Lolium multiflorum uptake of iron supplied as different synthetic chelates

The plant availability of Fe from synthetic chelates has not been examined extensively for plants having the second strategy in iron uptake. Since these plants also excrete chelating agents, competition between natural and synthetic ligands is expected. This research was conducted to study the efficiency of different iron-chelates (Fe-EDTA, Fe-DTPA, Fe-EDDHA and a commercial product, Rexene) inLolium multiflorum iron nutrition. Plants were grown in a greenhouse with hydroponic culture using a buffered nutrient solution at pH 8. Initial iron concentration in the nutrient solution was near 0.5 mgl^–1 and solutions were replaced weekly. In an other Fe-EDTA treatment the same amount of chelate was supplied by four additions during each week.Changes of iron concentration in the nutrient solution, harvestable yield, Fe, Mn, Cu and Zn content in plant tissue and chlorophylllevels in leaves are discussed as parameters to evaluate chelate efficacy. Fe-EDDHA, without inorganic iron in the medium was not as effective as the commercial product Rexene, containing Fe-EDDHA and some extra weakly complex iron, which gave the highest yields. Fe-EDTA applied once a week with fresh nutrient solution was less effective than a four part addition as seen from Chl₁/[Fe] ratios.     

Iron nutrition of a hydroponic strawberry culture (Fragaria vesca L.) supplied with different Fe chelates

Several indexes are used to determine the iron nutritional status of plants, but their effectiveness depends either on the plant growth conditions in natural environments or on the assay conditions. This research was conducted to test different indexes of the iron nutritional status of a hydroponic strawberry culture where treatments mainly differed in the source of the iron applied: Fe-EDTA, Fe-EDDHA and Fe-polyflavonoid. Macro and micronutrient concentrations in the nutrient solutions, leaf and vascular tissues were measured. Fe concentration in the nutrient solution during the course of the experiment was considered in relation to the stability of the different chelates. Both Fe concentration and total Fe content of leaves reflected the effect of the treatments; Fe/Mn ratio was significant as a diagnosis index. Other element ratios as P/Fe and K/Ca are not well related with the iron nutrition symptoms observed. Fe²⁺ concentration measured in leaves was not directly affected by the different chelate treatments.     

Trace elements in the hydrologic cycle of a forest ecosystem

Summary Concentrations of Cu, Fe, Mn, and Zn were measured in bulk atmospheric precipitation, throughfall, stemflow, and soil solutions at 10−, 15−, 25−, and 30-cm depths, in aEucalyptus globulus forest in the Berkeley hills, California, during the 1974–75 wet season after each main storm event. Litter and plant samples were analyzed. There was some similarity in the behavior of Cu, Fe, and Zn, but Mn behaved differently. Mn and Zn are largely deposited on the forest canopy by impaction during dry-deposition episodes, whereas most of the Cu and Fe input occurs in rain. For the hydrologic components measured, concentrations of Cu and Fe increase in the order: precipitation<throughfall<stemflow <soil solutions. For Zn the order is: precipitation<stemflow<throughfall<soil solutions. Concentrations of Cu, Zn, and Fe in the soil solution fluctuate with downward movement of wetting fronts and are negatively correlated with pH. Concentrations of Fe in soil solution are about 10 times greater than those of throughfall and stemflow; the corresponding relative differences for Cu and Zn were much less. Plant uptake of Mn exceeds that of Cu, Zn, and Fe. The increases in Mn concentrations from precipitation to throughfall and stemflow are much greater than those for Cu, Zn, and Fe because precipitation has very low Mn concentrations. The concentration series for Mn is: precipitation<soil solutions<throughfall<stemflow. Concentrations of Mn in the soil solution are negatively correlated with pH. During the dry summer Mn accumulates in the soil, but is quickly flushed by early rains of the wet season.     

Behaviour of iron and manganese chelates in calcareous soils and their effectiveness for plants

Summary The behaviour of the metal chelates Mn-EDTA, Mn-DTPA, Mn-EDDHA, Fe-EDTA, Fe-DTPA and Fe-EDDHA in calcareous soils and their availability to plants were studied. The effectiveness of a metal chelate was shown to depend on its stability, the fixation capacity in the soil and its toxicity to the plant. Incorporation of Fe-DTPA into a framework of silica molecules prevents the fixation of Fe-DTPA in the soil. Fe-DTPA and Fe-EDDHA cause a reduction in the manganese uptake of the plant. The most striking result was the behaviour of Mn-DTPA in calcareous soils. Partial replacement of manganese in the chelate by iron from the soil makes this chelate useful for supplying the plant with both iron and manganese. Mn-DTPA appears to be the ideal type of chelate for the correction of chlorosis in the Netherlands, but unfortunately is not yet commercially available.     

