Stress Metabolism. VII. Salinity and Proline Accumulation in Barley

Abstract

Barley plants (cv. Prior) were grown in nutrient culture and subjected to a variety of salinity stress treatments when 10-12 days old. Salinity stress was either imposed abruptly by transferring plants to a solution containing NaCl of - 5.7 or - 10.7 bar osmotic potential, or gradually by transferring plants daily to solutions of successively lower osmotic potential (- 1 bar per day). Prolonged exposure to salinity stress was achieved by holding plants in a - 10.7 bar osmotic potential solution for 6 days. Proline accumulated rapidly in plants subjected to a salinity stress greater than - 5.7 bar osmotic potential. Accumulation appeared to be controlled by tissue osmotic potential rather than by turgor, and continued for 24 h after the saline solution was removed from the root medium. Proline accumulation continued for at least 3 days in plants held at - 10.7 bar osmotic potential, during which time the plants continued to grow slowly. The accumulated proline made only a minor contribution to osmotic regulation in the plant,