ALUMINUM TOXICITY AS A FACTOR LIMITING THE DISTRIBUTION OF ALLIUM-URSINUM (L)

Solution experiments and analyses of soil solutions from the field were made to elucidate whether the A1 concentration in the soil water of dystric cam bisols could be a factor restricting Allium ursinum to less acid soils. Two size classes of A. ursinum were exposed, for 4 weeks to a synthetic soil solution of pH 4'3 containing 0, 20, 40 and 70 //, m Al, using a flowing solution culture system. An Al concentration of 20 fiu, at a Ca/Al molar ratio of 12-5, was toxic to the plants, as shown by a cessation of root extension and slower root dry weight production. Compared to mature plants, seedlings developed Al toxicity symptoms after shorter exposures to Al and negative effects on the shoots were displayed at smaller Al concentrations in solution. The high sensitivity of this species to Al, and the maximum soil solution concentration of available Al present at the most acid sites that support A. ursinum, indicate that Al and the Ca/Al ratio may determine the field distribution. © 1993 Annals of Botany Company.