Abstract:

In order to explore the morphological characteristics and germination characteristics of Rhododendron species, the morphological structures of seeds from eight species were observed using a stereo microscope (LIOO SZ745). We also explored the impacts of gibberellin (GA₃) concentration, GA₃ treatment time, and soaking time in water on the germination traits of Rhododendron species. Additionally, we conducted a comparative analysis of germination traits among different species and provenances of Rhododendron species, as well as the impact of seed size on germination. The results showed that: (1) the seeds of the Rhododendronspecies were spindle-shaped, oval and small, the longitudinal and the aspect ratio of R. micranthum seeds was significantly higher than the other three Rhododendron seeds, the transverse diameter of the R. molle seeds was significantly higher than the other three Rhododendron seeds (P<0.01). (2) R. micranthum had the highest germination rate at GA₃ 0 mg/L, 4 h in the processing time, and the soaking time of 24 h; R. simsii seed was the highest in germination rate at GA₃ 100 mg/L, the processing time was 12 h, and the soaking time was 48 h; when the GA₃ 400 mg/L, the processing time was 4 h, the soaking time was 24 h, the germination rate of the R. mucronulatum was the highest; when the GA₃ 0 mg/L, the processing time was 4 h, the soaking time was 48 h, the germination rate of R. molle was the highest. (3) There were differences in germination rate, germination potential, germination lag, germination peak, germination duration and germination index of Rhododendron seeds among different provenances. R. simsii had the highest germination rate and germination potential, R. mucronulatum had the longest germination lag, germination peak and germination duration, and R. molle had the largest germination index. (4) The longitudinal diameter, transverse diameter and aspect ratio of Rhododendron seeds were negatively correlated with germination rate, germination potential, germination time lag, germination peak period, germination duration and germination index. This study can provide a theoretical basis for species identification and introduction and propagation of Rhododendron plants.

Key words: Rhododendron, seed morphology, germinating characteristics, provenance, gibberellin, orthogonal test