Toxic Metals in Soil–Plant Systems,edited by Sheila M. Ross

Water, Air, &; Soil Pollution -     

Remediation of Perfluorooctane Sulfonate in Contaminated Soils by Modified Clay Adsorbent—a Risk-Based Approach

Perfluorooctane sulfonate (PFOS), which has numerous uses besides being an ingredient in the formulation of aqueous film-forming foams, is considered as an emerging pollutant of increasing public health and environmental concern due to recent reports of its worldwide distribution, environmental persistence and bioaccumulation potential. In an attempt to recommend a ‘risk-based’ remediation strategy, this study investigates the removal of PFOS from impacted waters and fixation of PFOS in impacted soils using a novel modified clay adsorbent (MatCARE?, patent number 2009905953). Batch adsorption tests demonstrated a much faster adsorption kinetics (only 60 min to reach equilibrium) and remarkably higher PFOS adsorption capacity (0.09 mmol g^?1) of the MatCARE? compared to a commercial activated carbon (0.07 mmol g^?1). Treatability studies, performed by treating the PFOS-contaminated soils with the MatCARE? (10 % w/w) and then incubating at 25 and 37 °C temperatures maintaining 60 % of the maximum water holding capacity of the soils for a period of a year, demonstrated a negligible release (water extractable) of the contaminant (only 0.5 to 0.6 %). The fixation of PFOS in soils by the new adsorbent was exothermic in nature. Soils with higher clay and organic matter content, but lower pH values, retained PFOS to a much greater extent. A cost analyses confirmed that the MatCARE^TM could be an economically viable option for the ‘risk-based’ remediation of PFOS in contaminated waters and soils.     

Trace Analysis of N-Nitrosamines in Water Using Solid-Phase Microextraction Coupled with Gas Chromatograph–Tandem Mass Spectrometry

A method that utilizes solid-phase microextraction (SPME) coupled with gas chromatography (GC) and chemical ionization tandem mass spectrometry (MS/MS) was developed for analyzing a group of emerging pollutants, N-nitrosamines, in water. The developed analytical method requires a water sample of less than 5 ml and only 1.5 h for complete analysis. The method detection limits for N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine, and N-nitrosodi-n-propylamine were in the range of 3.2 to 3.5 ng/l; for N-nitrosomorpholine, it was 15.2 ng/l. The method was successfully employed to measure the N-nitrosamine concentration at trace levels of nanogram per liter in four water treatment plants (WTPs) and one water distribution system. In the WTPs, only NDMA was detected in the treatment processes. Within the treatment train, NDMA was observed after chlorination. The level of NDMA significantly declined after slow sand filtration due presumably to microbial degradation. The NDMA concentration collected from consumer tap water was about 40% higher on average than that in the finished water. The excellent performance of the SPME/GC/MS/MS method in various water matrices as well as the shorter analysis time and smaller sample volume compared to currently used extraction techniques makes it an alternative means for the analysis of N-nitrosamine in drinking water, wastewater, and laboratory research with small reactors.     

Remediation of Metal Contaminated Soil by Organic Metabolites from Fungi I—Production of Organic Acids

