K+/Na+ soil-plant interactions during low salt stress and their role in osmotic adjustment in faba beans

Abstract

This work examines the responses of faba beans to the external K+/Na+ ratio, the role of inorganic ions Na+, K+, Ca2+, Mg2+, Cl-, H3PO4 and H2SO4, the role of organic solutes, amino acids, soluble proteins and soluble sugars. The plants were treated with 25 mM solutions of NaCl and KCl at 0, 0.425, 1.134, 2.55 and 6.8 K+/Na+ ratios. The different organs of treated plants showed different responses. Leaves were dependent on K+, Na+, Ca2+ and Cl- to readjust their osmotic pressure and decrease their Mg2+ content. Stems were dependent on Na+, Ca2+ and Cl- while roots were dependent on Mg2+ more than other organs. Leaves and stems increased their H3PO4 contents with the increase in external K+. Soluble sugars played the most important role, as organic solutes, in osmotic readjustment. With the increase in external K+ the dependence of roots on soluble sugars decreased. The increase in external K+ increased the leavesamino acid and soluble protein contents.