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1.
Abstract

The efficacy of five solutions for extracting sulfate from a peat‐based medium was investigated. Extracting solutions used were 10 mM LiCl, 10 mM KC1, 100 mg/L P, 500 mg/L P, 0.15% CaCl2, or distilled water. Equilibration time affected the amount of sulfate extracted with the use of 100 mg/L P or distilled water extractants. Differences in the amount of sulfate extracted were observed at 0.5‐, 4‐, and 12‐hour equilibration times. Extraction effectiveness increased with the increase of equilibration time, up to a maximum of 4 hours. The concentration of sulfate extracted with all extractants levelled off at the 2‐hour equilibration time. CaCl2 was the most effective solution for the extraction of water‐soluble sulfate. Water‐soluble sulfate plus absorbed sulfate was most efficiently extracted with 500 mg/L P. No relationship was observed between measured sulfate and the pH levels of the extracted solutions.  相似文献   

2.
Bush bean and pea plants grown in a sandy substrate and treated daily with nutrient solutions containing either 50 and 125 pM cadmium (Cd), added as cadmium nitrate [Cd(NO3)2], were analyzed for dry matter production, total Cd content, and extractable Cd. Cadmium depressed dry matter production of both plant species. Bush bean plants accumulated larger amounts of Cd in tissues and displayed lower Cd tolerance than pea plants. The high accumulation of Cd in roots of bush bean does not seem to prevent Cd translocation. Pea plants show a higher exclusion capacity at the root level, suggesting that membrane selectivity rather than apoplastic compartmentation may act as a defence mechanism against Cd toxicity. Gel‐permeation chromatography and voltammetric analyses showed that part of water‐soluble Cd extracted from tissues of pea and bush bean was as free metal ion (Cd2+). In addition, Cd into the nutrient solution induced progressively the synthesis of water‐soluble proteins at low molecular weigth in tissues of both plant specie. In root extracts of pea and bush bean, Cd was also associated with “like‐protein”; fraction with apparent molecular weight >30 KDa.  相似文献   

3.
Abstract

The effect of sewage sludge applications on extractability and uptake by chard and lettuce of soil cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), leaf (Pb), and zinc (Zn) was investigated. Ten different treatments (0, 150, 300, and 500 kg N ha‐1) as mineral fertilizer, and 400, 800, and 1,200 kg N ha‐1 of aerobically and anaerobically‐digested sewage sludges were applied annually to a sandy‐loam soil since 1984. Seven years after the start of the treatments, higher levels of heavy metals were detected in the soil, depending on the type of metal, depth of sampling, type of sludge used, and, especially, rate of application. Following a sequential extraction procedure incorporating 0.1M CaCl2, 0.5M NaOH, and 0.05M Na2EDTA, most of the heavy metals in soil were detected in the Na2EDTA solution and the residual fractions. Large amounts of Cd appeared to be extracted by CaCl2, whereas substantial amounts of Cu and Ni were isolated by NaOH. The effect of treatments on the percentages of the metals found in each fraction depended on the type of metal, sampling depth, sludge used, and application rate. No significant increases were found in the heavy metal contents of chard and lettuce leaves, but some of the treatments resulted in a significant decrease of Cd and Cr levels in lettuce leaves.  相似文献   

4.
Abstract

Calcium (Ca) uptake was studied by immersing the central tip of a trifoliate leaf in various concentrations of 45CaCl2 solutions and under moisture stress conditions during the seed‐filling period of soybean. Beta‐ray gauging and the diurnal leaf temperature variation showed similar characteristics for leaf water status. The activities of 45Ca were significantly higher (p < 0.0001) at 5, 10, 20, and 30 mM concentrations for water stressed and non‐stressed leaves compared with the control. Calcium (45Ca) activities at 5, 10, and 20 mM Ca concentrations between stressed and non‐stressed leaves were not significant, but the difference in their mean values at 30 mM Ca concentration was significant (p = 0.0159). The relationship between 45Ca uptake and Ca concentration was parabolic for both stressed (R2 = 0.77) and non‐stressed (R2 = 0.81) leaves. Autoradiographs indicated Ca movement through the mid‐rib and veins of the tip‐immersed trifoliate leaf but showed no activity in other plant parts. An activity gradient developed between seeds when a pod‐tip was immersed in the radioactive solution.  相似文献   