Investigations were made on living strains of fungi in a bioremediation process of three metal (lead) contaminated soils. Three saprotrophic fungi (Aspergillus niger, Penicillium bilaiae, and a Penicillium sp.) were exposed to poor and rich nutrient conditions (no carbon availability or 0.11 M d-glucose, respectively) and metal stress (25 µM lead or contaminated soils) for 5 days. Exudation of low molecular weight organic acids was investigated as a response to the metal and nutrient conditions. Main organic acids identified were oxalic acid (A. niger) and citric acid (P. bilaiae). Exudation rates of oxalate decreased in response to lead exposure, while exudation rates of citrate were less affected. Total production under poor nutrient conditions was low, except for A. niger, for which no significant difference was found between the poor and rich control. Maximum exudation rates were 20 µmol oxalic acid g^?1 biomass h^?1 (A. niger) and 20 µmol citric acid g^?1 biomass h^?1 (P. bilaiae), in the presence of the contaminated soil, but only 5 µmol organic acids g^?1 biomass h^?1, in total, for the Penicillium sp. There was a significant mobilization of metals from the soils in the carbon rich treatments and maximum release of Pb was 12% from the soils after 5 days. This was not sufficient to bring down the remaining concentration to the target level 300 mg kg^?1 from initial levels of 3,800, 1,600, and 370 mg kg^?1in the three soils. Target levels for Ni, Zn, and Cu, were 120, 500, and 200 mg kg^?1, respectively, and were prior to the bioremediation already below these concentrations (except for Cu Soil 1). However, maximum release of Ni, Zn, and Cu was 28%, 35%, and 90%, respectively. The release of metals was related to the production of chelating acids, but also to the pH-decrease. This illustrates the potential to use fungi exudates in bioremediation of contaminated soil. Nonetheless, the extent of the generation of organic acids is depending on several processes and mechanisms that need to be further investigated.     

Soil‐Test Methods for Florida Sands Treated with an Aluminum–Water Treatment Residual and Various Phosphorus Sources

Use of aluminum (Al)–rich water treatment residuals (Al‐WTR) has been suggested as a practice to immobilize excessive phosphorus (P) in Florida soils that could represent an environmental hazard. Fertilizer P requirements can differ in WTR‐amended and unamended soil, so careful selection of soil‐testing methodology is necessary. Acidic extractants can dissolve WTR sorbed P and overestimate plant‐available P. We evaluated the suitability of the Mehlich 1 P (M‐1P) and other agronomic soil‐test procedures in an Al‐WTR‐treated Florida soil. Bahiagrass (paspalum notatum Fluggae), ryegrass (Lolium perenne L.), and a second bahiagrass crop were grown in succession in a Florida topsoil amended with four sources of P at 44 kg P ha^?1 (P‐based rates) and 179 kg PAN ha^?1 [nitrogen (N)–based rates] and three WTR rates (0, 10, and 25 g kg^?1 oven‐dry basis). Both water‐extractable P (WEP) and iron (Fe) strip P (ISP), but not M‐1P, values of soil sampled at planting of each grass were greater in the absence than in the presence of WTR. Total plant P uptake correlated with WEP (r² = 0.82^***) and ISP (r² = 0.75^***), but not M‐1P (r² = 0.34^***). Correlations of the dry‐matter yield, P concentration, and P uptake of the first bahiagrass were also better with WEP and ISP than with M‐1P values. However, regression of plant responses with M‐1P improved after the first crop of bahiagrass. Both WEP and ISP values were better predictors of available soil P than M‐1P in a field study with same four P sources surface applied to established bahiagrass at the same two P rates, with and without WTR. Both WEP and ISP are recommended as predictors of P adequacy in soils treated with WTR, especially for soils recently (< 5 months) treated with Al‐WTR.     

Remediation of organochlorine pesticides (OCPs) contaminated soil by successive hydroxypropyl-β-cyclodextrin and peanut oil enhanced soil washing–nutrient addition: a laboratory evaluation

Purpose

Problems associated with organochlorine pesticides (OCPs)-contaminated sites have received wide attention. To address the associated environmental concerns, innovative ex situ techniques are urgently needed.

Materials and methods

As regards long-term contamination by OCPs in Wujiang region, China, we investigated the feasibility of a cleanup strategy that employed hydroxypropyl-β-cyclodextrin (HPCD) and peanut oil to enhance ex situ soil washing for extracting OCPs, followed by the addition of supplemental nutrients to the residual soil.

Results and discussion

Elevated temperature (50 °C) in combination with ultrasonication (35 kHz, 30 min) at 50 g?L^?1 HPCD and 10 % peanut oil were effective in extracting, and therefore washing, the OCPs in soil. Ninety-three percent of total OCPs, 98 % of dichlorodiphenyltrichloroethanes, 93 % of chlordane as well as 85 % of Mirex were removed from soil after three successive washing cycles. Treating the residual soil with nutrients addition for 12 weeks led to significant increases (p?<?0.05) in the average well color development obtained by the BIOLOG Eco plate assay, Shannon–Weaver index, Simpson index, and EC₅₀ ecotoxicological evaluation compared with the controls. This implied that this cleanup strategy at least partially restored the microbiological functioning of the OCPs-contaminated soil and has the advantage of being an environmental-friendly technology.

