A resin buffered method for controlling metal speciation in nutrient solutions for plant toxicity tests |
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Authors: | Liske Versieren Elke Smets Erik Smolders |
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Institution: | 1. Division Soil and Water Management, Department of Earth and Environmental Science, KU Leuven, Leuven, Belgium 2. Kasteelpark Arenberg 20, 3001, Heverlee, Belgium
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Abstract: | Aims Root elongation tests are sensitive bioassays for testing metal toxicity in nutrient solutions. The metal speciation and, hence, metal exposure conditions are little controlled in the traditional set-up. A resin buffered solution system was developed to overcome this issue. Methods Barley (Hordeum vulgare L.) root elongation was tested in aerated 140 mL solution batch systems supplied with 3.3 g Dowex resin for two plants. Copper toxicity was measured in presence or absence of the resin (+R/?R) and in presence or absence of a metal complexing ligand (+NTA; nitrilotriacetic acid/?NTA). In addition, the toxicity in the traditional set without resin and with daily solution replacement was included as a reference. Results Metal desorption from the resin is fast in these systems (k?=?0.82 h?1). Total dissolved Cu roughly halved during 4 days in ?R/?NTA systems due to uptake, while it increased by 30 % in the +R/?NTA, probably due to complexation reactions by root-derived molecules. The toxicity (50 % reduction in root length, EC50) of the initial free Cu2+ was equal in all resin or chelate buffered systems and in the solutions with daily replacement, whereas this threshold was significantly larger in the ?R/?NTA due to Cu2+ uptake and complexation reactions. Conclusion The resin method is a convenient system for high throughput screening of metal toxicity and avoids uncertainties in metal speciation inherent to chelator buffered systems. Details are given how to prepare the resin to obtain a target metal ion activity. |
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