Germination and Physiological Characteristics of Phoebe bournei and Phoebe zhennan Seeds During Sand-stored Stratification at Different Temperatures

The seeds of Phoebe bournei and Phoebe zhennan (precious tree species) are characterized by hard seed coats and physiological dormancy. To investigate the effects of sand stratification at different temperatures (16 ℃ and 4 ℃) on seed germination and physiological characteristics of these two species, this study used their seeds as experimental materials. Indicators including germination rate, storage substance content, and antioxidant capacity were determined during sand stratification. The objectives were to identify effective stratification methods for breaking seed dormancy and to explore the physiological and biochemical changes during dormancy release. The results showed that the maximum germination rates of P. bournei seeds under warm (16 ℃) and cold (4 ℃) stratification reached 86.7% and 62.5%, respectively,, while those of P. zhennan seeds were 93.3% and 72.5%. These rates were significantly higher than those of non-stratified seeds, which were 12.5%（P. bournei）and 57.5%（P. zhennan）, respectively. Starch（ST）content in both species decreased in a stepwise pattern. Soluble protein（SP）content declined sharply from 0 to 25 days before leveling off. Under 16°C stratification, both ST and SP consumption exceeded those at 4°C. The soluble sugar（SS）content was substantially consumed at 100 days of stratification. Antioxidant enzyme activities reached higher levels during the mid-to-late stratification phase. Superoxide dismutase（SOD） and peroxidase（POD）activities exhibited sustained increases followed by decreases, showing a highly significant positive correlation. Catalase（CAT）activity initially declined and was significantly negatively correlated with malondialdehyde（MDA）content. Germination rates during stratification showed significant correlations with stratification duration and stored substances. In summary, Stratification treatment can effectively improve seed germination rate, with warm-temperature stratification showing better dormancy-breaking efficiency than cold stratification. Under identical initial conditions, P. zhennan seeds exhibited significantly higher germination rates than P. bournei, though this gap narrowed during the middle and late stratification phases. At 16°C stratification, the conversion rate of primary storage substances was higher than at 4°C, better supporting material and energy supply during seed germination. Seeds of both species exhibited higher germination rates and stronger antioxidant enzyme activity after sand-stratification for 75–100 days. Sowing seeds within this period, supplemented with appropriate cultivation management, can effectively improve seedling emergence rates.