Effects on NaCI on ion relations and carbohydrate status of roots and on osmotic regulation of roots and shoots of <em>Atriplex amnicola</em>.

Atriplex amnicola was grown at 25, 200 or 400 mol m^-3 NaCl. Root tissues at different stages of development were investigated for concentrations of K⁺, Na⁺ and Mg²⁺, and in some cases for Cl^-. Sugar and starch concentrations were measured for plants grown at 25 or 400 mol m^-3 NaCl. In the 'slightly vacuolated' root tips, Na⁺ was only 40 mol m^-3 at an external concentration of 400 mol m^-3 NaCl. The concentrations of K⁺ were not affected substantially by external NaCl between 25 mol m^-3 and 400 mol m^-3. The 'highly vacuolated' root tissues had substantially higher concentrations of K⁺, Na⁺ and Cl^- in plants grown at 200 and 400 mol m^-3 NaCl than in plants grown at 25 mol m^-3 NaCl. Concentrations of Cl^- and of the sum of the cations in recently expanded tissue were similar to those in the bulk of the roots, consisting mainly of old cells. However, the K⁺:Na⁺ decreased with age; at 400 mol m^-3 external NaCl with a K⁺:Na⁺ of 0.012, the K⁺:Na⁺ in recently expanded 12 mm root tips was as high as 1.6, compared with 0.7 for the bulk of the roots. These ion data were used to estimate cytoplasmic and vacuolar concentrations of K⁺ and Na⁺. Such calculations indicated that between 25 mol m^-3 and 400 mol m^-3 external NaCl the concentration of the sum of (Na⁺ + K⁺) in the cytoplasm was maintained at about 180-200 mol m^-3 (cell water basis). In contrast, the (Na⁺ + K⁺) concentration in the vacuole was 170 mol m^-3 for plants grown at 25 mol m^-3 NaCl and 420 mol m^-3 for plants grown at 400 mol m^-3 NaCl. The expanding root tissues exhibited greatly decreased solu... [ABSTRACT FROM AUTHOR]