Effect of aluminum on the growth of sugar maple in solution culture

Abstract

The effect of aluminum (Al) on the growth of sugar maple (Acersaccharum Marsh.) was studied in two experiments in nutrient solution containing from 0 to 2000 μM Al at pH 4. Visible symptoms of injury to shoots or roots were not observed in either experiment. Reductions in seedling shoot size at the 1000, 1500, and 2000 μM concentrations were readily apparent; however, root biomass for these same concentrations did not differ significantly from the pH 4 controls. A plot of the relative total dry matter accumulation versus Al in solution showed that above 600 μM Al total seedling biomass declined exponentially. Of the mineral elements examined in these experiments, Ca was the most severely affected by increasing Al in solution. Even at 100 μM Al reductions in leaf, stem, and root Ca content were 17, 13, and 50% of the pH 4 controls, respectively. Some stimulation of growth and slightly higher P and K tissue concentrations were observed at low (100–500 μM) Al concentrations. At higher Al levels, P, K, and Mg were also reduced below the tissue content of the controls. The Al critical toxicity level for a 20% reduction in total seedling biomass was found to be 137 μg Al g dry weight−1 for newly expanded leaves.