| At present, the content of nickel has increased in the black soil year by year, appearing different degrees of nickel contamination. Therefore, studying nickel stress on crop growth has important significance. This paper investigated the effect of different concentration nickel stress on the physiological indexes of plant seedling and this pot experiment approach to maize and soybeans as materials. The results indicated as follows:The study found that maize seedlings have strong resistance to heavy metal nickel. When the applied nickel concentration 100 mg/kg, the content of effective nickel in soil with DTPA extracting is 34.05mg/kg, which can cause maize mild poisoning. The results of our research show that the low concentration of nickel can promote the growth and increase SOD and CAT activity of the maize seedlings leaves. However, with the increase of the concentration nickel, SOD and CAT activity is inhibited and the levels of POD activity maintained relatively high. With the increase concentration of applied nickel, the Pro content increases at first and then decreases. And conductivity has been increased. When corn seedlings cultured between 10 and 20 days, low concentrations of nickel (≤50mg/kg) can increase ascorbic acid Oxidase and PPO activity, but inhibitory effect under high concentration.The results indicated that nickel had promote effect under low nickel Concentrations but inhibitory effect under high concentration for maize seedlings root, and the inhibitory effect gradually increased with the increasing concentration. The long of root, the weight of fresh root, root activity, SOD and POD activities, the content of MDA have the same trend in the three processing stages(10,20,30d), with the growth of the maize seedlings, physiological index changes significantly. The root activity is highest at the Ni2+ concentration of 50mg/kg in the soil, and decreases markedly with the Ni2+ concentration increased; With the increase of nickel concentration, while SOD and POD activities in protective systems rose at first and then decreased; when maize seedling were treated with 50mg/kg Ni2+, SOD and POD activities reached the maximum; MDA content in root cells increases slightly in the low concentration of nickel, however increases significantly in the nickel concentration between 100 and 800 mg/kg.The study found that soybean seedlings are sensitive to heavy metal nickel. When the applied nickel concentration less than 50mg/kg, the plants grow up best. When the applied nickel concentration is 30mg/kg(soil), the soil available nickel concentration is 7.74mg/kg,the changes of plant physiological index are most significant and antioxidant enzyme activity is relatively high. The plant of soybean grow slowly, growth become small, the content of MDA and conductivity increases, cell membrance structure was destructed with the content of effective nickel in soil more than 15.89 mg/kg. When soybean seedlings are cultured 10 days, terminal oxidase activity can increase under low concentrations of nickel, but inhibitory effect under high concentration..The soybean root is more sensitive to the concentration of nickel stress, the root activity is high, grow up best with the applied nickel concentration 30mg/kg.but the root activity significantly reduced, Enzymes is inhabited in plant, the content of MDA is increased with the applied nickel concentration 50mg/kg.The root is short, almost lose its activity at nickel concentration 150 mg/kg.The study found that maize seedlings has strong resistance, the root system is weaker than leaves on the impact of heavy metal nickel stress. However, the soybean seedling resistance is weak, the nickel concentration has relatively great impact on soybean seedling and the impact on root is more serious than leaves. The results indicated that the plant physiological index affected by the nickel stress most significantly when maize and soybean seedlings are cultured 10 days.
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