Conclusions

The ex situ cleanup strategy through HPCD and peanut oil enhanced soil washing followed by nutrients addition could be effective in remediation of OCPs-contaminated soil.     

Soil Water Retention at Varying Matric Potentials following Repeated Wetting with Modestly Saline‐Sodic Water and Subsequent Air Drying

Abstract

Coal bed natural gas (CBNG) development in the Powder River (PR) Basin produces modestly saline, highly sodic wastewater. This study assessed impacts of wetting four textural groups [0–11%, 12–22%, 23–33%, and >33% clay [(g clay/100 g soil)×100%)] with simulated PR or CBNG water on water retention. Soils received the following treatments with each water quality: a single wetting event, five wetting and drying events, or five wetting and drying events followed by leaching with salt‐free water. Treated samples were then resaturated with the final treatment water and equilibrated to ?10, ?33, ?100, ?500, or ?1,500 kPa. At all potentials, soil water retention increased significantly with increasing clay content. Drought‐prone soils lost water‐holding capacity between saturation and field capacity with repeated wetting and drying, whereas finer textured soils withstood this treatment better and had increased water‐retention capacity at lower matric potentials.     

Underestimation of Available Phosphorus by Resin–Bicarbonate and Olsen Tests in Calcareous Soils treated with Gypsum

In the present study, Olsen [0.5 M sodium bicarbonate (NaHCO₃), pH 8.5] and resin–bicarbonate (HCO₃) tests underestimated available phosphorus (P) in calcareous soils treated with gypsum (CaSO₄). The reaction of CaSO₄ and HCO₃ ^? ion or resin–HCO₃ to form calcium carbonate (CaCO₃) precipitate reduced the strength of the Olsen NaHCO₃ extractant and resin–HCO₃ strip for P extraction. The iron (Fe) oxide–impregnated filter paper (Pi strip) was independent of CaSO₄ influence and thus correctly estimated soil‐available P with respect to plant response to soil‐available P. Two greenhouse experiments were conducted with maize and wheat grown on calcareous soils treated with different rates of CaSO₄. The results confirmed that Olsen and resin–HCO₃ tests should not be used to measure available P or labile P in the P fractionation scheme in the calcareous soils containing significant amounts of gypsum.     

Carbon uptake by a microbial community during 30-day treatment with 13C-glucose of a sandy loam soil fertilized for 20 years with NPK or compost as determined by a GC–C–IRMS analysis of phospholipid fatty acids