5.
Abstract

Mobilization of iron (Fe) chelated by humic acids (HA) of low (HA10,000) and high molecular weight (HA100,000) fractions and its uptake by plants were investigated in growth experiments with sunflower seedlings. The iron chelates (labeled with 59Fe) contained in dialysis bags (mw. cutoff=3500) were placed in minus iron Hoagland solutions as the Fe source and at the same time fulvic acid (FA), EDTA, and low and high molecular weight HA fractions were added in the solutions as mobilizators. Characterization of FA, HA10,000, and HA100,000 were performed by infrared spectroscopy and chemical analysis, e.g., total acidity, COOH, and phenolic‐OH content. Roots and leaves were harvested, dried, and ground for Fe activity determination. Iron contents and pH in the nutrient solutions were measured before and after treatments. The supply of Fe to the plants was apparently sufficient, because no Fe deficiency has been detected in the test plants but during the whole absorption period, the pH of the nutrient solution was about 4.5. The Fe contents in leaves indicated that part of the Fe was rapidly transported from roots to leaves. Judging from the Fe contents in leaves, it was assumed that the small size HA10,000 and EDTA were the most efficient in affecting transport of Fe from root to leaf tissue. FA, HA10,000, and especially HA100,000 were unable to penetrate the dialysis bags and, hence, were effective in Fe mobilization only after the Fe, dissociated from the Fe‐HA chelate, has passed the dialysis membrane into the nutrient solutions. In contrast, the small size EDTA was expected to have penetrated the dialysis bags, permitting mobilization of chelated Fe by ligand exchange inside the bags, and transporting the Fe to the roots. The results suggested that the humic substances used in this study were able to form with the Fe3+ ion complexes that maintained the iron available to the sunflower plants. In the chemical form of Fe.L, where L was FA o HA, the iron within the bags or in solution or in the roots free space, was available for exchange reactions with the natural sunflower plant chelators for its transport to the leaves.  相似文献   

6.
Abstract

A method is proposed for determination of hot‐water‐soluble boron in acid soils from western Oregon. The soil sample is boiled in 0.02 M CaCl2, filtered, and B determined using azomethine‐H. Soils extracted in this way yielded extracts with little color in them and the predicted error due to this color was 0.00–0.07 ppm B. The use of charcoal as a decolorizing agent resulted in comparatively high predicted errors.

Inductively‐coupled plasma emission spectroscopic (ICP) analysis of distilled water and 0.02 M CaCl2 extracts indicated that the extractable B level was not affected by the presence of CaCl2. Azomethine‐H yielded comparable values to ICP but the curcumin method tended to give high values for hot‐water‐soluble B.  相似文献   

7.
Cadmium (Cd) uptake by white lupin (Lupinus albus) was studied at low Cd concentrations (0.05nM to 5 μM) in hydroponic solution. Ten 12‐day old seedlings were pretreated in 0.5 mM CaCl2 solution in presence and absence of metabolic inhibitors (DCCD, DNP or NaN3). Cadmium solutions were labelled with carrier free 109CdCl2. Cadmium uptake was measured after a 2 h desorption in unlabelled CdCl2 solution. In the absence of any metabolic inhibitor and at 5 [μM Cd, roots absorbed 235.23 μg Cd/g root dry weight. Over the range of lnM to 5 μM Cd, exchangeable Cd represented approximately 5% of the absorbed fraction, and about 25 % of the total absorbed Cd was adsorbed to the root. Cadmium was passively absorbed to about 30% as observed in the presence of the inhibitor (DCCD). Ative absorption which represented 70% of Cd uptake involved H+‐ATPase carriers. Cadmium absorption was reduced to 30 and 20% in presence of lanthanum (La3+) and zinc (Zn2+), respectively which suggested that calcium (Ca), Cd, and Zn use the same carriers. Cadmium uptake in presence of DNP or NaN3 was approximately 4‐ fold that in control. Data showed presomption for an excretion of Cd out of root cells which could be the expression of a detoxification process limiting cell contamination.  相似文献   

