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This article in SSSAJ

  1. Vol. 52 No. 4, p. 1059-1063
     
    Received: Aug 20, 1987


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doi:10.2136/sssaj1988.03615995005200040030x

Comparison of Aluminon and 8-Hydroxyquinoline Methods in the Presence of Fluoride for Assaying Phytotoxic Aluminum

  1. A. D. Noble,
  2. M. E. Sumner and
  3. A. K. Alva 
  1. Dep. of Crop Science, Univ. of Natal, Pietermaritzburg, South Africa
    Dep. of Agronomy, Univ. of Georgia, Athens, GA 30602

Abstract

Abstract

A nutrient solution study was conducted to evaluate the effects of varying pH (4.2, 4.5, and 4.8), Al (0, 20, 40, and 80 µM Al) and F- (0, 10, 20, and 40 µM F-) on soybean [Glycine max (L.) Merr. cv. Lee] root growth. The ability of Al fractions measured by the modified aluminon and 8-hydroxyquinoline methods in predicting the phytotoxic component of Al was also investigated. In the presence of Al up to 40 µM, increasing levels of F- resulted in an increase in root length. Aluminum speciation in solutions predicted by GEOCHEM program showed an increase in concentration of F- complexed Al species with an increase in concentration of F-. A very poor relationship was observed between tap root length and the sum of predicted concentrations of F- complexed Al species. Thus, F- complexed Al species would appear to be less phytotoxic than the other Al monomers. A highly significant correlation was found between tap root length and predicted concentration of Al3+ (R2 = 0.971). The relationship was further improved when sum of predicted concentrations of Al3+ and hydroxy-Al species was considered (R2 = 0.986). Tap root length was poorly correlated with the concentration of monomeric Al determined by the modified aluminon method, which included a larger portion of less phytotoxic F- complexed Al species. In contrast, a highly significant correlation (R2 = 0.984) was found between tap root length and the concentration of labile Al determined by the 8-hydroxyquinoline (15-s reaction) method. The labile Al may include only a very small fraction of F- complexed Al species. Therefore, in solutions containing varying concentrations of F-, Al measured by the 8-hydroxyquinoline (15-s reaction) method is a better predictor of Al phytotoxicity than that measured by the modified aluminon method.

Contribution from the Dep. of Agronomy, Univ. of Georgia. Research supported by Florida Inst. of Phosphate Res. and Georgia Agric. Exp. Stn.

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