Grain sorghum (Sorghum bicolor Pers.) responses to organic iron on calcareous soils

Effects of Fe-EDDHA (Sequestrene 138), Fe-polyflavonoid (Rayplex), and an experimental iron lignosulfonate on dry matter yields, Fe content, and plant chlorosis of grain sorghum were studied under controlled conditions, using a normal and an Fe-deficient soil (DTPA extract). Application rates of 20, 40, and 80 ppm Fe were employed. Dry matter yields increased due to Fe applications. The lignosulfonate (Fe-LS) produced maximum dry matter yields followed by Fe-EDDHA and the polyflavonoid (Fe-PF) material. At the 80 ppm rate Fe-EDDHA and Fe-PF produced moderate and slight toxic effects, respectively. No toxic effect was noted with the Fe-LS material. Fe-EDDHA was found to be the most effective for correcting iron chlorosis, while the other two sources were similar in this respect. Except for the Fe-LS applied to the normal soil, all other treatments increased Fe content of plant shoots. In the Fe-deficient soil, Fe application lowered the Ca, Mg, Zn, and Mn concentrations in the plants. In the case of the normal soil, concentrations of these elements increased at the 20 ppm rate and underwent no further changes with higher rates. Treatments did not influence K and P concentrations of plants.Additional index words: Micronutrients, Iron compounds.     

Effects of soil acidification on the chemical extractability of Fe,Mn, Zn and Cu and the growth and micronutrient uptake of highbush blueberry plants

Summary The effects of soil acidification and micronutrient addition on levels of extractable Fe, Mn, Zn and Cu in a soil, and on the growth and micronutrient uptake of young highbush blueberry plants (Vaccinium corymbosum L. cv. Blueray) was investigated in a greenhouse study.Levels of 0.05M CaCl₂-extractable Fe, Mn, Zn and Cu increased as the pH was lowered from 7.0 to 3.8. However, the solubility (CaCl₂-extractability) of Fe and Cu was considerably less pH-dependent than that of Mn and Zn. With the exception of HCl-and DTPA-extractable Mn, micronutrients extractable with 0.1M HCl, 0.005M DTPA and 0.04M EDTA were unaffected or raised only slightly as the pH was lowered from 6.0 to 3.8. Quantities of Mn and Zn extractable with CaCl₂ were similar in magnitude to those extractable with HCl, DTPA and EDTA whilst, in contrast, the latter reagents extracted considerably more Cu and Fe than did CaCl₂. A fractionation of soil Zn and Cu revealed that soil acidification resulted in an increase in the CaCl₂- and pyrophosphate-extractable fractions and a smaller decrease in the oxalate-extractable fraction.Plant dry matter production increased consistently when the soil pH was lowered from 7.0 to 4.6 but there was a slight decline in dry matter as the pH was lowered to 3.8. Micronutrient additions had no influence on plant biomass although plant uptake was increased. As the pH was lowered, concentrations of plant Fe first decreased and then increased whilst those of Mn, and to a lesser extent Zn and Cu, increased markedly.     

秦艽药材及其生长土壤中无机元素含量特征及相关性分析

该研究采用原子吸收分光光度法和火焰光度法,测定云南20个种植地的秦艽及其生长土壤中无机元素的含量,探讨药材中无机元素分布特征,并对药材中无机元素含量与土壤中无机元素含量的相关性进行了分析。结果表明：云南秦艽药材无机元素的含量呈现K>Ca>Mg>Fe>Mn>Zn>Cu有规律的分布态势;通过相关性分析、主成分分析和逐步回归分析发现秦艽的特征元素为K、Cu、Ca和Zn;药材中钾含量与土壤中锌,钙与土壤中锰和铜,锰与土壤中钙和镁,铜与土壤中钾和锌元素含量间均分别显著负相关;而药材中镁含量与土壤中钙和镁,铁、铜与土壤中铁元素含量间均呈显著正相关。对秦艽各无机元素含量影响最大的因子是秦艽生长土壤有效钙,有效铁和有效锌其次,最后为有效锰。该研究结果为秦艽道地性成因及适宜栽培区域的选择提供了参考,为秦艽资源合理利用和GAP研究以及从无机元素的角度品评药材品质提供了理论依据。     

