EFFECT OF SODIUM-CHLORIDE ON GROWTH, ION CONTENT, AND HYDROGEN-ION EXTRUSION ACTIVITY OF SUNFLOWER AND JOJOBA ROOTS

The effect of sodium chloride (NaCl) on growth, internal ion content, and proton release of sunflower (Helianthus annuus L. cv. Enano) and jojoba [Simmondsia chinensis (Link) Schneid.] roots was studied in order to understand the relationship between the above parameters and salt tolerance. The increase in sodium (Na) ions concentration and the decrease in calcium (Ca) ion concentration in sunflower roots grown in the presence of 50 mM NaCl, relative to control without added NaCl, run parallel to the reduction in growth capacity and in hydrogen (H) ion extrusion activity. However, while the rate of growth was not affected by the addition of Ca to a culture medium containing 50 mM NaCl, H-ion extrusion activity was reversed, reaching a similar value to that of the roots cultivated in deionized water or in 25 mM NaCl. In jojoba, a reduction of root growth at 100 and 150 mM NaCl was observed, while no significant effects on Ca and potassium (K) contents and on H-ion extrusion activity were found. These results indicate that proton extrusion and Ca concentration could probably be correlated with sunflower root growth. Moreover, in jojoba roots the lack of a clear correlation between growth, Ca content, and proton extrusion suggest a response to NaCl treatments at a relatively low and stable rate of physiological functions rather than an active mechanism being involved.