Influences of salinity and light on germination of three Sarcocornia taxa with contrasted habitats

We analysed the responses of seeds of three closely related halophytic taxa of the genus Sarcocornia in contrasted habitats, Sarcocornia perennis (low marsh), Sarcocornia fruticosa (high marsh) and S. perennis x fruticosa (middle marsh), to different salinity concentrations (0, 2, 4 and 6%) and light regime (light/dark and dark). Germination reflected their position in the tidal gradient, showing higher percentages at hypersalinity those taxa colonising upper positions (c. 40%). S. fruticosa showed germination in darkness and it accelerated its germination after prolonged salinity exposure. S. perennis x fruticosa presented intermediate responses, sharing the capacity of germinating in hypersaline conditions with S. fruticosa and the absence of germination in darkness and the absence of acceleration of germination with S. perennis. Finally, we recorded common germination behaviours for the three taxa: short germination periods, reduction of final germination percentage, enforcing of seed dormancy and reduction of seed viability by increasing salinity. Germination responses to salinity of the three Sarcocornia seem likely to influence their colonisation capacities down the tidal gradient and hence may be important in the maintenance of taxa zonation in salt marshes. (C) 2004 Elsevier B.V. All rights reserved.