A resin buffered method for controlling metal speciation in nutrient solutions for plant toxicity tests

Author: Versieren Liske   Smets Elke   Smolders Erik  

Publisher: Springer Publishing Company

ISSN: 0032-079X

Source: Plant and Soil, Vol.373, Iss.1-2, 2013-12, pp. : 257-267

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Abstract

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.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.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.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.