Salt stress response in the halophyte Limoniastrum guyonianum Boiss

• Limoniastrum guyonianum is a facultative halophyte.
• Fresh weight increase was associated with stimulation of photosynthetic activity.
• L. guyonianum maintained an adequate osmotic adjustment up to 400 mM NaCl.
• L. guyonianum is efficient at using the low available water under salt stress.
• Salt excretion was poorly selective, Cl− and Na+ were the prominent excreted ions.
• Chloroplast ultrastructure was highly preserved under 300 mM NaCl.

Limoniastrum guyonianum is an evergreen perennial halophyte. Its response to severe salinity was investigated by exposing ninety-day-old plantlets to a 0–1000 mM NaCl range for 3 months. Growth, water status, electrolyte leakage (EL), malondialdehyde (MDA) content, salt excretion, leaf pigment content, photosynthetic parameters, chloroplast ultrastructure, and contents of Na+, Cl−, K+, Ca2+, Mg2+, proline and polyphenols were determined. Results of these studies indicate that L. guyonianum is a facultative halophyte and can survive at 1000 mM NaCl. Plants treated with 300 mM NaCl had a 25% increase in whole plant fresh mass that is attributed to increased photosynthetic activity and adequate water uptake. Sodium and chloride accumulation increased with salinity and was associated with significant reductions in leaf K+, Ca2+ and Mg2+ concentrations due to excretion out of leaves. Consequently, photosynthetic machinery was highly preserved against toxic ions. Polyphenol accumulation increased with salt treatments while lipid peroxidation decreased with salinity levels at 200–1000 mM NaCl. Proline accumulation increased with salt treatments up to and including 400 mM NaCl. The increase in intrinsic water use efficiency at medium salt levels indicates that L. guyonianum is efficient at using the low available water under salt stress. These physiological and biochemical responses to salinity and the salt excretion process allowed L. guyonianum to tolerate severe salinity.