Abstract
In this study the toxic effect of soluble inorganic aluminium on Scots pine and Norway spruce seedlings was tested at five aluminium (0, 5, 10, 20, 50 mg All −1) and two nutritional levels. Mineral nutrients and aluminium were both given via the irrigation water. The nutrients were supplied at the optimal ratio suggested by Ingestad (Ingestad, T., 1979. Mineral nutrient requirements of Pinus sylvestris and Picea abies seedlings. Physiol. Plant. 45: 373–380), and at ratio in which all the other nutrients apart from nitrogen were reduced to one-tenth of the optimal level. The experiment was carried out beneath a plastic roof under field conditions. The seedlings were grown in 4-1 containers filled with quartz sand. The experiment with 1-year-old pine seedlings lasted for two growing season. The spruce experiment consisted of four seed provenances which were sown on 25 May 1989, and harvested at the beginning of November 1989. When the nutrition of the pine seedlings was optimal, the Al treatments did not reduce growth during the experimental period. The Al treatments were not found to have had growth-reducing or toxic effects on the seedlings with suboptimal nutrition after the seedlings started to die after the shoots had ceased height growth. This was even the case with the lowest Al treatment, where the growth was also reduced markedly. Independent of nutrient level or seed provenance, all the Al treatments reduced the growth of Norway spruce seedlings, and at the 50 mg Al l −1 treatment level growth was nearly totally inhibited. It seems evident that when nutrition is optimal, pine seedlings can withstand high levels of aluminium without any adverse effect on growth. However, when nutrition is suboptimal, toxic effects of Al occur at concentrations that are also to be found in the field.
Published Version
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