ALTERED ROOT-GROWTH AND PLANT CHEMISTRY OF PINUS-SYLVESTRIS SEEDLINGSSUBJECTED TO ALUMINUM IN NUTRIENT SOLUTION

One-year-old Scots pine (Pinus sylvestris L.) seedlings were grown for 9 weeks in nutrient solutions containing 0, 0.5, 1, 2 and 4 mM alumin um nitrate (Al(NO3)(3)) at pH 4.2. Nine weeks exposure to Al significa ntly reduced total plant, shoot and root mass and caused a linear decl ine in proportional allocation of biomass to roots. Relative growth ra te of roots declined to as low as zero. Aluminum treatment decreased c alcium and magnesium uptake and increased Al content in roots and need les. After 3 weeks of exposure a 10-60% increase in total phenols in r oots and a 20-40% increase in o-diphenols in roots and needles were no ted. Roots affected by Al showed degeneration of meristematic cells, f ewer cell divisions, deformation in cell walls and higher lignificatio n and suberization. The majority of root apices were structurally simi lar to dormant roots, and a premature senescence of the entire root sy stem was observed. Net photosynthetic rate after 6 weeks of treatment was negatively correlated with needle Al content and Al/Ca ratio (I < -0.9, P < 0.1). The results suggest that Scots pine may be more suscep tible to Al than was expected based on previous experiments.