Plant and Soil

, Volume 332, Issue 1–2, pp 319–330 | Cite as

Comparative hydrolysis and sorption of Al and La onto plant cell wall material and pectic materials

  • J. Bernhard Wehr
  • F. Pax C. Blamey
  • Peter M. Kopittke
  • Neal W. Menzies
Regular Article


Pectin, which is an important component of plant cell walls, strongly binds Al and this may play a role in expression of Al toxicity. Sorption of aluminium (Al) and lanthanum (La) from aqueous solutions onto pectic acid, Ca-pectate and plant cell wall material was pH dependent. For Al at pH 3, sorption was less than the available sorption sites (i.e., the cation exchange capacity) on all three sorbents, whereas at pH 4, sorption of Al was in excess of available sorption capacity. By contrast, sorption of the trivalent Al analogue La corresponded to the available sorption capacity on all three sorbents at pH 5. This indicates, therefore, that Al hydrolyses at ≥ pH 4, and hydrolysis increases with Al concentration in solution. Further, it is proposed that the sorption of Al to pectin leads to deprotonation of the galacturonic acid (GalA) residues. Sorption of Al to pectin limits hydrolysis of Al, thereby shifting the pH of hydrolysis to a higher value. Hydrolysis of Al results in its sorption in excess of the stoichiometric equivalent (assuming the free Al3+ ion), leading to oversaturation of the pectin with Al. Staining of the metal-pectate complexes with the metachromatic dye eosin showed that with increasing Al saturation (but not La saturation), the complex developed a positive net charge, due to formation of some positively charged Al-complexes. The development of a positive charge on the Al-pectate complex may have major effects on cellular transmembrane potential and nutrient acquisition by plant roots. This is the first report of Al binding in excess of binding sites and development of a net positive charge on Al-pectate.


Pectin Lanthanum Aluminum Adsorption Hydrolysis Metachromatic dyes Pectate 



Cation exchange capacity


Galacturonic acid


Inductively coupled plasma atomic emission spectroscopy


Sorption capacity


Langmuir sorption constant



This research was supported under the Australian Research Council’s Discovery Projects funding scheme (project number DP 0665467), a UQ Ernest Singer Scholarship, and an Australian Government Overseas Research Postgraduate Scholarship.


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Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  • J. Bernhard Wehr
    • 1
  • F. Pax C. Blamey
    • 1
  • Peter M. Kopittke
    • 1
    • 2
  • Neal W. Menzies
    • 1
    • 2
  1. 1.The University of Queensland, School of Land, Crop and Food SciencesSt LuciaAustralia
  2. 2.Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC-CARE)The University of QueenslandSt LuciaAustralia

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