Absorption and Transport of Water and Ions in Corn and Sunflower Plants Grown Under Saline Conditions

In order to analyze absorption and transport of water and ions in plants affecting the salinization in the root zone through physical and physiological processes, we measured water and ion uptake by roots, transpiration rate, leaf conductance, and ion concentrations in root xylem sap and other plant tissues of corn and sunflower grown under saline conditions using a nutrient film technique system. The rate of root water uptake was lower in corn than in sunflower, where the daytime stomatal closure in response to the excessive water stress induced by the saline solution was occurred in corn but not in sunflower. NO₃^-, PO₄^3- and K⁺ were highly concentrated in the xylem sap as a result of the active and selective uptake of nutrients by roots of both corn and sunflower. Na⁺, which is not an essential element for plant growth, was not highly concentrated in the xylem sap or plant tissues of corn because corn exhibited a poor Na⁺ absorption and transportation ability. On the other hand, sunflower had a greater ability to absorb water, Na⁺, Mg²⁺, Ca²⁺, Cl^-, and SO₄^2-, and to transport these ions from the roots to the shoot. These differences in absorption and transport of water and ions indicate that sunflower is more salt tolerant than corn. The effects of these absorption and transport characteristics on plant growth and soil salinity should be taken into account for sustainable and effective plant production in salinized crop fields.