To investigate the uptake by the microbial community of easily decomposable exogenous organic C and the proportion of this organic C remaining in soils under long-term fertilization schemes, ¹³C-glucose was supplied to arable soils (aquic inceptisol) following a 20-year (1989–2009) application of compost (CM) or inorganic NPK (NPK), along with a control (no fertilizer). Phospholipid fatty acids (PLFAs) were used as biomarkers for actinobacteria, bacteria and fungi. Gas chromatography–combustion–stable isotope ratio mass spectrometry (GC–C–IRMS) was used to determine the incorporation of ¹³C into individual PLFAs. The concentrations of soil microbial PLFAs significantly (P < 0.05) increased in all three soils after the addition of ¹³C-glucose. Over a 30-day incubation period, the highest PLFA concentrations were on day 7 (control) or day 15 (NPK and CM) for bacteria, and on day 30 for both fungi and actinobacteria. The added ¹³C-glucose was incorporated into bacterial PLFAs first, whilst an increase of ¹³C in fungal and actinobacterial PLFAs was measured on day 7 and 15, respectively. The mean amounts of ¹³C in bacterial, actinobacterial and fungal PLFAs in CM-treated soil during the 30-day incubation period were 0.589, 0.030 and 0.056 μg g⁻¹ soil, respectively, which were significantly (P < 0.05) higher than levels measured in the NPK and control soils. Among the bacterial groups, the amount of ¹³C in Gram-positive (G⁺) bacteria over the entire incubation ranged from 0.326 to 0.440 μg g⁻¹ soil in the CM scheme, which was significantly (P < 0.05) higher than levels detected in the NPK and control regimes. In contrast, ¹³C concentrations in monounsaturated PLFAs (aerobic microorganisms) in the CM-treated soil were 0.030–0.045 μg g⁻¹ soil, which was significantly (P < 0.05) lower than in the NPK schemes. The proportion of glucose-derived ¹³C remaining in soils was ranked as follows: CM (53%) > NPK (41%) > control (28%) after 30 days of incubation. Easily decomposable exogenous organic C was thus more effectively maintained under the CM regime, primarily because, after 20 years, CM had altered the microbial community by reducing the ratio of aerobic to anaerobic microorganisms whilst increasing levels of G⁺ bacteria in soil compared to the control and NPK soils. This study aids our understanding of the transformation and maintenance of easily decomposable organic C in soil over long-term fertilization regimes.     

A Rapid Turbidimetric Potassium Test Modified for Use with the Pressurized Hot‐Water Extraction

Abstract

Colorimetric or turbidimetric quantification of soil potassium (K) coupled with pressurized hot‐water (PHW) extraction could provide an inexpensive alternative to standard methods for small‐scale farmers in developing countries. Two of many methods for K analysis, one using sodium tetraphenylborate and the other using sodium cobaltinitrite, were modified for use with PHW extraction and evaluated for the following requirements: readable on the spectrophotometer, minimal equipment requirement, rapid, simple, and comparable in accuracy to proven methods of K analysis. The sodium tetraphenylborate method was unreliable at low K concentrations, did not relate with K extracted using ammonium acetate and analyzed by atomic absorption (AA), required extract filtration and was too expensive in developing countries. Sodium cobaltinitrite was both simple and inexpensive, and results were consistent and reliable. Test results from 38 arid soils from the western United States support the use of sodium cobaltinitrite as an acceptable procedure for K quantification compared to AA analysis (r² of 0.90, p<0.05). When coupled with PHW, K measured using sodium cobaltinitrite was predictably related with ammonium acetate‐AA measured K (r² of 0.67, p<0.05).     

Evaluation of Water–Nitrogen Schemes for Rice in Iran,Using ORYZA2000 Model

The model ORYZA2000 simulates the growth and development of rice under conditions of potential production and water and nitrogen (N) limitations. Crop simulation models could provide an alternative, less time-consuming, and inexpensive means of determining the optimum crop N and irrigation requirements under varied irrigation and nitrogen conditions. Water productivity (WP) is a concept of partial productivity and denotes the amount or value of product over volume or value of water used. For the evaluated ORYZA2000 model in Iran, a study was carried out in a randomized complete block design between 2005 and 2007, with three replications at the Rice Research Institute of Iran, Rasht. Irrigation management (three regimes) was the main plot and N application (four levels) was the subplot. In this study, simulation modeling was used to quantify water productivity and water balance components of water and nitrogen interactions in rice. Evaluation simulated and measured total aboveground biomass and yield, by adjusted coefficient of correlation, T test of means, and absolute and normalized root mean square errors (RMSE). Results showed that with normalized root mean square errors (RMSE_n) of 5–28%, ORYZA2000 satisfactorily simulated crop biomass and yield that strongly varied among irrigation and nitrogen fertilizer conditions. Yield was simulated with an RMSE of 237–443 kg ha^?1 and a normalized RMSE of 5–11%. Results showed that the significant (28–56%) share of evaporation into evapotranspiration, using the actual yield (measured) and simulated water balance (ORYZA2000), the calculated average WP_ET was significantly lower than the average WP_T: 37%. The average WP_I, WP_I+R, WP_ET, WP_T, and WP_ETQ were 1.4, 1.07, 1.07, 1.57, and 0.82 kg m^?3. Results also showed that irrigation with 8-day intervals and 60 kg N ha^?1, nitrogen level was the optimum irrigation regime and nitrogen level.     

