Ecophysiological Responses of Triterpene Glycosides in Buds of (Miq.) Seem. to Late Spring Frost with Soil-Mediated Effects.

Late spring frost (LSF) poses a threat to temperate forest ecosystems; however, its combined effects with soil properties on triterpene glycosides in the buds of valuable shrubs are still unclear. In this study, natural (Miq.) Seem. populations were investigated in 15 counties in Heilongjiang and Jilin provinces in Northeast China. Buds were sampled in 3-5 cm length and used for determining triterpene glycosides (TGs) of Araloside VI, Araloside V, and 4-F8 (structural analogs) in spring of 2023. LSF in Heilongjiang showed longer days reaching 20 °C (CD20) (6.0 ± 2.5 d), LSF number (NLSF) (1.8 ± 0.5 times) and duration (DLSF) (21.5 ± 5.2 d), and days of temperature rise (DTR) (15.9 ± 3.8 d) compared to Jilin (4.4 ± 0.4 d, 1.2 ± 0.4 times, 17.4 ± 3.9 d, 12.0 ± 3.3 d, respectively). Araloside VI (0.30-0.59%) was positively driven by DLSF but negatively driven by DTR. Araloside V (0.04-0.17%) and 4-F8 (0.09-0.44%) were positively influenced by the lowest temperature, DTR, and CD20, negatively influenced by NLSF, and slightly influenced by organic matter. In LSF-prone regions, soil organic matter and nutrient availability do not need to be enriched, and soil pH should be higher than 5.7 if high TGs are the objective in buds.