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

摘要

This work examines the responses of faba beans to the external K~+/Na~+ ratio, the role of inorganic ions Na~+, K~+, Ca~(2+), Mg~(2+), Cl~-, PO_4~(3-) and SO_4~(2-), the role of organic solutes, amino acids, soluble proteins and soluble sugars. The plants were treated with 25 mM solutions of NaCl and KC1 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~+, Ca~(2+) and Cl" to readjust their osmotic pressure and decrease their Mg~(2+) content. Stems were dependent on Na~+, Ca~(2+) and Cl" while roots were dependent on Mg~(2+) more than other organs. Leaves and stems increased their PO_4~(3-) 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 leaves' amino acid and soluble protein contents.