Potassium Release in an Aeric Haplaquept as Influenced by Long-Term Rice–Rice Cropping with Different Rates of Fertilizers and Manuring

Different fractions of potassium (K) and the kinetics of K release as influenced by 21 cycles of rice–rice cropping with different rates of fertilizers and manuring were investigated on an Aeric Haplaquept (kaolinitic Inceptisol) soil profile from Bhubaneswar, India. The neutral 1 N ammonium acetate–extractable K in the surface soil layer (0–15 cm) increased from its initial value of 11.2 mg K kg^?1 to 14.8, 14.2, and 17.5 mg K kg^?1 soil in different treatments. However, the nonexchangeable K content in the surface soil layer dropped considerably to a level of 4.8–20.0 mg K kg^?1 soil. Cumulative nonexchangeable K release after 121 h of extraction with 0.01 M calcium chloride (CaCl₂) was <14 mg K kg^?1. The first-order kinetic model best described the nonexchangeable K release. The decrease in pH and increase in iron (Fe) content indicated the possibilities of K supply to plants through the dissolution of soil minerals.     

Ectogenic Meromixis of Lake Hallst?ttersee, Austria Induced by Waste Water Intrusions from Salt Mining

Lake Hallstättersee is a holomictic alpine lake, which is influenced by salt mining since the middle Bronze Age. Beside the constant saline waste water load, two massive brine spills loaded the lake with additional 16,900 tons sodium chloride (??10,250 tons Cl^?) from 1977 to 1979 and 3,000 tons salt (??1,820 tons Cl^?) in 2005. The effect of waste water intrusions from salt mining on stratification of Lake Hallstättersee was analysed over a period of 40 years. Water density, dissolved oxygen and total phosphorus (TP) concentrations were measured and an exponential model was fitted to describe the wash-out of chloride from Lake Hallstättersee after the brine spills. Furthermore, the time required returning to holomixis and steady chloride content after the second brine spill was estimated. During the whole sampling period the minimum and maximum volume-weighted annual mean chloride concentrations were 23.58 mg/L in 1979 and 3.19 mg/L in 1998. However, the mixing regime of Lake Hallstättersee, as well as the chloride concentrations, varied considerably and exhibited three holomictic and three meromictic periods between 1970 and 2009. Holomictic periods were observed when the yearly density gradient was below 0.06 kg/m³, deepwater oxygen in spring above 4 mg/L and consequently declining TP concentration in the deepest water layer below 60 mg/m³, otherwise meromictic periods were observed. Our study showed that Hallstättersee was 13 years ectogenic meromictic and 27 years holomictic during the study period.     

Uptake of Iron (59Fe) Complexed to Water‐Extractable Humic Substances by Sunflower Leaves

Abstract

A research was carried out to evaluate the leaves' ability to utilize Fe supplied as a complex with water‐extractable humic substances (WEHS) and the long‐distance transport of ⁵⁹Fe applied to sections of fully expanded leaves of intact sunflower (Helianthus annuus L.) plants. Plants were grown in a nutrient solution containing 10 µM Fe(III)‐EDDHA (Fe‐sufficient plants), with the addition of 10 mM NaHCO₃ to induce iron chlorosis (Fe‐deficient plants). Fe(III)‐WEHS could be reduced by sunflower leaf discs at levels comparable to those observed using Fe(III)‐EDTA, regardless of the Fe status. On the other hand, ⁵⁹Fe uptake rate by leaf discs of green and chlorotic plants was significantly lower in Fe‐WEHS‐treated plants, possibly suggesting the effect of light on photochemical reduction of Fe‐EDTA. In the experiments with intact plants, ⁵⁹Fe‐labeled Fe‐WEHS or Fe‐EDTA were applied onto a section of fully expanded leaves. Irrespective of Fe nutritional status, ⁵⁹Fe uptake was significantly higher when the treatment was carried out with Fe‐EDTA. A significant difference was found in the amount of ⁵⁹Fe translocated from treated leaf area between green and chlorotic plants. However, irrespective of the Fe nutritional status, no significant difference was observed in the absolute amount of ⁵⁹Fe translocated to other plant parts when the micronutrient was supplied either as Fe‐EDTA or Fe‐WEHS. Results show that the utilization of Fe complexed to WEHS by sunflower leaves involves an Fe(III) reduction step in the apoplast prior to its uptake by the symplast of leaf cells and that Fe taken up from the Fe‐WEHS complexes can be translocated from fully expanded leaves towards the roots and other parts of the shoot.     

