| Aluminum(Al) toxicity is a major constraint to crop productivity in acid soils. The root growth is hurted by Al stress and absorbability of water and nutrient decreased, so the growth and development of plant is limited. In this study, we investigated the ability of Al-tolerance of twenty-four soybean cultivars by breeding in hydroponics and screened Al-tolerant genotype, Jilin 62 and Al-sensitive genotype, Jiyu 54. The root growth as well as physiological mechanisms of Al resistance and some alleviating effect by supplying Mg and B was studied on Jilin 62 and Jiyu 54. The results showed that different soybean genotypes differed in tolerance in Al stress by root elongation measuring. The cultivar Jilin 62 and Jiyu 54 were Al-tolerant and Al-sensitive genotypes respectively. The stress of Al on soybean is inhibition of root elongation and Jilin 62 was less inhibited in root growth than Jiyu 54 over the whole range of Al concentrations. The relative root elongation rate of Jilin 62 is 96.8%-32.2% and Jiyu 54 is 59.6%-10.5% in 10-40μM Al concentration. Result of mensuration of Al content in root apices showed that the Al-sensitive genotype cumulated more Al than Al-tolerant genotype. The Al content in root apices of Jiyu 54 is 1.62-8.33 nmol﹒apex-1 and Jilin 62 is 0.47-7.01 nmol﹒apex-1 in 10-40μM Al concentration. The Al-induced organic acid is one of the most important Al-tolerant mechanisms in plant. The citrate was secreted specially from the root of...
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