Abstract: Carbon monoxide (CO), a by-product released during the degradation of heme by heme oxygenases (EC 1.14.99.3) in animals, is regarded as an important physiological messenger or bioactive molecule involved in many biological events that has been recently reported as playing a major role in mediating the cytoprotection against oxidant-induced lung injury. In the present study, we first determined the protective effect of exogenous CO against salt-induced oxidative damage in wheat seedling leaves. Wheat seedlings treated with 0.01 mol/L hematin as the CO donor demonstrated significant reversal of chlorophyll decay, dry weight, and water loss induced by 300 mmol/L NaCl stress. Interestingly, the increase in lipid peroxidation observed in salt-treated leaves was reversed by 0.01μmol/L hematin treatment. Time-course analyses showed that application of 0.01μmol/L hematin enhanced guaiacol peroxidase, superoxide dismutase, ascorbate peroxidase and catalase activities in wheat seedling leaves subjected to salt stress. These effects are specific for CO because the CO scavenger hemoglobin (1.2 mg/L) blocked the actions of the CO donor hematin. However, higher concentration of the CO donor (1.0μmol/L) did not alleviate dry weight and water loss of salt-stressed wheat seedlings. These results suggest that exogenous application of low levels of a CO donor may be advantageous against salinity toxicity.(Author for correspondence.Tel (Fax): 025 8439 6673；E-mail： wbshenh@njau.edu.cn)

Key words: carbon monoxide, lipid peroxidation, oxidative stress, salinity, seedling leaves, wheat.