H+ ATPase activity of tonoplast in roots of Hordeum vulgare L. cv.“Tanyin 2" (salt tolerant cultivar) increased when the roots were exposed to 50-200 mmol/L NaCl for 2 d, and decreased when NaCl concentration was increased to 600 mmol/L. In “Kepin 7" (salt sensitive cultivar), tonoplast H+ ATPase activity in roots also increased at lower levels of NaCl (50-100 mmol/L), but decreased at higher levels of NaCl (200-600 mmol/L). Tonoplast fluidity in roots of“Tanyin 2" decreased at 50-200 mmol/L NaCl, and increased significantly at 600 mmol/L NaCl. Under salt stress, the change of tonoplast fluidity was identical with that of the ratio of unsaturated fatty acids to saturated fatty acids in tonoplast lipid of barley roots. It is proposed that the increase of tonoplast fluidity due to increased degree of unsaturation of fatty acids is one of the reasons leading to the decrease of H+ ATPase activity under higher level of NaCl stress.
NaCl
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