Cadmium induced alterations in the intestinal absorption of glucose and fructose in a freshwater cat fish,Heteropneustes fossilis

The effect of four concentrations (1.0, 0.1, 0.01, and 0.001 mM) of Cd on the rate of absorption of two sugars, glucose and fructose by the intestine of the fresh water cat fish, Heteropneustes fossilis has been studied after 1 h at 23 °C. Intestinal glucose and fructose transport was also assessed in fish exposed to a sublettral concentration (0.0023 mM) of Cd in the ambient water for 15 and 30 days. Control fish showed no marked difference in the rates of absorption of glucose and fructose. All four concentrations of Cd decreased the rate of transport of glucose and fructose significantly. Among the two sugars, decrease in the rate of transport of fructose was more marked than glucose. In fish exposed to Cd in the ambient water, reduction of glucose and fructose absorption was greater after 30 days of exposure than after 15 days.     

Mercuric chloride induced alterations in the intestinal transport of glucose and fructose in the fresh water murrel Channa punctatus

The effect of five concentrations of mercuric chloride (10 mM, 5 mM, 1 mM, 0.5 mM, and 0.l mM) on the uptake of glucose and fructose from the intestine of the fresh water murrel Channa punctatus after 15, 30 and 60 min was studied. Intestinal glucose and fructose transport was also assessed in fish exposed to a sublethal concentration (3 μg l^?1) of mercuric chloride for 10 and 30 days. The results show that the uptake of glucose and fructose from the intestine was reduced by all five concentrations of mercuric chloride. Maximum reduction was observed after 60 min of exposure to 10 mM mercuric chloride. The rate of absorption of glucose and fructose increased with time in controls and in all concentrations of mercury except the highest concentration (10 mM) where the rate of absorption decreased gradually. The reduction in the rate of absorption of the two sugars was not dependent on the concentration of mercury in the instilled medium. In fish exposed to mercuric chloride in laboratory media, the reduction of glucose and fructose absorption was greater after 30 days of exposure than after 10 days.     

Degradation of Sevin by soil microorganisms

Microorganisms capable of transforming the pesticide 1-naphthyl N-methyl-carbamate (Sevin) were isolated from soil. Three isolates were able to accelerate the hydrolysis of Sevin to 1-naphthol. Several unidentified intermediates were separated by thin-layer chromatography and also by following the decomposition of Sevin-methyl-¹⁴C. Since 1-naphthol is a biological as well as a chemical decomposition product of Sevin, its transformation by the isolated microbes was also studied. A fungus, identified as Fusarium solani, altered 1-naphthol rapidly. Whereas one strain of bacterium degraded the hydrolysis product gradually, another strain accumulated it under certain conditions. Mixed cultures of the investigated microbes were more effective in transforming Sevin than pure cultures, and this phenomenon was also observed with 1-naphthol as substrate with the exception of one bacterial strain.     

Signaling by glutamate dehydrogenase in response to pesticide treatment and nitrogen fertilization of peanut (Arachis hypogaea L.).

The responses of glutamate dehydrogenase (GDH) to NH(4)(+) and herbicides offer a new approach for probing the effects of NH(4)(+)-pesticide interactions at the whole-plant level. Although pesticides and fertilizers have greatly enhanced food production, their combined biochemical effects are not known in detail. Peanut plants were treated with different rates of Basagran (3-(1-methylethyl)-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide), Bravo 720 (tetrachloroiso-phthalonitrile), and Sevin XLR Plus (1-naphthyl N-methylcarbamate), with and without 25 mM NH(4)Cl fertilization. Isoelectric focusing, followed by native 7.5% polyacrylamide gel electrophoresis (PAGE) fractionated the peanut seed GDH fully to its isoenzyme population patterns. The pesticide treatments induced positive skewing of the GDH isoenzymes, but NH(4)Cl-pesticide cotreatments induced a negatively skewed distribution. Basagran, Sevin, and Bravo increased the amination activities of GDH from 30.0 +/- 2.8 units in the control assay to 479.0 +/- 20.7, 63.0 +/- 5.8, and 35.2 +/- 2.2 units, respectively, therefore indicating a direct GDH-pesticide interaction. Neither the NH(4)(+) nor the pesticides increased the peanut seed protein yields above the threshold of 3.8 +/- 0.7 g per pot. But in the GDH combination of the signals from a pesticide and NH(4)(+), at least 70% of the pesticide signal was overridden by NH(4)(+) with concomitant increases in peanut seed protein yields to 7.0 +/- 1.8 g per pot. Basagran, Sevin, and Bravo possess different pesticidal properties, but their effects on GDH activity were related in the decreasing order of their nucleophilicity, viz. Basagran > Sevin > Bravo.     

