Salt tolerance in Salicornia

Salinization of agricultural land is an increasing problem. Because of their high tolerance to salinity, Salicornia spp. could become model species to study salt tolerance. Moreover, they also represent promising saline crops. The salinity-growth response curve for Salicornia dolichostachya Moss was evaluated at 10 different salt concentrations in a hydroponic study in a greenhouse and at 5 different seawater dilutions in an outside setting. Salt concentrations ranged between 0 mM and 500 mM NaCl (≈ seawater salinity). Plants were grown for six weeks, and morphological and physiological adaptations in different plant parts were evaluated. S. dolichostachya had its growth optimum in the range between 100 and 300 mM NaCl in the root medium, independent of the basis on which growth was expressed. The relative growth rate (RGR) in the greenhouse experiment was comparable with RGR-values in the outdoor growth-experiment. Leaf succulence and stem diameter had the highest values at the growth optimum (300 mM NaCl). Carbon isotope discrimination (δ 13 C) decreased upon salinity. S. dolichostachya maintained a lower leaf sap osmotic potential relative to the external solution over the entire salinity range, this was mainly accomplished by accumulation of Na + and Cl – . Glycine betaine concentrations did not significantly differ between the treatments. Na + :K + -ratio and K + -selectivity in the shoots increased with increasing salinity, both showed variation between expanding and expanded shoot parts. I concluded that S. dolichostachya is highly salt tolerant and showed salt requirement for