Effects of exogenous fatty acids on H+-ATPase activity and lipid composition of plasma membrane vesicles isolated from roots of barley seedlings under salt stress

The effects of exogenous fatty acids of different saturaturation degrees on the H+-ATPase activity and lipid composition of the plasma membrane (PM) v esicles isolated from the roots of two barley cultivars differing in salt-s ensitivity (Jian 4, salt-tolerant; Kepin 7, salt-sensitive) were investigat ed under 100 mmol L-1 NaCl stress for 2 days. The PM vesicles with high pur ity were prepared by discontinuous sucrose density gradient centrifugation. The HC-ATPase activities, phospholipid contents and the index of unsaturat ed fatty acids (IUFA) increased in the PM vesicles isolated from the roots of seedlings of two barley cultivars under NaCl stress. However, there was no obvious change in the IUFA value with exogenous fatty acids of different saturation degrees. Exogenous stearic acid and linoleic acid increased the Ht ATPase activities and phospholipid contents, bur their effects on galac tolipid contents of the PM of Kepin 7 were different. For Jian 4, treated w ith linoleic acid, the galactolipid content increased by 115.85%; the PM H-ATPase activity and phospholipid contents increased slightly. This is cons istent with the lower Na+ content and Na+/K+ ratio in leaves of salt-tolera nt Jian 4 under salt stress.