Physiological and Genetic Responses to Pesticide Mixture Treatment of Veronica beccabunga

The effects of a five-pesticide mixture on pesticide accumulation, phytohormone levels (indole-3-acetic acid, gibberellic acid, jasmonic acid, and salicylic acid), pigment contents (total chlorophyll and carotenoid), antioxidant enzyme (catalase and guaiacol peroxidase) activities, lipid peroxidation product (malondialdehyde), and DNA profiles were investigated in the leaves of Veronica beccabunga. Laboratory-acclimatized plants were treated with a mix of five pesticides (atrazine, disulfoton, chlorpyrifos, metalaxyl, and ethion) in doses of 50?ppt, 1?ppb, 100?ppb, and 1?ppm for 1, 3, and 6?days. The accumulation of each pesticide, from highest to lowest, was as follows: chlorpyrifos, atrazine, metalaxyl, disulfoton, and ethion. The amounts of total chlorophyll and protein decreased with increased pesticide concentration. Antioxidant enzyme activities and malondialdehyde amount increased linearly with increasing pesticide exposure. However, the highest pesticide concentration caused decreases in guaiacol peroxidase (POD) activity and malondialdehyde (MDA) content at all treatment times. Both jasmonic and salicylic acid levels increased with pesticide exposure and decreased gradually after. It was also determined that application of the pesticide mixture affected the DNA profiles of V. beccabunga. The most band changes were detected on the sixth day of treatment.     

Historical distribution of DDT residues in pond sediments in an intensive agricultural watershed in the Yangtze-Huaihe region,China

Purpose

The extensive use of chemical pesticides on farmlands during the last several decades in China has led to a rapid deterioration of environmental water quality in recent years. The aims of this study were to: reconstruct the history of pesticide residues, determine the input load and residual load of dichlorodiphenyltrichloroethane (DDT) pesticides, and assess the risk of pesticide residues to aquatic ecosystem and human health.

Materials and methods

Caesium-137 was used to date sediment cores collected from ponds representing four land use types of an agricultural watershed with high-yield grain production and characterized by multipond systems in the Yangtze-Huaihe region of China. These ponds were selected to establish the historic pattern of DDT pesticide residues.

Results and discussion

(1) The mean total concentration of DDT residues including p,?p?′-dichlorodiphenyldichloroethylene (p,p′-DDE), p,?p?′-dichlorodiphenyldichloroethane ( p,p′-DDD), o,p′-DDT, and p,p′-DDT in sediment in the watershed was 82 μg kg^?1, ranging from under the detection limit to 457 μg kg^?1, which was mostly contributed by p,?p′-DDE (57 μg kg^?1 on average). Spatially, total concentrations of DDT residues in farmland pond sediment were the highest, reaching as high as 457 μg kg^?1. Temporally, an inflection point appeared in the 1970s, prior to which DDT contents increased with time, after which concentrations showed a decreasing trend. (2) In total, 323 kg DDT pesticide was applied to the Liuchahe Watershed since 1955. The total retention of four DDT residues in the multipond system was 14 kg (～4 % of the input), and most DDT pesticide was degraded to p,?p?′-DDE. (3) More than 80 % of sediment DDT residues exceeded their interim freshwater sediment quality guidelines, and the percentages of DDT,DDD, and DDE residues exceeding probable effect limit (PEL) values were 57, 29, and 70 %, respectively, which indicated a moderate to high ecological risk of DDT in this watershed.

Conclusions

Our results clearly reveal that the extensive use of pesticides has resulted in significant pesticide residual pollution in this watershed, which could severely deteriorate water quality and threaten aquatic ecosystem and human health in the watershed and, thus, remain a cause for concern.     

