SOLUTE POTENTIAL AND CYTOPLASMIC VISCOSITY IN TRITICUM-AESTIVUM AND HORDEUM-VULGARE UNDER SALT STRESS - A COMPARISON OF SALT-RESISTANT AND SALT-SENSITIVE LINES AND CULTIVARS

Cell solute potential and cytoplasmic viscosity in four lines of wheat (Triticum aestivum L.) and two cultivars of barley (Hordeum vulgare L.) differing in their relative salt resistance were investigated. Seedlings were grown in 1/4-strength Hoagland solution with and without 100 mM NaCl (219 mOsm; for Hordeum, additionally isosmolal polyethylene glycol 10,000). Solute potential (PSI(s)) and cytoplasmic viscosity of leaf sheath subepidermal cells (Triticum) and solute potential of coleoptile subepidermal cells (Hordeum) were measured by the plasmolytic method and by centrifugation, respectively. NaCl decreased PSI(s) in all lines and cultivars tested and more so in Hordeum than in Triticum. In salt resistant seedlings the difference in PSI(s) between cells from control and salt treated plants was smaller than in salt sensitive seedlings but always exceeded the lowering of PSI(s) of the growth medium by NaCl. For PEG treatment the PSI(s) decrease corresponded to the decrease of PSI(s) in the solution (osmotic adjustment). Salt resistant lines had a high cytoplasmic viscosity that increased under NaCl stress. In salt sensitive lines viscosity was low and decreased further with NaCl addition. The results confirm that the deleterious effect of salinity is not attributable to osmitic stress alone and that the cytoplasm itself is significantly different for salt resistant and salt sensitive cultivars.