Die Reaktion von Fichtenwurzeln auf Aluminium-Behandlung in Hydrokultur

Abstract

The mechanisms which lead to aluminium tolerance of forest trees are largely unknown. Three years old mycorrhizal Norway spruce trees were treated for one week with 0,5 mm AlC1₃ or CaC1₂ solutions at pH 4. Different mechanisms were checked for their role in protecting the plants from toxic concentrations of Al³⁺. At the beginning of the treatments, a rapid cation exchange occurred at the root surface where A1³⁺ displaced adsorbed nutrient cations. A sequential extraction at the end of the treatments revealed, however, that part of the Al was bound in a non-exchangeable but acid soluble form. Al treatment did not increase total carbon released into solution. The only strongly complexing organic acid found in solution was oxalic acid which, however, was present only in micromolar amounts. Nitrate reductase activity did not differ between the treatments.

If Al was present at high concentrations in the solution, the formation of high molecular structures consisting of several Al atoms with inorganic and phenolic ligands could be observed. However, since the total release of phenolics was not enhanced by Al treatment, this process probably is not actively controlled by the plant but rather represents a passive protection.