Impacts of Corbicula fluminea on Oxygen Uptake and Nutrient Fluxes across the Sediment–Water Interface

Corbicula fluminea (Asian clam) can assemble in high densities and dominate benthic communities. To evaluate the influence of this clam on sediment oxygen uptake and nutrient fluxes across the sediment–water interface, a microcosm study was conducted using a continuous-flow cultivation system with sediment, lake water, and C. fluminea specimens from Taihu Lake, China. C. fluminea destroyed the initial sediment surface, enhanced O₂ penetration into the sediment partially, and increased the sediment water content, the volume of oxic sediment, and total microbial activity. Sediment O₂ uptake was significantly stimulated by C. fluminea. Linear regression results for O₂ uptake versus clam biomass ranged from 21.9 to 9.47 μmol h^?1 g^?1?DW (dry weight). The release of soluble reactive phosphorus, ammonium, and nitrate from the sediment was also increased by the clams. The increase in the amount of soluble reactive phosphorus and ammonium released into the overlying water was 0.042?~?0.091 and 2.77?~?3.03 μmol h^?1 g^?1?DW, respectively, and this increase was attributed to increased diffusion, enhanced advection between the pore water and the overlying water, and the excretions from C. fluminea. Enhanced nitrification was suggested as the reason for the increase in nitrate release (2.95?~?4.13 μmol h^?1 g^?1?DW) to the overlying water.     

Biomass Production,Forage Quality,and Cation Uptake of Quail Bush,Four‐Wing Saltbush,and Seaside Barley irrigated with Moderately Saline–Sodic Water

Abstract: Beneficial use of water of impaired quality has gained attention globally as society's demand for domestic quality water has increased. Additionally, concerns about the environmental implications of disposal of water of impaired quality have necessitated assessment of alternatives to disposal of such water. The study reported here investigated capacity of Atriplex lentiformis (Torr.) S. Wats. (Quail bush), Atriplex X aptera A. Nels. (pro sp.) (Wytana four‐wing saltbush), and Hordeum marinum Huds. (seaside barley) to produce biomass and crude protein and take up cations when irrigated with moderately saline–sodic water, in the presence of a shallow water table. Water tables were established at 0.38, 0.76, and 1.14 m below the surface in sand‐filled columns. The columns were then planted to the study species. Study plants were irrigated for 224 days; irrigation water was supplied every 7 days equal to water lost to evapotranspiration (ET) plus 100 mL (the volume of water removed in the most previous soil solution sampling). Water representing one of two irrigation sources was used: Powder River (PR) [electrical conductivity (EC) = 0.19 Sm^?1, sodium adsorption ratio (SAR) = 3.5 (mmol_c L^?1)^1/2 ] or coalbed natural gas (CBNG) wastewater [EC = 0.35 Sm^?1, SAR = 10.5 (mmol_c L^?1)^1/2]. Biomass production did not differ significantly between water quality treatments but did differ significantly among species and water table depth within species. Averaged across water quality treatments, Hordeum marinum produced 79% more biomass than A. lentiformis and 122% more biomass than Atriplex X aptera, but contained only 11% crude protein compared to 16% crude protein in A. lentiformis and 14% crude protein in Atriplex X aptera. Atriplex spp. grown in columns with the water table at 0.38 m depth produced more biomass, took up less calcium (Ca²⁺) on a percentage basis [(g Ca²⁺ g^?1 biomass) ×100], and took up more sodium (Na⁺) on a percentage basis than when grown with the water table at a deeper depth. Uptake of cations by Atriplex lentiformis was approximately twice the uptake of cations by Atriplex X aptera and three times that of H. marinum. After 224 days of irrigation, crop growth, and cation uptake, followed by biomass harvest, EC and SAR of shallow groundwater in columns planted to A. lentiformis were less than EC and SAR of shallow ground water in columns planted to either of the other species.     

