| Vegetable soybean is welcomed by most people for its rich nutrients and special flavour, there is a growing demands for vegetable soybean in both home and abroad market. As a main vegetable soybean exporting country of the world, China has a rapid rising in cultivation of vegetable soybean these years. With the increasing industrialization and urbanization, heavy metal pollution in farmland soil is becoming more and more serious due to abundance of pollution sources, such as three kinds of the industrial waste, domestic pollutant, and unreasonable use of pesticide and chemical fertilizer. Vegetable soybean is mainly planted in suburb areas, plenty of vegetables provide to cities are from these areas, but suburb areas faced the problem of being polluted by heavy metal and out of the heavy metal content limits.Three vegetable soybeans, Texuan-75, Kaixin-1 and Gaoxiong-3 were selected as experimental material in this research, to address the accumulation capability and heterogeneous tolerance capability of vegetable soybeans under the stress of different Cd2+ concentration in order toprovide some information for food hygiene of vegetable soybean from polluted farmland. The results are as following:(1)Cd2+ has a toxic effect on vegetable soybean. When Cd2+ concentration is under 0.5 mg.kg-1, it promotes the growth of plant. While Cd2+ concentration is between 0.5 mg.kg-1 and 1 mg.kg-1, it has a suppression effect though unconspicuous on the growth of plant. If Cd2+ concentration is above 2 mg.kg-1, the suppression effect becomes obvious.(2)Vegetable soybean varieties have differences in Cd2+tolerance capability under Cd stress. Statistics shows that low stress tolerance capability varieties are more sensitive to Cd2+stress than high stress tolerance capability varieties. In thisr study, Gaoxiong-3 is the most sensitive variety to Cd2+stress and is harmed at 0.5 mg.kg-1 Cd2+ concentration.(3)Under Cd2+ stress, vegetable soybean varieties are various in physiological and biochemical characteristics. Within the tolerance capability range, resistance indexes rise with the Cd2+ concentration, while up to or exceeding the critical concentration, resistance indexes descends sharply. Among the selected soybean varieties, Texuan-75 shows the highest tolerance capability while Gaoxiong-3 shows the lowest tolerance capability.(4) Vegetable soybean varieties have significant difference in Cd2+ accumulation capability and also various in different parts Cd2+ accumulation capability. There are significant Cd2+ accumulation difference among the selected soybean varieties, Gaoxiong-3 shows the highest capability while Texuan-7 shows the lowest capability. The order of different parts'Cd2+ accumulation capability is:root> stem> leaf. Under low Cd2+ stress concentration, the differences among parts are small, but increase significantly with the stress concentration increasing. (5)Though edible parts of vegetable soybean have relative low Cd2+ accumulation capability, the Cd2+ accumulation content is higher than the national standard. Therefore, it is inappropriate to cultivate vegetable soybean in Cd2+ polluted farmland. |
