Germination ecology of Salicornia dolichostachya and Salicornia brachystachya

A number of germination experiments was performed on seeds, collected from various populations of Salicornia dolichostachya and Salicornia brachystachya. It appeared that the germination percentage of seeds from various populations of the same species did not differ, but a significant difference in the germination percentage between the two species existed. Both species germinated best at low salinity, while the optimum germination temperature decreased when salinity increased. The order of application was important when applying fluctuating salinities to the seeds: a low salinity level followed by a high salinity level slowed down or stopped the germination irreversibly, while the opposite order resulted in a higher total germination percentage. Soil moisture content that was undersaturated had no effect on the germination of S. dolichostachya but decreased the germination of S. brachystachya significantly. Fluctuating temperature regimes had no effect on the total germination percentage but did have an effect on the germination rate. Seeds buried under a layer of sediment of 1 cm or more did germinate but the seedlings were unable to emerge. A field experiment confirmed the findings in the laboratory. The results are discussed in relation to the distribution and size of the populations of both species.