The effect of aluminum on seed germination and early seedling establishment, growth, and respiration of white spruce (Picea glauca)

Abstract

Seed germination and the establishment and subsequent growth of seedlings of white spruce (Picea glauca (Moench) Voss) subjected to various aluminum treatments were examined. Aluminum concentrations of 50–500 μM did not reduce the cumulative percent germination of seeds but impaired the ability of seedlings to become established. The inability of roots of Al-treated seedlings to penetrate a rooting medium resulted in significant reductions in seedling fresh weight and in the length and dry weight of roots and shoots. When seedlings were established before exposure to Al, the deleterious effects of Al were not as pronounced; however, root length, root dry weight, and root to shoot ratio were significantly lower for Al-treated seedlings compared with controls. Aluminum stimulated shoot growth, and a trend towards increased shoot length and stem dry weight with increased Al concentration was observed. Increased Al concentration in solution decreased the root to shoot ratio of established seedlings, but significant differences in respiration rate among Al treatments were not evident. The minimal Al concentration at which root elongation and the root dry weight of white spruce seedlings was significantly reduced was 50 μM, a value generally lower than those reported for other North American tree species. This suggests that white spruce seedlings are sensitive to aluminum and that soil acidification with its related increase in soluble aluminum may inhibit the natural establishment of this species.