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Salinization of agricultural land is an increasing problem. Because of
their high tolerance to salinity, Salicornia spp. could become models to
study salt tolerance; they also represent promising saline crops. The
salinity-growth response curve for Salicornia dolichostachya Moss was
evaluated at 12 salt concentrations in a hydroponic study in a greenhouse
and at 5 different seawater dilutions in an outside setting. Salt
concentrations ranged between 0mM and 500mM NaCl (~seawater salinity).
Plants were grown for six weeks and morphological and physiological
adaptations in different tissues were evaluated. S. dolichostachya had its
growth optimum at 300mM 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 (300mM NaCl). Carbon isotope discrimination (@d^1^3C)
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 tissue. We conclude that S. dolichostachya was highly salt
tolerant and showed salt requirement for optimal growth. Future growth
experiments should be done under standardized conditions and more work at
the tissue and cellular level needs to be done to identify the underlying
mechanisms of salt tolerance.
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