Degradation of pesticides in nursery recycling pond waters

Recycling or collection ponds are often used in outdoor container nursery production to capture and recycle runoff water and fertilizers. Waters in recycling ponds generally have high concentrations of nutrients, pesticides, and dissolved organic matter, as well as elevated salinity and turbidity. Little is known about pesticide degradation behavior in the unique environment of nursery recycling ponds. In this study, degradation of four commonly used pesticides diazinon, chlorpyrifos, chlorothalonil, and pendimethalin in waters from two nursery recycling ponds was investigated at an initial pesticide concentration of 50 microg/L. Results showed that the persistence of diazinon and chlorpyrifos appeared to be prolonged in recycling pond waters as compared to surface streamwaters, possibly due to decreased contribution from biotic transformation, while degradation of chlorothalonil and pendimethalin was enhanced. Activation energies of biotic degradation of all four pesticides were lower than abiotic degradation, indicating that microbial transformation was less affected by temperature than chemical transformation. Overall, the pesticide degradation capacity of recycling ponds was better buffered against temperature changes than that of surface streamwaters.     

The potential application of the endophyte Phomopsis liquidambari to the ecological remediation of long-term cropping soil

A broad-spectrum endophyte, Phomopsis liquidambari, was used as a microbial agent to determine the effects of rapid litter decomposition on soil phenolic compounds dynamics, the soil microbial community balance and plant growth. The litter decomposition ratio was closely correlated with lignin degradation. The soil phenol concentration increased with the acceleration of litter decomposition after the first 30 days and later decreased to below the initial level. Based on denaturing gradient gel electrophoresis (DGGE) analysis, soil bacteria, especially gram-negative bacteria that have the potential to degrade aromatic compounds, were found in high abundance when the soil phenol concentration was high. When the phenolic concentration decreased, soil fungi increased in abundance. With fungal application, seed germination significantly increased to 69.87% and seedling growth was enhanced. Rapid litter decomposition by Pho. liquidambari initially led to higher releases of phenolic allelochemicals, which led to the enrichment of soil gram-negative bacteria. In addition, increased soil nutrients and temporarily higher concentrations of phenolics from litter decomposition strengthen seedling growth, suggesting that the endophytic fungus Pho. liquidambari is a suitable candidate for remediation of long-term cropping soil.     

The effect of ph on fungitoxic interactions between a solvent and pesticide

The effect of pH on interactions between combinations of the solvent acetone and the pesticide captan was determined using the fungiPythium ultimum, Sclerotinia homeocarpa, andPestalotia sp.. Seven concentrations of the solvent acetone, ranging from 0.1 to 3.0 % (v/v), were interacted with four concentrations of the fungicide captan, ranging from 1.0 to 10.0 ppm (mg L^?1). This interaction procedure was repeated at pH 4.5, 5.5, 6.5, and 7.5, using a temperature of 30 °C. Acetone and captan interacted synergistically towardsP. ultimum andS. homeocarpa, and antagonistically towardsPestalotia sp., regardless of the pH. However, the solvent concentration at which synergism or antagonism was first observed usually decreased as pH increased. The actual pH response obtained was dependent upon both the captan level and culture used. As pH increased from 4.5 to 7.5, the toxicity of captan decreased by up to 40% withS. homeocarpa andPestalotia sp., and 80% withP. ultimum. WithS. homeocarpa andPestalotia sp., the magnitude of synergism or antagonism increased as the captan concentration was raised from 1.0 or 2.5 ppm up to 7.5 or 10.0 ppm. With P. ultimum, the degree of synergism decreased at pH 4.5 and 5.5, but increased at pH 6.5 and 7.5, as the captan concentration was raised from 2.5 to 10.0 ppm. The lowest interaction magnitudes were recorded at pH 4.5 forP. ultimum, but was variable for the other cultures. The greatest interaction magnitudes were obtained at pH 4.5 forS. homeocarpa, 5.5 forPestalotia sp., and 6.5 or 7.5 forP. ultimum.     

Metabolic changes in the snake head fish Channa punctatus chronically exposed to endosulfan

The chronic toxic effects of a commonly used pesticide endosulfan on the carbohydrate metabolism of the fresh water telcost fish Channa punctatus were investigated. The fish were exposed to a sub-lethal concentration (0.2 μg l^?1) for 15, 30, and 60 days. The levels of glucose, total plasma proteins, lactic acid and haemoglobin in the blood, glycogen and lactic acid contents of liver and muscles were also measured. Alterations in the activities of hexokinase, lactate dehydrogenase and pyruvate dehydrogenase in the glycolytic pathway, and succinate dehydrogenase in the citric acid cycle were examined in the liver, kidney, intestine, brain, gills and muscles. The results showed that 30 and 60 days of exposure produced more significant changes in different parameters in comparison to 15 days. There was a decrease in blood glucose and total plasma proteins but lactic acid and haemoglobin levels were higher in endosulfan exposed fish than in control fish. Glycogen and lactic acid contents of the liver and muscles were depleted. The activity of hexokinase in liver, kidney and intestine was inhibited after 60 days of exposure but in muscles the enzyme activity was elevated. Glucose-6-phosphatasc was inhibited in all the tissues. Lactate dehydrogenase, pyruvate dehydrogenase and succinate dehydrogenase activities decreased in the liver, kidney, brain and gills after 30 and 60 days of exposure. In the muscles, the activities of lactate dehydrogenase and pyruvate dehydrogenase were elevated while succinate dehydrogenase was inhibited. The study showed that formation of glycogen and its breakdown were impaired in the liver. In the muscles, the rate of glycolysis increased probably due to pesticide induced muscular excitment.     

