Aluminum Effects on Picea abies at Low Solution Concentrations

The usual way to evaluate Al toxicity in forest ecosystems is to consider the concentration of Al3+ in soil solution. The objective of this paper is to show that Al may affect tree seedlings even under conditions of very low bulk-soil solution concentrations of Al. Picea abies (L.) H. Karst. seedlings, with or without ectomycorrhizal inoculation [Hebeloma crustuliniforme (Bull.: St. Amans) Quél.], were grown in perlite substrate with addition of 0, 0.1, and 0.5 mM Al. The perlite buffered the pH at values > 5 and no soluble Al was detected in the system. However, plant biomass was significantly reduced when 0.5 mM Al was added without fungal inoculation, and Al uptake was 2 to 3 times higher than in the control treatment. Fungal inoculation compensated the growth reduction, but did not reduce Al uptake. These results indicate that spruce seedlings are able to mobilize and take up Al from solid phases.