Germination Characteristics and Interspecific Variation in Seeds of Three <i>Rhododendron</i> Species Native to Korea

This study aimed to clarify the germination characteristics and seed dormancy type of three Rhododendron species (R. brachycarpum, R. micranthum, and R. mucronulatum var. ciliatum) native to Korea. The embryos of three Rhododendron species were linear and fully developed, indicating the absence of morphological dormancy (MD). R. brachycarpum and R. micranthum had non-dormant (ND) seeds at dispersal, whereas R. mucronulatum var. ciliatum seeds had some physiological dormancy (PD) at population level. The application of exogenous gibberellic acid (GA3) at 1,000 mg･L-1 broke the PD of R. mucronulatum var. ciliatum, while cold stratification at 4°C had no effect on seed dormancy. The optimal environmental conditions for seed germination were light･ 25/15°C for R. brachycarpum, darkness･20/10°C for R. micranthum, and light·25/15°C for R. mucronulatum var. ciliatum. Due to the interspecific variation of Rhododendron genus, the seed dormancy type or germination characteristics of all species were distinguished in this study. This study could be useful to understand the ecophysiological characteristics of Rhododendron species native to Korea.