Influence of water stress and abscisic acid on free proline accumulation in barley leaves

Rapid accumulation of free proline was found in barley leaves under conditions of osmotic stress at the level of -8.3 bars, but not before 9 days of its duration. The threshold value of osmotic stress for the start of a rapid accumulation of proline was about -6 bars. The excised leaves of barley subjected to water stress by wilting accumulated free proline more rapidly. In the course of 24 hours free proline content increased about 30-fold, while the water content in the leaves decreased 3-fold only. We found also that excised barley leaves with full turgor treated with abscisic acid (10-4 M) accumulated free proline as early as after 3 hours and subsequently after 24 hours free proline content increased 10-fold