Foliar Chloride Accumulation Overtime in Soybean Under Salt Stress.

Chloride (Cl^-) inclusion in roots and transport to shoots in soybean impose physiological stress causing foliar chlorosis and scorch, plant stunting, and even whole plant death. While the mechanism for salt tolerance in soybean is not clear, there are differences in plant response among soybean genotypes. Chloride accumulation in leaves is a common indicator for salt stress response in soybean; salt-tolerant lines are classified as Cl^- excluder while salt sensitive lines as Cl^- includer. However, the salt tolerant type will eventually die when exposed to salt stress for a long period time. The objectives of this study were to monitor the changes of leave Cl^- content over time in both Cl^- excluder and includer genotypes and to determine the threshold for duration of salt treatment for genotypic and phenotypic differentiation in a salt screen, and threshold of Cl^- concentration in leaves for foliar salt injury symptoms and plant death to occur. Three Cl^- excluders (Osage, S-100, Lee 68) and three Cl^- includers (Glenn, Dare, Clark) were treated with 120mM NaCl, 120mM KCl, and tap water for 2 hours per day for up to six weeks. The treatment was imposed beginning at the V1 stage and continued until the whole plant died. The leave samples were collected every two days after the initiation of salt treatment. Chloride concentrations were measured using the ICP-OES method. The results will be summarized and presented when the experiment is completed.