced by iron (Fe) deficiency. The OsYSL15 promoter fusion to beta-glucuronidase showed that it was expressed in all root tissues when Fe was limited. In low-Fe leaves, the promoter became active in all tissues except epidermal cells. This activity was also detected in flowers and seeds. The OsYSL15:green fluorescent protein fusion was localized to the plasma membrane. OsYSL15 functionally complemented yeast strains defective in Fe uptake on media containing Fe(3+)-deoxymugineic acid and Fe(2+)-nicotianamine. Two insertional osysl15 mutants exhibited chlorotic phenotypes under Fe deficiency and had reduced Fe concentrations in their shoots, roots, and seeds. Nitric oxide treatment reversed this chlorosis under Fe-limiting conditions. Overexpression of OsYSL15 increased the Fe concentration in leaves and seeds from transgenic plants. Altogether, these results demonstrate roles for OsYSL15 in Fe uptake and distribution in rice plants.

Iron‐shortage‐induced increase in citric acid content and reduction of cytosolic aconitase activity in Citrus fruit vesicles and calli

Aconitase, which catalyses the conversion of citrate into isocitrate, requires Fe for its activity. The yeast and animal enzyme loses its enzymatic activity under Fe shortage and binds to RNA of genes involved in Fe homeostasis, altering their expression. Thus, the enzyme provides a regulatory link between organic acid metabolism and Fe cellular status. Roots and leaves of Fe-deficient plants show induction in organic acids, especially citrate. Although no RNA-binding activity has been so far demonstrated for the plant aconitase, whether alternations in enzyme activity by Fe could play a role in this induction remain unanswered. This question was investigated in lemon fruit [Citrus limon (L.) Burm var Eureka], characterized by the accumulation of citrate to about 0.3 M in the juice vesicles cells (pulp). Calli and isolated juice vesicles showed two- to three-fold induction in citrate level when subjected to Fe shortage. The mRNA level of aconitase exhibited no changes under reduced Fe concentrations. Analysis of aconitase isozymes demonstrated that out of two aconitase isozymes, typically detected in citrus fruit, only the cytosolic form displayed a reduced activity under low Fe concentrations. Our data support the notion of a limited Fe-availability-induced reduction in cytosolic aconitase, resulting in a slower rate of citrate breakdown and a concomitant increase in citrate levels.