Osmotic Adjustment of Plants to Saline Media. II. Dynamic Phase

Bernstein, Leon. (U. S. Salinity Lab., Riverside, Calif.) Osmotic adjustment of plants to saline media. II. Dynamic phase. Amer. Jour. Bot. 50(4): 360–370. Illus. 1963.—The time-course of osmotic adjustment in bean and pepper plants to increased salinity of the medium was determined by periodic sampling of plants following salt additions to the medium. Bean plants adjusted to increases of 1 atm OP within a day, the adjustment in roots occurring primarily at night following salt addition at 6 pm, whereas leaves and stems made most of their adjustment in the daytime. Pepper plants did not adjust completely to 1.5 atm NaCl additions in 48 hr, but OP increased by about the same amount in both species (0.5—1.0 atm per day). Diurnal fluctuations in OP of leaves and stems of both species and in roots of pepper were matched by parallel fluctuations in K concentrations. Added NaCl caused increased concentrations of K in leaves and stems which were more or less replaced by more slowly absorbed ions, Ca and Mg in bean leaves and Na in bean stems. Other salts produced comparable immediate effects on K level, but K was replaced more rapidly if the cation added was readily accumulated by the bean (Ca). In roots, Na uptake predominated if Na salts were added but K uptake was important on the CaCl2 treatment. The K effects suggest a passive distribution of K between the cell and the medium.