Abstract:

The activity of H⁺-ATPase，fatty acid composition and membrane fluidity of tonoplast vesicles isolated from roots and leaves of Broussonetia papyrifera plantlets under salt stress with different concentrations of NaCl were investigated. The results showed that V-H⁺-ATPase activity in roots increased at low level of NaCl concentration (50 mmol·L^-1). When NaCl concentration exceeds 100 mmol·L^-1，the activity was similar with control. In leaves，V-H⁺-ATPase activity decreased at 100 mmol·L^-1 NaCl，but increased at higher levels of NaCl (150 mmol·L^-1). It was found that the fatty acid composition of tonoplast was consisted of C16： 0，C16： 1，C18： 0，C18： 1，C18： 2 and C20： 0. Alterations in relative content of tonoplast fatty acid composition under NaCl stress were observed. In roots the extent of unsaturation of tonoplast fatty acids decreased, and then it increased under 150 mmol·L^-1 NaCl. In leaves，the extent of unsaturation of tonoplast fatty acids decreased under 50 mmol·L^-1 NaCl treatment，however the extent increaseal with the increase of salinity,leaves and was higher than that in control. The changes in tonoplast fluidity coincided with those in unsaturation of fatty acids under NaCl stress. Tonoplast fluidity decreased with the decline of unsaturation of fatty acids. The objectives of this study were to gain better understand of the adaptive mechanism of H⁺-ATPase，fatty acid composition and membrane fluidity of tonoplast of woody plants and their relationship under salt stress.

Key words: Broussonetia papyrifera, salt stress, tonoplast, fatty acid, membrane fluidity, H⁺-ATPase