Germination responses to salt stress of two intertidal populations of the perennial glasswort Sarcocornia ambigua

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Sarcocornia ambigua is a perennial halophyte of the Atlantic coast of South America. The species occurs in salt marshes and mangrove swamps and is able to grow under hypersaline conditions. S. ambigua seeds were collected from two intertidal populations located inside and at the entrance of the Patos Lagoon estuary (RS, Brazil). The seeds were germinated by incubation for 22 days in 0, 5, 15, 30 and 45g NaClL−1 solutions at 20–30°C and with a 12:12h photoperiod. There were no significant differences in germination between S. ambigua populations. High average germination (81–84%) occurred at low salinities (0 and 5g NaClL−1) and decreased at salinities of 15g NaClL−1 (41–46%) and above. Seeds were able to germinate (3%) even in 45g NaClL−1. Both populations of S. ambigua demonstrated an inhibition of germination under saline conditions. This inhibition was reversible through removal of the salt stress. The percentage of unviable seeds increased from 4% to 11–18% as the salinity increased from 5 to 15–40g NaClL−1. The germinative responses to salinity of S. ambigua are typical of an extreme halophyte. The predominant outflow tendency of the waters in the study area and the choked morphology of Patos Lagoon favour the flux of seeds between marshes in the middle estuary and at the narrow estuarine inlet, preventing local differentiation of S. ambigua populations.