The use of root growth and modelling data to investigate amelioration of aluminium toxicity by silicon in Picea abies seedlings.

M. Ryder¹, F. Gerard², D.E. Evans¹, and M.J. Hodson¹.

Three week old Picea abies seedlings were grown for 7 days in 100µM Al, combined with 1000 or 2000µM silicon (Si). Solution pH was adjusted to 4.00, 4.25, 4.50, 4.75, or 5.00. At pH 4.00 Si did not ameliorate toxic effects of Al on root growth, whereas increasing amelioration was found as the pH increased. Complete amelioration of Al toxicity was recorded at pH 5.00.

An equilibrium speciation model (EQ3NR), with a current thermodynamic database was used to predict the behaviour of Al and Si in growth solutions. Al³⁺ content was higher for runs where formation of hydroxyaluminosilicates (HAS) was not permitted, than where the possibility of HAS formation was included. Solutions were modelled to include HAS formation, the concentration of Al³⁺ decreased from about 80% of Al species at pH 4.00, to approx. 18% of Al at pH 5.00. There was an increase in HAS content, showing an inverse relationship with Al³⁺.

Michelle Ryder
Tel. 01865 483267
E-mail: mryder@brookes.ac.uk

1. School of Biological and Molecular Sciences. Oxford Brookes University, Headington Campus, Gipsy Lane, Oxford, OX3 0BP, UK.
2. INRA - Centre de Recherches Forestières. Unité Biogéochimie des Ecosystèmes Forestiers, Forêt d'Amance, 54280, Champenoux, France.