Long-term seed bank storage reveals interspecific variation in seed longevity of native Rhododendron species in Korea

Abstract Key message We evaluated the seed storability of three native Korean Rhododendron species ( Rhododendron micranthum Turcz., R. mucronulatum Turcz., and R. schlippenbachii Maxim.) under storage seed bank conditions. Although the three species were classified as bearing orthodox seeds, our analysis revealed a profound interspecific divergence in storability trends. These results highlight the need for species-specific storage protocols, even within the same genus or storage category. Context Rhododendron micranthum , R. mucronulatum , and R. schlippenbachii are representative native Rhododendron species in Korea. They differ genetically and ecologically. Conservation of each species is becoming critical under climate change conditions, and reliable long-term data on seed storability are essential for effective conservation planning. Aims This study aimed to obtain long-term germination data for the three species across various storage periods (>10 years) to statistically evaluate the interspecific differences in longevity and storability during seed bank storage. Methods Seeds were collected from wild populations in Korea and processed according to standardized seed bank protocols. Changes in germination were assessed using periodic germination tests. Results Seed longevity varied significantly among species ( p < 0.001), and R. micranthum exhibited a rapid decline in germination beyond 10 years. R. mucronulatum showed a more gradual decline. In contrast, R. schlippenbachii maintained a consistently high germination rate throughout the storage. Probit-based P 50 estimates supported these patterns for species exhibiting significant slopes of deterioration, whereas the longevity of highly persistent seeds remained statistically uncertain. The GLM analysis revealed a highly significant Time × Species interaction ( χ 2 = 142.01, df = 2, p < 0.001), demonstrating fundamentally different rates of germination loss despite identical storage conditions. Conclusion These findings demonstrate a strong interspecific variation in seed storability among Korean Rhododendron species. The results underscore that categorical storage designations (i.e., “orthodox”) may mask substantial differences in actual storage potential.