Nine naked seed stratification methods were used to treat Korean pine seeds, along with constant temperature, warm (20 ℃) to low (5 ℃) temperature, and low to diurnal variable temperature conditions (12 h at 20 ℃, 12 h at 5 ℃). Fresh, mature seeds of Korean pine were soaked in water for 5 days and disinfected, then placed in a temperature-controlled environment for stratification. Humidity was maintained at approximately 60% and the stratification period lasted for 20 weeks. During the stratification process, samples were taken every 4 weeks to measure the seed embryo length, embryo length to kernel length ratio, embryo dry weight to kernel dry weight ratio, germination percentage, germination index, mean germination time, and physiological activity of the middle seed coat and seed kernel inhibitors. The physiological activity of the inhibitors was measured with cabbage (Brassica campestris L. ssp. chinensis) seeds as the recipient plants, and the germination rate of the cabbage seeds was determined after 24 h.

①At the end of the stratification period, the 20 weeks treatments of warm temperature, diurnal variable temperature, and three different treatments of warm to low temperature, embryo length and the embryo length to kernel length ratio of Korean pine seeds were significantly increased. Under the three low temperature to diurnal variable temperature treatments, longer diurnal variable temperature stratification periods resulted in greater embryo lengths and embryo length to kernel length ratios. Embryo length and embryo length to kernel length ratios of Korean pine seeds were minimized after 20 weeks of a low temperature treatment. The warm temperature treatments, diurnal variable temperature treatments, and the three warm to low temperature treatments all resulted in embryos greater than 9 mm in length. The treatment of warm temperature for 12 weeks followed by low temperature for 8 weeks resulted in the longest embryo (10 mm), followed by the treatment of warm temperature for 8 weeks followed by low temperature for 12 weeks, which produced an embryo of 9.91 mm length. Warm temperature, diurnal variable temperature, the 4 weeks low temperature and 16 weeks diurnal variable temperature, and the three warm temperature to low temperature treatments all resulted in embryo length to kernel length ratios above 74%. The 12 weeks warm temperature and 8 weeks low temperature treatment had the largest embryo length to kernel length ratio (81.82%), followed by the 8 weeks warm temperature and 12 weeks low temperature treatment (78.62%). The embryo dry weight to kernel dry weight ratio increased following the 20 weeks of stratification for all embryos. At the end of the stratification periods, the 20 weeks warm temperature treatment and the three warm temperature to low temperature treatments resulted in embryo dry weight to kernel dry weight ratios greater than 5%. The 8 weeks warm temperature and 12 weeks low temperature treatment had the largest embryo dry weight to kernel dry weight ratio (5.83%), while the embryo dry weight to kernel dry weight ratio in the other treatments was less than 5%.②After 16 weeks of stratification, the 4 weeks warm temperature and 16 weeks low temperature treatment and the 8 weeks warm temperature and 12 weeks low temperature treatment were the only treatments with germination rates exceeding 10%; the 8 weeks warm temperature and 8 weeks low temperature treatment had the highest germination rate (25%). Twenty weeks of stratification increased the germination percentage of the three warm temperature to low temperature treatments significantly, but the germination percentage of the other treatments was less than 10%, and some did not germinate. Among these treatments, the 12 weeks warm temperature treatment, followed by 8 weeks low temperature treatment yielded the highest germination percentage (57.0%)； next，the 8 weeks warm temperature treatment followed by 12 weeks low temperature treatment, with a germination percentage of 54%. At the end of the stratification period, although the germination percentage of the 8 weeks warm, 12 weeks low temperature treatment was slightly lower than that of the 12 weeks warm, 8 weeks low temperature treatment, the germination index of the former was significantly higher than that of the latter, and the mean germination time was shortest for the former.③After 20 weeks of stratification, the inhibitor activity of the middle seed coat extract decreased significantly, but the inhibitor activity of the kernel remained strong. The germination percentage of the cabbage seeds in the middle seed coat extract for each stratification treatment was as low as 33%, but germination was effectively eliminated in the seed kernel extract.④Significant positive correlations were observed between Rorean pineseed germination percentage and embryo length, as well as between seed germination rate and embryo dry weight to kernel dry weight ratio. No significant correlation was observed between embryo length to kernel length ratio and inhibitory activity and Korean pine seed germination percentage.

The warm temperature treatment was conducive to the ripening growth of Korean pine seeds, and the low temperature treatment was beneficial to the release of physiological dormancy. The optimal germination percentage was achieved by stratification treatment at warm temperature for 8 weeks, followed by low temperature for 12 weeks.