Stress Metabolism. VIII. Specific Ion Effects on Proline Accumulation in Barley

Abstract

Intact 12-day-old barley (cv. Prior) plants or first-leaf sections were grown on iso-osmotic solutions of polyethylene glycol or a variety of inorganic salts for 24 h. All solutions caused a similar decline in leaf water potential with external osmotic potential in the intact plant, but the decline in internal osmotic potential was least on solutions of polyethylene glycol, causing a loss of turgor in plants growing on that osmoticurn. Plants growing on solutions of NaCl, KCl, Na₂SO₄ or CaCl, accumulated less proline than plants on iso-osmotic solutions of polyethylene glycol, but plants on MgCl₂, solutions accumulated as much or more. With leaf sections, no proline accumulated on solutions containing the monovalent cations, whereas tissue floated on salt solutions containing Mg²⁺ or Ca²⁺ accumulated as much or more proline as that on iso-osmotic solutions of polyethylene glycol. NaCl was found to inhibit the proline accumulation caused by a reduction in external osmotic potential.