Rapid Osmotic Adjustment by a Succulent Halophyte to Saline Shock

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Abstract
The short term osmotic adjustment of Salicornia europaea L. spp. rubra (A. Nels) Breitung when suddenly exposed to 100 mM NaCl was measured. Plants were grown hydroponically, shocked with 100 mM NaCl added to the culture solution, and stem tips analyzed for free inorganic ions and small organic molecules at intervals up to 72 h. In the 1st 2 h, the calculated leaf osmoticum showed a net increase of 158.8 mM most of which was free Mg2+ (+135.3 mM). Total sugars increased almost 5-fold by the 6th h, enough to provide sufficient osmoticum for the cytoplasm if only partially confined there. By 24 h, all measured osmotica had decreased except Na+, Mg2+, Cl-, and proline, with the net increase being 208 mM. By 72 h, there was a net gain of 356 mM in osmotica of the stem tips, due to Na+ (+233.3 mM), Cl- (+306.7 mM), and a small increase in sugar and proline (+3, 5 mM), with all other osmotica decreasing in concentration. Compatible osmotica did not change sufficiently to account for osmotic balance between vacuole and cytoplasm; consequently, there must have been a reapportionment of osmotica within the cell in the short time duration of this experiment.