Abstract
The effects of different salinities on the germination of Spartina ciliata seeds were tested during 40 days in the laboratory, using six concentrations of NaCl (0,45, 80, 130, 170 and 215 mM) besides three concentrations of seawater (25,30 and 35‰). In addition, the survival and growth of seedlings were tested in five constant salinity regimes (0,45, 80 and 170 mM NaCl) as well as in five regimes of simulating seawater overwash. The results showed that seeds possed a high germination capacity over a wide range of salinities (0 to 215 mM NaCl). Although concentrations close to full-strength seawater completely inhibited seed germination, the transfer of the ungerminated seeds to freshwater immediately stimulated this. The effects of salinity on seedling growth showed that shoot height and root length were the variables most sensitive to salt stress. Frequent overwash with seawater significantly reduced the survival and growth of Spartina ciliata seedlings. The success in seed germination, survival, and growth of Spartina ciliata in salinities above those normally found in the natural environment could explain the species being distributed throughout salt-stressed foredune habitats in southern Brazil.
Highlights
Substrate salinity is one of the environmental factors that sand dune plants may encounter during their life cycles
Seed germination - Seeds were surface sterilized in 1.25% sodium hypochlorite solutions for 15 min (Seneca 1969), rinsed with distilled water, and sown on two layers of filter paper (Whatman no. 1) in 9-cm Petri dishes wetted with 5ml of O, 45, 80, 130, 170 and 215mM NaCI solutions
Coastal dune plants are exposed to varying amounts of salt, from complete immersion in seawater during storm tides, to occasional salt spray (Cordazzo 1994)
Summary
Substrate salinity is one of the environmental factors that sand dune plants may encounter during their life cycles. Substrate salinity .can act as a major selective force, determining seed germination, seedling establishment and survi vaI in coastal areas (Barbour 1970; Seneca 1972; Ungar 1978). 1977; Greenway & Munns 1980; Grattan & Grieve 1993) The consequences of these complex effects are the reduction in leaf size, internode, and culm length, leading to a miniaturization of saIt marsh and sand dune plants (Blits & Gallagher 1991; Cordazzo 1994). Seed germination and seedling establishment under various salinities have been investigated in many halophytes (Ungar 1962, 1974; Bazzaz 1973; Woodell 1985), and in some sand dune species (Seneca 1969; Sykes & Wilson 1989; Greipsson & Davy 1994,). The aim ofthis study was to examine the effects of salinity on seed germination, seedling growth and the survival of S. dUata
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