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pp.141-147
Effects of aluminium(Al), soil pH and calcium(Ca) on growth response and heavy metal accumulation and regulation of nitrogen fixation in Melilotus suaveolens seedlings, a biennial legume plant dominating in the disturbed area, were quantitatively analyzed during the growing periods. Accumulation of metals in each organ of M. suaveolens was increased with the lowering of pH. Al contents in leaf and root treated with 30ppm Al at pH 4.2 on the 28th day after treatment were 8 and 11 folds higher than those of control, while the contents with 100ppm Al were 21 and 24 folds as compared to control. The significent inhibition in Al contents was induced by 100ppm Al and Ca at pH 6.5. Increased metals inhibited height at pH 4.2 and the growth inhibition due to Al was reversed by the addition of Ca, suggesting that growth correlates to the pH value. Chlorophyll contents in leaves increased during growth stage were inhibited by Al treatments. The biomass was decreased with the lowering of pH and the increase of concentrations. 100ppm Ca treatment resulted in 5.1-5.9% increase of the biomass as compared to that of 100ppm Al. Specific nitrogen fixation activities in nodules in the 100ppm Al at pH 4.2 and pH 6.5 were reduced to 35. 2% and 52.2% of control, on the 28th day after treatment, while the combination of Al and Ca induced inhibition of activities to 4.6% and 69.9% of control, respectively. Total amount of nitrogen fixation was reduced by 10% as compared to control with the treatment of 100ppm Al at pH 4.2 due to the inhibition of nodule formation. However the stimulative effect of nodule formation was enhanced by the combination of 100ppm Al and Ca and lowering of pH.
