The effect of three osmotic agents on free proline and amino acid pools in Atriplex canescens and Hilaria jamesii

Abstract
Three commonly used osmotic agents, mannitol, sucrose, and polyethylene glycol 4000, were used to simulate water stress in two arid region plant species, Hilaria jamesii (Torr.) Benth. and Atriplex canescens (Pursh) Nutt. Large amounts of mannitol (300-1400 .mu.mol/g dry wt.) and sucrose (450-660 .mu.mol/g dry wt.) were absorbed by both plant species, while insignificant amounts of polyethylene glycol 4000 were absorbed. During osmotic stress, Hilaria jamesii accumulated large quantities of proline, while A. canescens accumulated only a small amount. Shoot proline content of both species varied significantly with the osmotic agents used to simulate water stress. These results indicate that use of absorbable osmotic agents to simulate water stress may have important metabolic effects on the concentration of free proline and other metabolites.