Effects of long-term salinity on the growth of the halophyte Spartina alterniflora Loisel

Abstract

The effects of salt stress on the growth of Spartina alterniflora were investigated by imposing seven levels of salt stress (0, 100, 200, 300, 400, 500, and 600 mM NaCl) on potted plants. The seedlings were grown in vermiculite in a greenhouse for six months. Optimal growth of S. alterniflora occurred at salinity levels of 100 and 200 mM NaCl. Seedlings grew less in freshwater conditions than in the 100 and 200 mM NaCl treatments. Higher levels of salinity (300 to 600 mM NaCl) caused a reduction in shoot number, height, biomass accumulation and leaf area. However, salt treatment resulted in only small changes in leaf water content. Although, chlorophyll concentrations were significantly higher at 100 and 200 mM NaCl than other salinity levels, photosynthetic rates were overall quite high regardless of treatment, ranging from 44.65 to 50.88 μmol m^-2 S^-1 of carbon gain. The results indicate that S. alterniflora has high tolerance to salt, and lower salt concentrations stimulate its growth.

Key words: Spartina alterniflora, salt stress, biomass production, chlorophyll concentration, water content, photosynthetic rates, stomatal conductance.