Effects of Cd²⁺ and Zn²⁺ on Seed Germination and Seedling Growth of Triticum aestivum and 2 Weed Species

In this study, distilled water was used as CK to determine the effects of Zn²⁺ and Cd²⁺ single stress on seed germination and seedling growth of Triticum aestivum, Echinochloa crusgalli and Kochia scoparia, and the tolerance of 3 kinds of plants to Zn²⁺ and Cd²⁺ was evaluated by membership function method. The results show that the response of the seeds germination and seedling growth of different seeds are not the same under the 2 metal ions stresses. With the increase of Cd²⁺ and Zn²⁺ concentration, the relative seed germination rates, germination indices and the vigor indices of 3 kinds of plants decreased except that the vigor indices is higher than CK under 50 mg/L Zn²⁺ concentration. With the increase of Cd²⁺ concentration, the relative root length and relative shoot length of T. aestivum and E. crusgalli seedlings decrease and the relative root length of K. scoparia seedlings is significantly higher than CK under 25 and 50 mg/L Cd²⁺ concentration. The relative root length of E. crusgalli seedlings treated with Zn²⁺ of 50, 100, 200 and 400 mg/L are significantly higher than CK. The relative shoot length of E. crusgalli seedlings treated with 50 and 100 mg/L Zn²⁺ are significantly higher than CK. The relative root length and relative shoot length of Triticum aestivumt and Kochia scoparia seedlings are significantly higher than CK under the treatment of 50 mg/L Zn²⁺. The resistance of seed to Cd²⁺ stress is ordered as K. scoparia > T. aestivum > E. crusgalli, and to Zn²⁺ stress is ordered as E. crusgalli > K. scoparia > T. aestivum. Comprehensive analysis shows that Kochia scoparia and Echinochloa crusgalli seeds have strong resistance to Cd²⁺ and Zn²⁺ respectively during seed germination period.