Studies on the growth and flowering of a short-day plant,Wolffia microscopica

Summary As found earlier, supply of EDTA was obligatory for both flowering and satisfactory vegetative growth in Wolffia microscopica. It is now shown that the metal affecting growth and flowering is most probably iron. Omission of Fe but not of Cu, Zn, Mn and B from the medium markedly affects vegetative growth. There exists also a strong interaction between EDTA and Fe, one being largely inactive in the absence of the other. When Fe-EDDHA is substituted for Fe-citrate and EDTA in the medium, no great effect is seen in vegetative growth, but flowering takes place even under continuous light. Studies with ⁵⁹Fe show that, in the medium containing Fe-EDDHA, Fe uptake is stimulated several-fold; this is apparently associated with the flowering condition.Abbreviations EDTA ethylenediaminetetraacetic acid - EDDHA ethylenediamine-di-o-hydroxyphenylacetic acid     

Mobilization of iron and other micronutrient cations from a calcareous soil by plant-borne,microbial, and synthetic metal chelators

Mobilization of Fe, Zn, Cu, and Mn by various chelators from a calcareous soil was measured using a simple dialysis tube/complexing resin system. Root exudates from Fe-deficient barley increased the concentrations of all four metals in solution by, on average, a factor of 20, and the addition of complexing resin as a sink for heavy metal cations forced steady state solution concentrations to be reached sooner. Root exudates mobilized increasing amounts of the various micronutrients in the following order: Cu<Fe<Zn<Mn. Phytosiderophores isolated from root exudates of Fe-deficient barley mobilized similar amounts of Cu and Zn but somewhat more Fe and considerably more Mn than crude exudate. The synthetic chelators EDDHA and DTPA showed low specificity in micronutrient mobilization, but the microbial siderophore Desferal was relatively more specific, preferentially mobilizing Fe and Mn. The data indicates that phytosiderophores are capable of increasing the amount of complexed cations in solution. Despite their lack of specificity, phytosiderophores were just as effective as Desferal increasing the availability of Fe. Thus, phytosiderophores, as plant-borne chelators, are certainly of significance for the Fe nutrition of cereals grown in calcareous soils.     

Adsorption of Cu and Zn onto Mn/Fe Oxides and Organic Materials in the Extractable Fractions of River Surficial Sediments

The roles of the extractable components (Mn oxides, Fe oxides, and organic materials) of surficial sediments in controlling metals adsorption were investigated. Cu and Zn adsorptions were conducted before and after the surficial sediments extracted with hydroxylamine hydrochloride, an oxalate solution, and H ₂ O ₂ , respectively. The extraction removed target components with extraction efficiencies from 63 to 98%. Nonlinear regression analyses of Cu and Zn adsorptions based on the assumption of additive Langmuir adsorption isotherm were employed to estimate the relative contributions of sediment components to Cu and Zn adsorptions. The results indicate that the greatest contribution to total Cu and Zn adsorption to the surficial sediments on a molar basis was from Mn oxides in the extractable fractions. Both Cu and Zn adsorption capacities of Mn oxides exceeded those of Fe oxides by approximately one order of magnitude, fewer roles were attributed to the adsorption of organic material (OM), and the estimated contribution of the residual fraction to total Cu and Zn adsorption was insignificant. These information implied that the roles of metal oxides (Fe and Mn oxides) in the extractable form of the surficial sediments, especially Mn oxides, was the most important component in controlling heavy metal transportation in aquatic environments.     

The effect of Fe-EDDHA and of ascorbic acid on in vitro rooting of the peach rootstock GF-677 explants

The objective of this research was to study the effect of the chelated form of the iron salt of ethylenediamine di-o-hydroxyphenylacetic acid (Fe-EDDHA) (6% Fe) on in vitro rooting of the rootstock GF-677. The iron salt of ethylenediamine tetraacetic acid (Fe-EDTA) (12% Fe) of the MS basic medium was replaced by Fe-EDDHA, which was applied in three concentrations: 93.5, 187.0 and 280 mg l⁻¹ (5.6, 11.2 and 16.8 mg l⁻¹ Fe, respectively). For each treatment of Fe-EDDHA, the effect of ascorbic acid added in four concentrations (0, 0.1, 1.0 and 10 mg l⁻¹) was studied. After 4 weeks of culture, the explants growing on the medium with 280 mg l⁻¹ Fe-EDDHA gave the best rooting results. Regarding ascorbic acid, no clear stimulating effect on rooting was found.     

