Effect of Ca²⁺ on Na⁺ and Cl^- uptake and transport in soybean root under high NaCl stress

Abstract

Two experiments were conducted. Firstly, the quantity of Na⁺ and Cl^- contents in 5-day-old soybean roots were measured during the initial 9h when the roots were immersed in 50 mmol/l NaCl solution and 50 mmol/l NaCl solution with small amount of CaCl₂ (0.5, 1.0 and 2.0 mmol/l). Secondly, suction (20kPa) was applied to the cross section of detopped soybean roots and the exudation collected for 9h and the volume was measured.
The resulting, Na⁺ content in the roots immersed in 50 immol/l NaCl and 50 mmol/l NaCl + 0.5 mmol/l CaCl2 solution for 9h was about 58 μ molg^-1_F.W. and 20 μ molg^-1_F.W., respectively. This implies that Ca²⁺ controls the K channel of cell membranes in the roots. On the other hand. Ca²⁺ did not effect Cl^- content in the roots. In addition, exudation volume was controlled osmotic pressure gradient between solution contained in the roots and the outside solution, if Ca²⁺ could maintain the ion permeability of cell membrane under 50 mmol/l NaCl solution.