Plant-Soil Interactions at Low pH pp 35-42 | Cite as
Predicting toxicity of reactive ‘solution’ aluminium using kinetic speciation
Abstract
We assayed the toxicity of Al by measuring lengths of Medicago sativa roots that formed during 3 to 5 days of equilibration of seeds with swirled solutions. Toxicity of ‘solution’ Al, as evidenced by retarded root growth, was reliably predicted by the rapidly reactive (RR) labile Al, determined using the pyrocatechol violet kinetic speciation method of Bartlett et al. (1987). Compared to the slowly reactive (SR) or the total reactive (TR) values, the RR Al results had fewer irregularities caused by colloidal Al or soluble Al strongly complexed by excess hydroxyl, organic, or phosphate ligands and were much more responsive to differences in Al reactivity that influenced root growth. The Al was not toxic when RR Al tested below 5 μM. The RR test correctly predicted colloidal (Tyndall beam positive) Al phosphate as toxic in some treatments, and in others, non-toxic. Hydroxy Al polymers, formed by the slow titration of AlCl3 with NaOH (presumably including Al13), were clearly toxic, but toxicity was less when pH was increased by added hydroxyls. When the total Al concentration was kept constant, the degree of toxicity was inversely proportional to the pH and directly proportional to the RR Al test values. The pH was not a good predictor of toxicity of hydroxy Al when the Al concentration was varied, and not a good predictor of toxicity of phosphate or citrate Al at either constant or varied Al concentration. Desorption results suggest probable toxicity of any Al species that is adsorbed onto a root under the conditions of this study. The RR Al values appeared to integrate the variables affecting reactivity of Al and produce a clean separation between toxic and not toxic.
Key words
aluminium binding aluminium speciation aluminium toxicity root growth solution aluminiumPreview
Unable to display preview. Download preview PDF.
References
- Anderson H A, Berrow M L, Farmer V C, Hepburn A, Russell J D and Walker A D 1982 A reassessment of podzol formation precesses. J. Soil Sci. 33, 125–136.CrossRefGoogle Scholar
- Bartlett R J and Riego D C 1972a Effect of chelation on the toxicity of aluminum. Plant and Soil 37, 419–423.CrossRefGoogle Scholar
- Bartlett R J and Riego D C 1972b Toxicity of hydroxy aluminum in relation to pH and phosphorus. Soil Sci. 114, 194–200.CrossRefGoogle Scholar
- Bartlett R J, Ross D S and Magdoff F R 1987 Simple kinetic fractionation of reactive aluminum in soil’ solutions’. Soil Sci. Soc. Am. J. 51, 1480–1482.CrossRefGoogle Scholar
- Bertsch P M 1987 Conditions for Al13 polymer in partially neutralized aluminum solutions. Soil Sci. Soc. Am. J. 51, 825–831.CrossRefGoogle Scholar
- Bertsch P M and Anderson M A 1989 Speciation of aluminum in aqueous solutions using ion chromatography. Anal. Chem. 61, 535–539.PubMedCrossRefGoogle Scholar
- Childs C W, Parfitt R L and Lee R 1983 Movement of aluminum as an inorganic complex in some podzolized soils, New Zealand. Geoderma 29, 139–155.CrossRefGoogle Scholar
- Horst W J, Wagner A and Marschner H 1982 Mucilage protects root meristems from aluminum injury. Z. Pflan-zenphysiol. Bd. 105 S., 435–444.Google Scholar
- Hsu P H and Bates T F 1964 Formation of x-ray amorphous and crystalline aluminum hydroxides. Mineral. Mag. 33, 749–768.CrossRefGoogle Scholar
- Jardine P M and Zelazny L W 1987 Influence of organic anions on the speciation of mononuclear and polynuclear aluminum by ferron. Soil Sci. Soc. Am. J. 51, 885–892.CrossRefGoogle Scholar
- Kinraide T B 1991 Identity of rhizotoxic aluminum species. Plant and Soil 134, 167–178.Google Scholar
- Parker D R, Kinraide T B and Zelazny L W 1988a Aluminum speciation and phytotoxicity in dilute hydroxy-aluminum solutions. Soil Sci. Soc. Am. J. 52, 438–444.CrossRefGoogle Scholar
- Parker D R, Kinraide T B and Zelazny L W 1989 On the phytotoxicity of polynuclear hydroxy-aluminum complexes. Soil Sci. Soc. Am. J. 53, 789–796.CrossRefGoogle Scholar
- Parker D R, Zelazny L W and Kinraide T B 1988b Comparison of three spectrophotometric methods for differentiating mono-and polynuclear hydroxy-aluminum complexes. Soil Sci. Soc. Am. J. 52, 67–75.CrossRefGoogle Scholar
- Taylor R M 1988 Proposed mechanism for the formation of soluble Si-Al and Fe-Al hydroxy complexes in soils. Geoderma 42, 65–77.CrossRefGoogle Scholar
- Wagatsuma T and Kaneko M 1987 High toxicity of hydroxy-aluminum polymer ions to plant roots. Soil Sci. Plant Nutr. 33, 57–67.CrossRefGoogle Scholar