Influence of washing on elemental analysis of leaves of fieldgrown crop plants

Summary Information is limited on soil contamination of leaves from field-grown row crops, especially with respect to aluminum (Al) analyses. The objective of this study was to determine the influence of washing leaf samples with either deionized water or detergent solution on elemental analyses for several agronomic crop plants. The crop plants sampled were corn (Zea mays L.), soybean (Glycine max L. Merr.), grain sorghum (Sorghum bicolor L. Moench), and wheat (Triticum aestivum L.). The crops were grown on a range of soil types, soil pH values, and tillage practices. Samples of upper leaves and lower leaves were collected separately. The samples were either not washed, washed with deionized water, or washed with detergent solution. After drying, grinding, and digesting, the samples were analyzed for Al, nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu). For all crop plants and conditions studied, there was no effect on measured N, P, K, Ca, Mg, Mn, Zn, or Cu concentrations, but measured Al and Fe concentrations were influenced by washing. In general, washing had a greater effect on Al analyses than on Fe analyses. Soybean samples were most affected by washing, while wheat samples seemed to be least affected. The results reflected greater contamination of lower leaves than upper leaves. Decontamination procedures appear necessary prior to Al and Fe analyses of field-grown crop plants.     

Microelement composition of plants grown with low to high levels of sulfur applied to calcareous soil in a glasshouse

Summary PI54619-5-1 soybeans (Glycine max L.), which are very susceptible to Fe deficiency, were grown for 24 days in calcareous (10%) Hacienda loam soil with different levels of S each with and without 2 ppm Fe added as FeEDDHA (ferric ethylenediamine di (o-hydroxyphenylacetic acid). The S application rates ranged from sufficient to neutralize about 15% to more than all of the CaCO₃ present if the S were all oxidized. The soil pH values at harvest time ranged from 7.4 to 6.0. The highest S rate was 10% by weight of soil and it overcame Fe deficiency without FeEDDHA. The S treatments resulted in increased concentrations of Fe and other metals in leaves, but the FeEDDHA treatments increased yields more than did S. At the lower levels of S, the effects of S and FeEDDHA on Fe concentrations in leaves were additive, but not at the highest level of S. The FeEDDHA overcame much of the effect that S had on increasing Mn concentrations in leaves. It had a similar effect, particularly at the low S levels, on Zn, Cu, Al, B, and Ni concentrations in leaves. A level of S sufficient to neutralize only 15% of the CaCO₃ of the soil increased leaf concentrations of Fe, Mn, Zn, Cu, Al, B, Ni, Si, and P. The effect for Zn, Cu, and Al appreared maximum at this level. A combination of the1/2% S and the FeEDDHA resulted in the most favorable micronutrient balance. Bush beans (Phaseolus vulgaris L. var. Improved Tendergreen) grown in calcareous soil with S insufficient to neutralize all the CaCO₃ had increased Mn, Ni, and Mo and decreased Ba levels in leaves. CaSO₄ as a source of S did not have the same effects as elemental S.     

Application of chelator-buffered nutrient solution technique in studies on zinc nutrition in rice plant (Oryza sativa L.)

It has been difficult to impose different degrees of Zn deficiency on Poaceae species in nutrient solution because most chelators which would control Zn to low activities also bind Fe³⁺ so strongly that Poaceae species cannot obtain adequate Fe. Recently, a method has been developed to provide buffered Fe²⁺ at levels adequate for rice using Ferrozine (FZ), and use of other chelators to buffer the other micronutrient cations. The use of Fe²⁺ buffered with FZ in nutrient solutions in which Zn is buffered with HEDTA or DTPA was evaluated for study of Zn deficiency in rice compared to a conventional nutrient solution technique. The results showed that growth of rice plants in FZ+HEDTA-buffered nutrient solution was similar to that in the conventional nutrient solution. Severe zinc deficiency symptoms were observed in 28-day-old rice seedlings cultured with HEDTA-buffered nutrient solution at Zn²⁺ activities < 10^-10.6 M. With increasing free Zn²⁺ activities, concentrations of Zn, Fe, Cu, and Mn in shoots and roots were quite similar for the FZ+HEDTA-buffered nutrient solution and the conventional nutrient solution techniques. The percentages of water soluble Zn, Fe, Cu and Mn in shoots with HEDTA-buffered nutrient solution were also similar to those with the conventional solution. However, with DTPA-buffered nutrient solution, the rice seedlings suffered severe Fe deficiency; adding more FeFZ₃ corrected the Fe-chlorosis but shifted microelement buffering. Further, much higher total Zn concentrations are required to provide adequate Zn²⁺ in DTPA-buffered solutions, and the contents of Mn and Cu in shoots and roots cultured with DTPA-buffered solutions were much higher than those with the conventional or HEDTA-buffered solutions. In conclusion, DTPA-buffered nutrient solutions are not suitable but the FZ/HEDTA-buffered nutrient solution technique can be used to evaluate genotypic differences in zinc efficiency in rice.     