8.
Abstract

Eighteen soils from northwestern Switzerland were used to study the value of seven universal extractants (CaCl2; DB‐DTPA; Mehlich 1, 2, and 3; Morgan‐Wolf; and NH4OAc‐EDTA) for predicting plant available potassium (K) as compared to a bioassay (a modified Neubauer test with winter rye). These extractants were evaluated on the basis of K uptake by the bioassay test and the soil K status. In order to create the sufficiency level of exchangeable K for plant growth, soils were treated with 0, 20, 40, 80, and 160 mg K/kg of soil. The range of K uptake by the bioassay tests was between 89.2 and 403.0 mg/kg of soil for the control pots, and 136.6 to 495.8 for the K treatments with optimal conditions for plant growth. The average amounts of K extracted by the seven universal extractants, in ascending order, were: CaCl2 < Morgan‐Wolf < Mehlich 1 < Mehlich 2 < NH4OAc‐EDTA < Mehlich 3 < DB‐DTPA. The highest simple correlation with K uptake versus the bioassay test was obtained with the DB‐DTPA (r = 0.89) extractant and the lowest with the Mehlich 1 (r = 0.53) extractant. The DP‐DTPA, NH4OAc‐EDTA and Mehlich 3‐K procedures showed an advantage over K procedures based on water soluble and exchangeable K pools in the investigated soils in order to predict the amount of plant‐available K. A simple regression and the Cate‐Nelson graphic method offer the possibility of assessing the soil‐K status using K values obtained by these universal extractants and to calibrate them against K forms as follows: exchangeable, water soluble, and non‐exchangeable.  相似文献   

9.
In this study, complexation extractants ammonium bicarbonate diethylene triamine pentaacetic acid (AB-DTPA), diethylene triamine pentaacetic acid (DTPA), and ethylene diamine tetraacetic acid (EDTA) and mild cation-exchange extractants calcium chloride (CaCl2) and ammonium nitrate (NH4NO3) were used to evaluate the bioavailability of soil cadmium (Cd) to cacao in the field. Among the five extractants, the extractable Cd generally followed the order EDTA > DTPA > AB-DTPA > CaCl2 > NH4NO3. Correlation analysis was done between the extractable Cd in soil and total Cd content of cacao tissues (nibs, shells, leaves, and pods). The Cd extracted by CaCl2 and NH4NO3 was significantly (P < 0.05) correlated with some of the tissues but their Pearson correlation coefficients were weak. In contrast, extractants AB-DTPA, DTPA, and EDTA showed stronger, significant correlations to the Cd concentration in all four tissues. Overall, regression analysis demonstrated that AB-DTPA, DTPA, or EDTA can be used to predict bioavailable Cd in soils for cacao. Of these, AB-DTPA and DTPA both showed the strongest correlations compared to EDTA. However, the ease of preparation and the superior shelf-life of DTPA over AB-DPTA make it the preferred reagent for Cd bioavailability extractions from cacao soils and is currently being used to develop cost-effective soil treatments to reduce bioavailable Cd to cacao plants.  相似文献   

