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.