Root morphology and nutritional status of Japanese red cedar saplings subjected to in situ levels of aluminum in forest soil solution

There is little information on the effects of in situ levels of aluminum (Al) in the forest soil solution on the root morphology of Japanese red cedar (Cryptomeria japonica D. Don). We evaluated whether morphological and nutritional changes in the white roots of Japanese red cedar saplings grown in glass-bead culture for 18 weeks occurred in response to Al solutions at five concentrations: 0 (control), 0.05, 0.1, 0.5, and 1.0mM. Branching white roots treated with 0.5 or 1.0mM Al had some stunted, brown, thickened tips. Their mean lengths were significantly shorter than those of roots treated with 0.05 or 0.1mM Al. The maximum diameters of white roots treated with 0.5 or 1.0mM Al were significantly larger than those of the control. Treatment with 0.5 or 1.0mM Al reduced the concentrations of Ca and Mg in the white roots and increased the concentration of Al compared with the control. These results indicate that between 0.1 and 0.5mM Al, a drastic change occurs in the effects of Al on the morphology and nutritional status of white roots of Japanese red cedar saplings, and suggest that the Al levels in Japanese forest soils may induce morphological changes in the white roots.