10.
Abstract

Open and closed incubation systems were studied as means of quantifying sulfate fractions in sphagnum peat moss. Sulfate was extracted in the closed system with a 0.15% CaCl2‐H2O or a 500 mg P/L extractant. Sulfate was extracted in the open system with 10 mM KC1, 0.15% , CaCl2‐H2O, or 500 mg P/L extractant. Extractants were quantified by ion chromatography. Phosphate extractant released more sulfate than CaCl2, in the closed system. There was a significant increase over time of sulfate released by the CaCl2 extractant. In the open system, there was no significant difference in release and total amounts leached of sulfate‐S between extractants. The closed system released more sulfate‐S than the open system. Phosphate extractants in both systems mineralized 43% of initial sulfur content  相似文献   

11.
Ethylendiamintetraacetic acid (EDTA) is persistent in the environment. The presence of EDTA in soil may alter the mobility and transport of Zn, Cd and Ni in soils because of the formation of water soluble chelates, thus increasing the potential for metal pollution of natural waters. Mobility of metals is related to their extractability. To investigate metal extractability affected by EDTA, Zn, Cd and Ni were added to Vertisol and Alluvial soil at rates of 50, 2 and 5 mg kg-1, respectively. Both natural and metal amended soils were treated with Na2EDTA at rates of 0; 0.2 and 0.5 mg kg-1. After five months of incubation soil samples were extracted with 0.1 N HCl, 0.005 M DTPA + 0.01 M CaCl2 + 0.1 M TEA (0.005 M Diethylenetriaminepentaacetic acid + 0.01 M Calcium cloride + 0.1 M Triethanolamine) and 1 M Mg(NO3)2, the latter of which extracts the exchangeable from of metald (Zn, Cd and Ni).

According to experiment results, Zn, Cd and Ni in all extraction increased with increasing rates of EDTA in the natural and metal amended soils.  相似文献   

12.
Behaviour of heavy metals in soils. 2. Extraction of mobile heavy metals with CaCl2 and NH4NO3 156 soil samples from arable fields, grassland and forest stands were analysed for the CaCl2? and NH4NO3? extractable contents of Cd, Zn, Mn, Cu and Pb. The average amounts of Cd, Zn, Cu and Pb extracted with CaCl2 are higher compared with NH4NO3 whereas the relation for Mn is vice versa. The proportion of the NH4NO3? extractable contents in percent of the CaCl2? extractable contents of Cd, Zn and Pb decrease with increasing pH, whereas the contents of Mn and Cu increase. Inspite of a differing extraction behaviour of the two salt solutions the CaCl2? and NH4NO3? extractable amounts of Cd, Mn, Zn und Pb are highly correlated and can be converted one into another. The mobile (CaCl2, NH4NO3) proportion of the corresponding total, EDTA and DTPA heavy metal contents is in close relation to the pH of the soils. Using CaCl2 solution the threshold pH values for an increasing mobility decrease in the order Cd > Mn > Zn > Cu > Pb, using NH4NO3 as extractant the order is Mn > Cd > Zn > Cu > Pb. In the case of CaCl2 as extractant soluble chloro-Cd-complexes will be formed so that the Cd mobility in soils will be overestimated in most cases.  相似文献   

13.
Alleviation by calcium (Ca) of inhibition of soybean [Glycine max (L.) Merr. cv. ‘Ransom'] root elongation by hydrogen (H) and aluminum (Al) was evaluated in a vertical split‐root system. Roots extending from a limed and fertilized soil compartment grew for 12 days into a subsurface compartment containing nutrient solution with treatments consisting of factorial combinations of either pH (4.0, 4.6, and 5.5) and Ca (0.2, 2.0, 10, and 20 mM), Al (7.5, 15, and 30 μM) and Ca (2.0,10, and 20 mM) at pH 4.6, or Ca (2, 7, and 12 mM) levels and counter ions (SO4 and Cl) at pH 4.6 and 15 μM Al. Length of tap roots and their laterals increased with solution Ca concentration and pH value, but decreased with increasing Al level. Length of both tap and lateral roots were greater when Ca was supplied as CaSO4 than as CaCl2, but increasing Ca concentration from 2 to 12 mM had a greater effect on alleviating Al toxicity than Ca source. In the absence of Al, relative root length (RRL) of tap and lateral roots among pH and Ca treatments was related to the Ca:H molar activity ratio of solutions (R2≥0.82). Tap and lateral RRL among solutions with variable concentrations of Al and Ca at pH 4.6 were related to both the sum of the predicted activities of monomeric Al (R2≥0.92) and a log‐transformed and valence‐weighted balance between activities of Ca and selected monomeric Al species (R2≥0.95). In solutions with 15 μM Al at pH 4.6, response of tap and lateral RRL to variable concentrations of CaSO4 and CaCl2 were related to predicted molar activity ratios of both Ca:Al3+ (R2≥0.89) and Ca:3 monomeric Al (R2≥0.90), provided that AISO4 and AI(SO4)2 species were excluded from the latter index. In all experiments H and Al inhibited length of lateral roots more than tap roots, and a greater Ca:H or Ca:Al concentration ratio was required in solutions to achieve similar RRL values as tap roots.  相似文献   

