Abstract: Seed germination is a critical phase for plant population establishment and expansion, regulated by multiple factors. We investigated the effects of storage temperature, incubation temperature, substrate type, and mixed-sowing ratio on seed germination of Phragmites australis and Triarrhena lutarioriparia. Utilizing seed germination assays and allelopathy bioassays, we measured germination percentage, germination vigor, germination index, root length, shoot length, branch number, vital index, and the synthetic effect of allelopathy (SE). The results showed that low-temperature storage at 4 ℃ significantly enhanced germination of both species by breaking seed dormancy. The optimal temperature for seed germination of both species was 30 ℃. Furthermore, loam soil and monoculture conditions were more conductive to the germination of both species, while mixed sowing intensified the competition. The higher germination rate was observed when the higher proportions of a single species under mixed sowing conditions. Under the extract concentrations of 0.025 and 0.05 g·mL^-1, the SE of P. australis extract on T. lutarioriparia seeds was both -0.17, whereas the SE of T. lutarioriparia extract on P. australis seeds were -0.28 and -0.46, respectively. The extract of P. australis and T. lutarioriparia exhibited inhibitory effects on seed germination, with the allelopathic intensity of T. lutarioriparia extract on P. australis seeds being significantly stronger than that of P. australis extract on T. lutarioriparia seeds. Our results indicated that the integrated mechanisms involving temperature treatments, substrate adaptation and interspecific interactions variously drive the germination of P. australis and T. lutarioriparia, providing critical ecological evidence to decipher the spatial differentiation patterns of natural populations.

Key words: Phragmites australis, Triarrhena lutarioriparia, extract, temperature, mixed sowing, allelopathy