Bioaccessibility of Trace Metals in Sediment, Macroalga and Antifouling Paint to the Wild Mute Swan, Cygnus olor

The bioaccessibilities of trace metals (Cd, Cr, Cu, Ni, Pb, Zn) in eelgrass, sediment and preparations thereof with and without antifouling paint particles have been assessed by undertaken a physiologically based extraction test (W-PBET) designed to mimic the chemistry of the gizzard and intestine of the mute swan, Cygnus olor. Because Cu- and Zn-based pigments are employed in contemporary antifouling paints, concentrations of these metals were greatest in the preparations containing paint particles. Moreover, relative to total metal, both Cu and Zn displayed the highest gizzard bioaccessibilities in these preparations (about 10%). In the intestine, where most nutrients are absorbed, the accessibility of Cu was maintained while that of Zn was dramatically reduced. These observations were qualitatively consistent with metal concentrations measured in source materials relative to those in swan faeces. We conclude that Cu poses the greatest threat to C. olor inhabiting coastal areas where boat repair takes place.     

Degradation of pesticides in biobeds: the effect of concentration and pesticide mixtures

Biobeds aim to create an environment whereby any pesticide spills are retained and then degraded, thus reducing the potential for surface or groundwater contamination. Biobeds may receive high concentrations of relatively complex mixtures of pesticides. The effects of concentration and pesticide interaction on degradation rate were therefore investigated. At concentrations up to 20 times the maximum recommended application rate for isoproturon and chlorothalonil, the rate of degradation in topsoil and biomix decreased with increasing concentration. With the exception of isoproturon at concentrations above 11 mg kg(-1), degradation was quicker in biomix (a composted mixture of topsoil, compost, and wheat straw) than in topsoil. One possible explanation for faster isoproturon degradation in topsoil as compared to biomix may be that previous treatments of isoproturon applied to the field soil as part of normal agricultural practices had resulted in proliferation of microbial communities specifically adapted to use isoproturon as an energy source. Such microbial adaptation could enhance the performance of a biobed. Studies with a mixture of isoproturon and chlorothalonil showed that interactions between pesticides are possible. In biomix, the degradation of either isoproturon or chlorothalonil was unaffected by the presence of the other pesticide, whereas in topsoil, isoproturon DT(50) values increased from 18.5 to 71.5 days in the presence of chlorothalonil. These studies suggest that biobeds appear capable of treating high concentrations of more than one pesticide.     

Effects of nutrient supply and below-ground herbivory by Diaprepes abbreviatus L. (Coleoptera: Curculionidae) on citrus growth and mineral content

Three-year-old citrus trees were grown in the greenhouse to study the effects of fertilizer concentration and root herbivory on plant growth and mineral concentration. In separate experiments, sour orange (Citrus aurantium L.) and Swingle citrumelo (C. paradisi Macf. × Poncirus trifoliate L.) plants were treated with a complete fertilizer diluted to provide 25, 100, 200, or 400 ppm N and grown for 7 weeks with or without Diaprepes abbreviatus L. larvae. Increased fertilizer concentration increased the shoot mass and the shoot:root ratio of both sour orange and Swingle citrumelo. Root herbivory also increased the shoot:root ratio by depressing root growth more than shoot growth. Effects of root herbivory on growth were consistent across the four levels of fertilizer concentration, indicating that tolerance is not a function of nutrient status. For both rootstocks, concentrations of nitrogen in roots and leaves increased with fertilizer concentration, and C:N ratios decreased. In sour orange, root herbivory most strongly affected the concentration of carbon in roots, whereas in Swingle citrumelo, root herbivory most strongly affected leaf nitrogen. In general, herbivory reduced mineral concentrations of roots but the strength, and sometimes the direction, of herbivore effects varied significantly among fertilizer treatments. This research indicates that application of excess, balanced fertilizer is unlikely to offset growth reductions due to root herbivory by D. abbreviatus, and suggests that supplementation of specific nutrients may be of value.     

