Abstract：Abstract Cadmium (Cd) is a highly toxic and persistent environmental poison, its increasing level in environment exerts a wild range of adverse effects on wheat (Triticum aestivum) and even the health of human beings by food chains. In order to clarify the mechanism of Cd poisoning on wheat, we studied the effects of different concentrations (0, 10, 20, and 40 mg/L) of Cd solution (CdCl2·2.5H2O) on Zhongyu 10, Zhoumai 18 and Luomai 23 in seed development and physiological mechanism. We studied the effects of different Cd concentrations on some physiological indexes including peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), soluble sugar, soluble protein, malondialdehyde (MDA), proline content, root vigor, and photosynthetic indexes. Then the ultrastructure of root cells was observed. Research results showed that the germination rates of Zhongyu 10 (strong Cd tolerance), Zhoumai 18 (medium Cd tolerance) and Luomai 23 (low Cd tolerance) decreased by 12%, 20% and 42% under the treat with 20 mg/L Cd solution, respectively. The growth of wheat was inhibited as the Cd solution concentration increased. Under 40 mg/L Cd solution, the root length of Zhongyu 10 decreased by 69%, and the root length of Luomai 23 decreased by 80%. Besides, POD activity, SOD activity, CAT activity, soluble protein content, soluble sugar content, MDA content, proline content and intercellular CO2 concentration all increased in flag leaves at seeding stage. Zhongyu 10 increased more than Luomai 23, and exhibited some adaptability. While root activity, net photosynthetic rate, transpiration rate, and stomatal conductance all decreased, and Luomai 23 decreased more than Zhongyu 10. In addition, root cells were observed by transmission electron microscopy, and showed that the damages of mitochondria, cell wall and cell membrane of root cells in Luomai 23 were more serious than that of Zhongyu 10. The present study explored the responses of 3 strains of wheat with different Cd tolerance including growth morphology, physiological metabolism and ultrastructure, which might provide certain reference for wheat genetic breeding.