14.
《Journal of plant nutrition》2013,36(10-11):2243-2252
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.  相似文献   

15.
Abstract

Cadmium in solution culture at 10‐4 M decreased Mn concentrations in bush beans (Phaseolus vulgaris L. C.V. Improved Tendergreen) at both low and high concentrations of Mn (noncompetitive inhibition). When Mn was decreased, the concentrations of Fe and several other ions were simultaneously increased, particularly in leaves and roots. Toxicity due to the 10‐6 M Cd and the 10‐4 M Mn was additive in the experiment. When barley (Hordeum vulgare L. Atlas57)was grown in amended soil, 15μg Fe as DTPA (diethylene triamine pentaacetic acid) per g soil resulted in increased uptake of Cd and in somewhat greater yield depression for soil pH of 3.9, 6. 0, and 7.6. Acidification of soil without DTPA also increased Cd uptake to high levels with associated yield decrease. The Cd decreased the uptake of Mn and Cu most when CaCO3 had also been added to the soil. When salts were added to soil with Cd before bush beans were grown, KCl (200 μg K/g soil), and equivalent KH2PO4 increased Cd concentrations of leaves while CaSO4 and KCl did so for roots. In bush beans with different levels of Cd and Zn, there were no yield interactions, but some interactions of Cd on Zn concentrations in leaves, stems, and roots at the high Zn level.  相似文献   

16.
Abstract

The effect of two different levels of salinity upon adult plants of Digitalis purpurea has been studied. Seeds of D. purpurea plants were sown in pots of equal size and moistened with deionized water during one year. Afterwards, different treatments with NaCl were initiated, the concentrations being 100 mM and 200 mM NaCl in irrigation water during 63 days. Growth, measured as dry and fresh weight, and soluble protein contents, were lower in stressed plants than in control plants. Monovalent cation analysis showed that in leaves K+ plus Na+ (Total M) values did not change with the different treatments, but that in roots these values increased with the increasing salinity stress. On the other hand, proline levels were higher in stressed plants although the accumulation of this amino acid was not significant In leaves, Cl? levels increased linearly with salinity degree, and the accumulation of this ion was faster than that of Na+, whereas in roots, the Cl? level remained relatively low.

Total cardenolide levels in leaves and roots of the 100 mM NaCl plants were higher than those in 200 mM NaCl and control plants. We infer that moderate salinity conditions lead to raised cardenolide levels, principally in leaves, but the reason for this is not clear.  相似文献   

17.
Abstract

The influence of pH upon the availability of sulfate‐sulfur in sphagnum peat moss was studied. Samples of sphagnum peat moss amended with 0, 1.41, 2.82, 3.81 and 5.64 g/L Ca(OH)2, had pH values of 2.8, 3.7, 4.7, 5.8 and 7.0, respectively. Sulfate was extracted from peat samples with a 0.15% CaCl2.H2O or a 500 mg P/L (as Ca(H2PO4)2.H2O) extractant and quantified with a Dionex QIC ion Chromatograph. Sulfate availability from the CaCl2‐extracted solutions was greatest at pH 4.7 and 5.8, but highest at pH 4.7 only for the P‐extracted solutions, in which no measurable extracted sulfur was found at pH levels greater than 4.7.  相似文献   

