Studies on Action Mechanism and Effects of Uniconazole (S-3307) on Cold Resistance of Rice Seedlings

The effect of soaking seeds in uniconazole (S-3307) solution of different concentration on cold resistance of rice seedlings was studied under different seeding dates. The results showed that soaking seeds in S-3307 significantly decreased the dead seedling percentage and stagheaded seedling percentage under the usual seeding time of production, and the treatment of 20 mg/L of S-3307 solution showed the best effect. Its mechanism of cold resistance was that S-3307 increased the activities of SOD, POD, and CAT, and decreased the content of MDA (the products of membrane lipid peroxidation) and ion leakage. And it also increased free proline content of seedlings (the metabolits of rice seedlings), thus alleviating the water deficiency of seedlings under cold stress.