Fe-EDDHA Promotes Rooting of Rootstock GF-677 (Prunus amygdalus × P. persica) Explants in vitro

The effect of organic (Fe-EDTA and Fe-EDDHA) and inorganic (FeCl₃) iron substances on rooting of the rootstock GF-677 (Prunus amygdalus × Prunus persica) in vitro was studied. Full rooting (100 %) was observed in explants nourished with Fe-EDDHA, while less rooting was found in the absence of iron or in the presence of FeCl₃. On the contrary, no root formation was observed in explants nourished with Fe-EDTA, which showed extremely lower chlorophyll and high iron contents at the end of the experiment. This revised version was published online in July 2006 with corrections to the Cover Date.     

Chelate behaviour in saline-alkaline soil conditions

Summary A spectrophotometric method was used to study the effect of pH and competing ions (Ca, Mg, Na) on the stability of Fe- and Cu-chelates of EDTA, DTPA and EDDHA. The measured stability was compared with the calculated stability-pH diagrams. A favourable agreement with the values of the formation constants was observed. Laboratory and pot experiments were carried out by adding these chelates to saline-alkaline soil and the extractable fractions of trace elements in soil and their uptake by barley were evaluated. Availability and uptake of Fe and Cu significantly increased, with different magnitude, by chelate application. The influence on Mn and Zn was variable. The most effective chelating agents, as deduced from uptake were: EDDHA for Fe, Cu and Mn; and EDTA for Zn.Radiobiological and Physical chemistry, Faculty of Agricultural Sciences, Ghent Belgium     

Increased tolerance to the root-lesion nematode Pratylenchus vulnus in mycorrhizal micropropagated BA-29 quince rootstock

The interaction between Glomus intraradices and the root-lesion nematode Pratylenchus vulnus was studied on micropropagated BA-29 quince rootstock during one growing season. Inoculation with G. intraradices significantly increased growth of plants in low P soil and was more effective than P fertilization at increasing top-plant development. In the presence of the nematode, mycorrhizal plants achieved higher values in all growth parameters measured. P. vulnus caused a significant decrease in the percentage of root length colonized by G. intraradices and fewer internal vesicles were formed within the host roots. Enhanced root mass production accounted for the twofold increase in final nematode population recovered from plants with combined inoculations of pathogen and symbiont. Low levels were found of Al, Fe, Mn and Zn in nonmycorrhizal nematode-infected plants in low P soil. G. intraradices-inoculated plants reached the highest foliar levels of N, Ca, Mg, Mn, Cu and Zn. Mycorrhizal plants infected with P. vulnus maintained normal to high levels of Mn, Cu, and Zn. Inoculation with G. intraradices favours quince growth and confers protection against P. vulnus by improving plant nutrition.     

Acquisition of Cu, Zn, Mn and Fe by mycorrhizal maize (Zea mays L.) grown in soil at different P and micronutrient levels

Sustainability of soil-plant systems requires, among other things, good development and function of mycorrhizal symbioses. The effects of P and micronutrient levels on development of an arbuscular mycorrhizal fungus (AMF) and uptake of Zn, Cu, Mn and Fe by maize (Zea mays L.) were studied. A pot experiment with maize either inoculated or not with Glomus intraradices was conducted in a sand:soil (3 :1) mix (pH 6.5) in a greenhouse. Our goal was to evaluate the contribution of mycorrhizae to uptake of Cu, Zn, Mn and Fe by maize as influenced by soil P and micronutrient levels. Two levels of P (10 and 40 mg kg⁻¹ soil) and three levels of a micronutrient mixture: 0, 1X and 2X (1X contained, in mg kg⁻¹ soil, 4.2 Fe, 1.2 Mn, 0.24 Zn, 0.06 Cu, 0.78 B and 0.036 Mo), were applied to pots. There were more extraradical hyphae at the low P level than at the high P level when no micronutrients were added to the soil. Root inoculation with mycorrhiza and application of micronutrients increased shoot biomass. Total Zn content in shoots was higher in mycorrhizal than non-mycorrhizal plants grown in soils with low P and low or no micronutrient addition. Total Cu content in shoots was increased by mycorrhizal colonization when no micronutrients were added. Mycorrhizal plants had lower Mn contents than non-mycorrhizal plants only at the highest soil micronutrient level. AMF increased total shoot Fe content when no micronutrients were added, but decreased shoot Fe when plants were grown at the high level of micronutrient addition. The effects of G. intraradices on Zn, Cu, Mn, and Fe uptake varied with micronutrient and P levels added to soil. Accepted: 27 December 1999     

