Interspecific competition affects spore germination and gametophyte development of mosses

Even though protonemal development of bryophytes has been well studied, it remains unknown whether interspecific competition among mosses species affects their early growth and development. This study evaluated the effects of interspecific competition on in vitro germination and gametophyte development between each pair-wise combination from six common moss species: Atrichum undulatum, Bryum argenteum, Ceratodon purpureus, Funaria hygrometrica, Hypnum cupressiforme and Leptobryum pyriforme. Two experiments were included: In the first experiment, each species was monocultured in sterile agar plates as controls, and each pair of mosses (in total 15 pair-wise combination) were cultured together in agar plates with two time intervals --- both species were sown at the same time, and one species was sown 20 days after the other---as treatments. The second experiment was based on the results of the first one: 1ml sterile water was added to the agar plate if the treatment showed significant germination difference of spores compared to the control, and then the water was collected and added to new spores to test for allelopathic effects. Each species decreased its spore germination rate in a certain way when sown with another one, and the inhibition in spore germination was stronger in treatments with 20 days interval than those with 0 day interval. For different species, the number of gametophytes per germinated spore could be higher or lower than control when sown with different species. The results indicated that spore germination is easily inhibited by interspecific competition, and it is difficult for the second species to germinate if the first one already occupies the space. The interspecific competition could inhibit or enhance the formation of gametophytes. However, no significant inhibition of spore germination was found in the second experiment, which indicated that allelopathy mediated by dissolved substances was not present or too weak to be detected in the present experimental setup. (Less)