Abstract: Recently in animals, endogenous carbon monoxide (CO), like nitric oxide, was implicated as another important physiological messenger or bioactive molecule. However, little information is known about the physiological roles of CO in the whole plant. In the present study, we report that different concentrations of the CO donor hematin (0.1, 1.0 and 10.0 mol/L) alleviated wheat (Triticum aestivum L. Yangmai 158) seed germination inhibition caused by 250 mmol/L NaCl stress in a dose-dependent manner. These responses were also proved by the addition of different gaseous CO aqueous solutions from 0.1% to 100.0% of saturation. Among these treatments, the effect of 1.0 mol/L hematin and 1.0% saturation of CO aqueous solution were the most obvious. Furthermore, compared with non-hematin treatment, the degradation of storage reserves in wheat seeds was also accelerated. Time-course analyses showed that application of hematin dose-dependently increased the activities of superoxide dismutase, catalase, ascorbate peroxidase, and guaiacol peroxidase activities, thus decreasing the lipid peroxidation in germinating wheat seed subjected to salt stress. Meanwhile, the responses of hematin were specific for CO because the addition of the CO scavenger hemoglobin (0.2 g/L) blocked the various actions of 1.0 mol/L hematin. Taken together, the results of the present study demonstrate that CO, at a low concentration, is able to attenuate the seed germination inhibition produced by salinity stress and counteract the lipid peroxidation in germinating wheat seeds.（Author for correspondence. Tel (Fax): +86 (0)25 8439 6673; E-mail: wbshenh@njau.edu.cn）

Key words: carbon monoxide, lipid peroxidation, salt stress, seed germination, storage reserve degradation, wheat.