Arbuscular mycorrhizal contribution to heavy metal uptake by maize (Zea mays L.) in pot culture with contaminated soil

In two pot-culture experiments with maize in a silty loam (P2 soil) contaminated by atmospheric deposition from a metal smelter, root colonization with indigenous or introduced arbuscular mycorrhizal (AM) fungi and their influence on plant metal uptake (Cd, Zn, Cu, Pb, Mn) were investigated. Soil was -irradiated for the nonmycorrhizal control. In experiment 1, nonirradiated soil provided the mycorrhizal treatment, whereas in experiment 2 the irradiated soil was inoculated with spores of a fungal culture from P2 soil or a laboratory reference culture, Glomus mosseae. Light intensity was considerably higher in experiment 2 and resulted in a fourfold higher shoot and tenfold higher root biomass. Under the conditions of experiment 1, biomass was significantly higher and Cd, Cu, Zn and Mn concentrations significantly lower in the mycorrhizal plants than in the nonmycorrhizal plants, suggesting a protection against metal toxicity. In contrast, in experiment 2, biomass did not differ between treatments and only Cu root concentration was decreased with G. mosseae-inoculated plants, whereas Cu shoot concentration was significantly increased with the indigenous P2 fungal culture. The latter achieved a significantly higher root colonization than G. mosseae (31.7 and 19.1%, respectively) suggesting its higher metal tolerance. Zn shoot concentration was higher in both mycorrhizal treatments and Pb concentrations, particularly in the roots, also tended to increase with mycorrhizal colonization. Cd concentrations were not altered between treatments. Cu and Zn, but not Pb and Cd root-shoot translocation increased with mycorrhizal colonization. The results show that the influence of AM on plant metal uptake depends on plant growth conditions, on the fungal partner and on the metal, and cannot be generalized. It is suggested that metal-tolerant mycorrhizal inoculants might be considered for soil reclamation, since under adverse conditions AM may be more important for plant metal resistance. Under the optimized conditions of normal agricultural practice, however, AM colonization even may increase plant metal absorption from polluted soils.     

Effects of ionic and complexed metal concentrations on plant uptake of cadmium and micronutrient metals from solution

Summary Uptake of Cd and micronutrient metals by intact tomato plants (Lycopersicon esculentum, cv. Wisconsin-55) from solution cultures was investigated by establishing four levels of Cd-ion activity in the presence or absence of a metal-complexing agent (±EDTA). Activity ratios of Cd, Cu, Mn, Ni, and Zn were controlled with chelating resin while activity ratios of K, Ca, and Mg were controlled with a strong-acid cation-exchange resin. Hydrogen ion activity was controlled with a weak-acid cation-exchange resin and P activity by a cation-exchange resin containing adsorbed polynuclear hydroxy-Al. The concentrations of all nutrients and Cd were maintained at concentrations similar to those occuring in solutions of sludge-amended soils. The EDTA treatments increased the concentrations of Cu and Ni in hydroponic solution by approximately four orders of magnitude, Zn by two orders of magnitude, Cd by a factor of 50, Mn by a factor of 2.4, and Fe by a factor of 1.6 Neither the Cd nor the EDTA treatments affected plant yield, and Cd treatments did not significantly affect uptake of other elements. EDTA treatments inhibited Fe uptake, enhanced Cu uptake, and had little effect on the uptake of Cd, Zn, and Mn. Accumulation of Cd, Zn, Mn, and Cu in plant shoots appears to be related to their respective ionic activities rather than their concentrations in hydroponic solution. Research supported by the College of Agricultural and Life Sciences, University of Wisconsin-Madison and by the United States Environmental Protection Agency through Grant CR807270010.