Factors Associated with Determination of Root 22Na+ Influx in the Salt Accumulation Halophyte Suaeda maritima

Salinity is an increasing problem for agricultural production worldwide. The result of low-affinity Na+ uptake is toxic to the cytoplasm of most crop plants. Nevertheless, the pathways for this low-affinity Na+ uptake are still uncertain. In this work we used Na-22(+) isotope tracing technology to investigate factors associated with determination of root Na-22(+) influx in the salt accumulation halophyte Suaeda maritima. We found that a 2 min of exposure to the Na-22(+) labeled uptake solution was optimal for determining Na-22(+) influx into excised roots of S. maritima and that 7 min of blotting is suitable in Na-22(+) influx experiments. Na-22(+) influx did not increase linearly with the increasing external Na+ concentration, in the range tested, of 2 to 300 mM NaCl. But root Na-22(+) influx and root Na+ concentration were well correlated. Na-22(+) influx into excised roots of S. maritima was not, however, well correlated with the plant size. All the above results indicated further that this Na-22(+) isotope influx procedure is a good method for quantify Na+ uptake rate by the roots of the salt accumulation halophyte.