18.
Measurement of labile (isotopically exchangeable) pools of metals (E values) in soil is required to assess the size of metal pools potentially available to soil organisms, from both a micronutrient deficiency and metal toxicity viewpoint. In this paper, E values of soil Cu were measured by an isotope dilution technique using different solution extracts – water with and without resin purification, water coupled with Donnan dialysis (free ion determination) and 0.01 m CaCl2. Using these techniques, the isotopic exchangeability of Cu species in water extracts was investigated. The results showed that the specific activity of 64Cu in the water‐soluble fraction was less than in the free metal ion fraction or in the fraction that adsorbed to resin. The isotopically non‐exchangeable Cu in water extracts ranged between 4% and 40% of water‐soluble Cu (16% on average), and appeared to be associated with dispersed colloids. The existence of isotopically non‐exchangeable Cu in water extracts led to overestimation (17.7% on average) of isotopically exchangeable Cu in soils when based on the specific activity in water extracts. The method of isotope dilution coupled with resin extraction is recommended for the determination of isotopically exchangeable Cu in soils when water extracts are used.  相似文献   

19.
Abstract

Nutrient solutions containing three levels of phosphate, nitrate, and chloride were applied to cigar‐wrapper tobacco (Nicotiana tabacum L.) plants growing in sand culture for a period of 18 days. Concentrations of other nutrient elements in the nutrient solutions were held constant and the solutions were applied to pots as needed to maintain favorable moisture conditions for plant growth. Plants were in the two leaf stage when transplanted and were maintained on a single nutrient solution for 38 days before treatments were started. At the end of an eight weeks growing period, plant leaves were harvested and analyzed for Ca, Mg, and Mn. Dry matter yield was significantly (P=0.01) increased when 2 mM/1 of Ca(NO3)2 replaced an equivalent amount of Ca(H2PO4)2 or CaCl2 in the nutrient solution. Nitrate significantly (P=0.05) increased Ca and Mg content and decreased Mn concentration in leaf tissue in comparison to chloride. Calcium and Mg content were significantly (P=0.05) decreased and Mn content of tobacco leaves was increased by phosphate in comparison to nitrate and chloride.  相似文献   

20.
Li  Honghong  Yu  Yong  Chen  Yanhui  Li  Yunyun  Wang  Mingkuang  Wang  Guo 《Journal of Soils and Sediments》2019,19(2):862-871
Purpose

This study focused on the effects and mechanisms of biochar amendment to Cd-contaminated soil on the uptake and translocation of Cd by rice under flooding conditions.

Materials and methods

Pot and batch experiments were conducted using Cd-contaminated soil collected from a field near an ore mining area and a cultivar of Oryza sativa ssp. indica. Biochar derived from rice straw under anaerobic conditions at 500 °C for 2 h was mixed with the soil at the rate of 0, 2.5, and 5%.

Results and discussion

The application of 5% biochar reduced CaCl2-extractable soil Cd by 34% but increased Cd concentration in brown rice by 451%. Biochar amendment decreased water-soluble Fe2+ in soils and formation of Fe plaques on roots and weakened the Fe2+-Cd2+ competition at adsorption sites on the root surface. Biochar increased water-soluble Cd in the soil and consequently Cd uptake by rice roots by releasing water-soluble Cl?. Biochar application also reduced the proportion of cell wall-bound Cd in the root, which caused easier Cd translocation from the cortex to the stele in the root and up to the shoot.

Conclusions

Rice straw biochar (with high concentration of water-soluble Cl?) reduced CaCl2-extractable soil Cd but increased Cd concentration in rice under flooding condition.

  相似文献   

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