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Effect of aluminium and pH on the mobility of phosphate through a soil-root interface model

Carlo E. Gessa, Tanja Mimmo, Salvatore Deiana and Claudio Marzadori
Plant and Soil
Vol. 272, No. 1/2 (May 2005), pp. 301-311
Published by: Springer
Stable URL: http://www.jstor.org/stable/42951706
Page Count: 11
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Effect of aluminium and pH on the mobility of phosphate through a soil-root interface model
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Abstract

The aim of this work was to investigate the effect of aluminium (Al), a toxic metal for plant growth, as well as pH on the mobility of phosphate across a calcium-polygalacturonate (Ca-PG) network used as a soil-root interface model. The Ca-PG fibrils, having acidic properties, are able to complex ions selectively: thus a Ca-PG model could be useful to study the ion uptake by plants. Ca-PG networks were exposed to Al solutions at different concentrations (25, 100 and 200 µM) at pH 3.50, 4.00 and 4.50. These Ca-PG and Ca-Al-PG networks were subsequently used to measure the phosphate flux at pH 3.50, 4.00 and 4.50. The results showed that the phosphate's mobility across the soil-root interface is strongly influenced by pH and aluminium: its mobility is much greater at a low pH. The presence of Al slowed down the phosphate even more leading to a complete flux impedance in the first 3-5 h at pH 4.00 and 4.50. This impedance is probably not only due to interactions between phosphate and Al but it is also due to structural changes: the interaction of Al (hydrolytic and/or polymeric species) at pH 4.00 and 4.50 with the polygalacturonic chains could lead to a collapse of the porous structure. These results suggest that the apoplastic-bound Al hinders, especially at pH 4.00 and 4.50, the phosphate uptake by plants.

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