Sugarmill effluent effects on growth,photosynthetic pigments and nutrient uptake in wheat seedlings in aqueous vs. soil medium

Germination, seedling growth, concentrations of photosynthetic pigments and nutrient uptake inTriticum vulgare L. (Var. W-H-147) were studied in response to sugarmill effluent application (10% concentration) in aqueous Vs. soil medium. The effluent rich in various nutrients showed particularly high concentration of sodium. Germination was not affected by the effluent treatment. Seedling growth was reduced significantly by the effluent in aqueous medium, but not in soil. The effluent treatment increased the concentrations of various pigments, however, the pigment ratios got changed in the aqueous medium only. The uptake of nitrogen, magnesium and carbon by the seedlings decreased while that of calcium, sodium and phosphorus increased in effluent treated plants, the changes being more marked in aqueous medium except for phosphorus. In the effluent treated plants, uptake of potassium and chloride increased in aqueous medium, hut decreased sharply in soil.     

Pesticide inactivation of peanut glutamate dehydrogenase: biochemical basis of the enzyme's isomerization.

Glutamate dehydrogenase (GDH) isomerizes in response to pesticides and environmental chemicals, but the biochemical basis of the isomerization is not known. Clearer understanding of the isomerization would permit expansion of its utility in the diagnosis of the responses of plant tissues to challenged environments. Peanut plants were treated with different rates of Basagran (3-(1-methylethyl)-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide), Bravo 720 (tetrachloroiso-phthalonitrile), and Sevin XLR Plus (1-naphthyl N-methylcarbamate). Free solution isoelectric focusing, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) fractionated the peanut seed GDH to its constituent subunits and degradation polypeptides. After western transfer to nitrocellulose membrane, the GDH subunits and degradation polypeptides were immunodetected with anti-GDH. The pesticide treatments did not induce increased proteolytic activity, but induced about 50% degradation of the GDH, whereas the GDH of the control peanut suffered only about 25% degradation, thus showing that the degradation rate was about double the rate of de novo synthesis in the pesticide treatments. The heavy displacement of the GDH subunit equilibrium toward degradation explains the biochemical basis of the isomerization reaction.     

Toxic effects of two organophosphate insecticides,monocrotophos and dichlorvos to common earthworm Lampito Mauritii (Kinberg)

The lethal concentrations (LC₅₀ 96 h^?1) were measured experimentally by exposing the earthworms (Lampito mauritii) in moist vermiculite and in water. The morphological changes observed during the exposure of animals to the monocrotophos and dichlorvos were outlined. The mortality rate was higher in the water medium than in moist vermiculite. The hyperactivity at low pesticide concentrations is found to influence the size of the population.     

Enhanced Accumulation of Arsenate in Carp in the Presence of Titanium Dioxide Nanoparticles

In this study adsorption of arsenic (As) onto TiO₂ nanoparticles and the facilitated transport of As into carp (Cyprinus carpio) by TiO₂ nanoparticles was examined. Adsorption kinetics and adsorption isotherm were conducted by adding As(V) to TiO₂ suspensions. Facilitated transport of As by TiO₂ nanoparticles was assessed by accumulation tests exposing carp to As(V) contaminated water in the presence of TiO₂ nanoparticles. The results showed that TiO₂ nanoparticles had a significant adsorption capacity for As(V). Equilibrium was established within 30 min and the isotherm data was described by Freundlich isotherm. The K_F and 1/n were 20.71 mg/g and 0.58, respectively. When exposed to As(V)-contaminated water in the presence of TiO₂ nanoparticles, carp accumulated considerably more As, and As concentration in carp increased by 132% after 25 days exposure. Considerable As and TiO₂ accumulated in intestine, stomach and gills of the fish, and the lowest level of accumulation was found in muscle. Accumulation of As and TiO₂ in stomach, intestine and gills are significant. Arsenic accumulation in these tissues was enhanced by the presence of TiO₂ nanoparticles. TiO₂ nanoparticles that have accumulated in intestine and gills may release adsorbed As and As bound on TiO₂ nanoparticles which cannot be released maybe transported by TiO₂ nanoparticles as they transferred in the body. In this work, an enhancement of 80% and 126% As concentration in liver and muscle after 20 days of exposure was found.     