Desorption and transformation of zinc in a mollisol and its uptake by plants in a rice–wheat rotation fertilized with either zinc-enriched biosludge from molasses or with inorganic zinc

Laboratory and greenhouse investigations were carried out with ⁶⁵Zn-labeled sources to study the kinetics of desorption, transformation, and availability of Zn applied to soil as zinc-enriched biosludge from distillery molasses (ZEMB) or as zinc sulfate heptahydrate (ZSH). Desorption (0.5 to 72 h) of added Zn by the column method followed a biphasic kinetics with an initial (up to 12 h) faster phase followed by a slower desorption phase. The desorption rate coefficient (K) of the latter phase and the amount of Zn desorbed during 12 to 72 h were significantly higher with ZEMB than with ZSH. Sequential extraction of Zn added as ZEMB and ZSH showed that Zn added as ZEMB was present in higher proportion as water soluble + exchangeable, carbonate bound, organically bound, and reducible fractions than Zn applied as ZSH, which showed a higher proportion of residual fraction. Under greenhouse conditions, dry matter yield (35 days) and total Zn uptake by rice fertilized with ZSH applied at 5 kg Zn ha⁻¹ were statistically similar to those of rice treated with 2.5 kg Zn ha⁻¹ supplied as ZEMB. The highest Zn uptake (167.08 μg pot⁻¹) by rice was recorded in the treatment with 5 kg Zn ha⁻¹ as ZEMB. For wheat plants grown after the harvest of rice, significantly higher dry matter yield over control was recorded in the treatment with ZEMB applied at 5 kg Zn ha⁻¹ to rice. Total Zn uptake by wheat was statistically similar for both ZEMB and ZSH treatments at 5 kg Zn ha⁻¹ dose. Both zinc derived from fertilizer and the percent utilization of fertilizer Zn by rice and by the subsequent wheat crop were significantly higher with ZEMB than with ZSH. Patent filed No. 757/MUM/2007 dated 19.04.2007     

Reduction of ferric iron by tumorous crown gall tissue is associated with cells modified by agro‐bacterium tumefaciens

Iron (Fe) uptake and use in plants is genetically controlled and physiological mechanisms such as Fe reduction are induced during Fe‐deficiency stress to make it available. Transfer of DNA into the cell genome by Agrobacterium tumefaciens alters physiological processes and causes undifferentiated growth. Tumor cells in sunflower (Helianthus annus L. cv. Mammoth Russian) show enhanced Fe reduction compared to normal stem tissue in a manner similar to root cells in plants that are genetically switched on or off to manage Fe acquisition. This study addresses whether alterations caused by the DNA transfer from A. tumefaciens result in Fe reduction or whether A. tumefaciens inoculum alone reduces Fe. Reduction of Fe was quantified from A. tumefaciens inoculum and from uninoculated or inoculated sunflower stem tissues daily over a 14‐day period. Neither A. tumefaciens inoculum nor uninoculated stem tissue alone activated massive Fe reduction. High rates of Fe reduction were associated with the proliferation of cells modified by A. tumefaciens. The mechanisms that transformed normal tissue to uncontrolled tumor growth appeared to be linked to active Fe reduction. These modified cells may provide a key to locating and understanding the genetic control of the Fe reduction process in plant cells. Our results suggest a critical role for Fe in development of tumorous tissues and raises the question of whether other tumor cells induce similar mechanisms for Fe acquisition.