Effects of salt stress on root plasma membrane characteristics of salt-tolerant and salt-sensitive buffalograss clones

To test the hypothesis that differences in plasma membrane chemical characters exist between a salt-tolerant and a salt-sensitive buffalograss clone, plasma membrane H+-ATPase activity, membrane phospholipid composition, and corresponding fatty acyl chains were studied for root plasma membrane of two buffalograss (Buchloe dactyloides (Nutt.)) clones, Salt stress caused greater reductions of plasma membrane H+-ATPase activity and total plasma membrane protein concentration in the salt-sensitive buffalograss clone than in the salt-tolerant clone. Salt stress also reduced the amount of plasma membrane phospholipid per gram fresh weight. Fatty acyl chains derived from five phospholipids including phosphatidyl ethanolamine (PE), phosphatidyl glycerol (PG), phosphatidyl choline (PC), phosphatidyl serine (PS) and phosphatidyl inositol (PI) were determined. Salt stress caused a greater reduction, especially of the strong anionic phospholipids (PS and PI), in the salt-sensitive clone than in the salt-tolerant clone. Under conditions without salt stress, the unsaturated fatty acids including C14:1, C18:1 and C18:3 found in the salt-tolerant clone were not detected in the salt-sensitive clone. A double bond index (DBI) (number of double bonds per mole) was used to measure the degree of unsaturation of fatty acids. Under conditions without salt stress, the salt tolerant clone had a DBI of 0.23. Salt stress caused a greater increase of DBI in the salt-tolerant clone than in the salt-sensitive one. The present study documented a difference in salt stress response at the plasma membrane lipid metabolism level between salt tolerant and salt-sensitive buffalograss clones. These plasma membrane chemical characteristics may be at least partially responsible for the salt-tolerance in this species.