A field lysimeter study to evaluate herbicide transport in a wyoming irrigated pasture

Abstract

A field study was conducted to assess the fate and mobility of two commonly used herbicides, dicamba (3,6‐dichloro‐2‐methoxybenzoic acid), and picloram (4‐amino‐3,5,6, trichloro‐2 pyridinecarboxylic acid), in an irrigated pasture. The herbicides were applied at two application rates to four plots (two replicates) that contained soil‐water collectors. Herbicide concentrations as a function of depth and application rate were evaluated statistically to determine if replicate data could be combined. Results indicated dicamba concentration variations were low, suggesting the mean value of the replicate plots could be compared; however, picloram concentration variations were high, and the replicate plot data could not be combined. Half‐time values for herbicide disappearance (time required for herbicide concentration to diminish from its maximum to half maximum levels), calculated from the arithmetic mean of the logistic equations, were found to be useful in describing herbicide transport. Half‐time values were dependent upon application rate, collector depth, pesticide type, and plot location. Dicamba applied at the low application rate was detected at 15 and 30 cm depths only, and was not detected throughout the entire study period (467 days) at deeper depths. Significant differences occurred between plots receiving the high dicamba application rate, which was attributed to permeability differences that affected herbicide migration in the soil profile. Picloram half‐time values were also affected by soil organic carbon, which increased picloram adsorption. In general, differences in herbicide concentrations were observed within plots receiving the high picloram application rates, which was primarily attributed to spatial differences in hydraulic conductivity. Herbicide disappearance was most rapid at the shallow depth (e.g., 15 cm) within plots receiving lower herbicide application rates.     

铜对土壤中功夫菊酯和氯氰菊酯迁移和扩散的影响

Repeated applications of bordeaux mixture （a blend of copper sulfate and calcium hydroxide） and pyrethroid insecticides （Pys） have led to elevated copper （Cu） and Pys concentrations in vineyard surface soils. To understand the potential influence of Cu on the fate of Pys in the soil environment, we selected two Pys, cypermethrin （CPM） and lambda-cyhalothrin （λ-CHT）, and two typical Chinese vineyard soils, Haplic Acrisol and Luvic Phaeozem, as experimental samples. The dissipation experiment was conducted at room temperature in the dark, and the transport of both Pys through the soils was investigated using soil thin-layer chromatography. The results showed that the transport of Pys in both soils increased as the Cu²⁺ concentration increased from 0 to 100 mg L^-1 , and Pys were more transportable in Haplic Acrisol （HA） than in Luvic Phaeozem （LP） under the same experimental conditions. For CPM, only 100 mg L^-1 of Cu²⁺ significantly （P<0.05） increased Pys transport through both soils relative to water. Lambda-CHT was significantly （P<0.05） transported through HA by all the Cu²⁺ concentrations compared to water, and all but the 1 mg L^-1 of Cu²⁺ significantly （P<0.05） increased the transport of λ-CHT through LP relative to water. However, the dissipation rates of CPM and λ-CHT decreased with the addition of Cu to soils. Our findings suggest that the risk of groundwater contamination by Pys increases in the soils with elevated Cu concentrations.     

Effects of aluminium ions on uptake of calcium,magnesium and nitrogen in Betula pendula seedlings growing at high and low nutrient supply rates

The effects of aluminium on plant nutrition in small birch plants (Betula pendula Roth) were investigated. By using relative addition rate (r _A, g g^?1 d^?1) of nutrients as the growth-controlling variable, it was possible to grow the plants at very low external nutrient concentrations and to simulate plant requirements at two different fertility levels. Before aluminium addition the plants were at steady-state relative growth rate, (R _G, g g^?1 d^?1). The two addition rates were free access of nutrients with R _G ≈ 0.215 d^?1, or nutrient-limited, R _Aand R _G=0.10 d^?1. Internal concentrations of calcium and magnesium decreased with increasing Al³⁺ conncentration in the nutrient solution while nitrogen concentrations in the plants remained unchanged or increased. It was demonstrated in both nutrition treatments that calcium and magnesium decrease per se does not reduce plant growth and that uptake has to be considered in relation to plant requirement at different growth rates. The interpretation of the effects of aluminium on Ca and Mg uptake and plant biomass development suggested that processes other than disturbances in Ca and Mg uptake are the cause of the decrease in growth.