Comparative Studies On Plasma Membrane Function Of Salt-secreting And Non-salt-secreting Mangrove Plant Seedlings

The salt-secreting mangrove, Avicennia marina, and non-salt-secreting mangrove, Kandelia candel were cultivated in sand with various salinities (0%o,10%o,20%o,30%o,40%o) for 60d. High-purity plasma membrane vesicles in leaves and roots of A.marina and K.candel seedlings were abtained by two-phase partitioning. The function of the plasma membranes, such as the activity of ATPase, redox system, membrane potential, transmembrane proton gradient, membrane lipid superoxidation and activity of superoxide dismutase (SOD) at various salinities were investigated. The results showed that:1 Within a certain range of salinity (A. marina and roots of K. candel : 0-30%o; leaves of K.candel : 0-20%o), the activity of ATPase and redox system increased with increasing substrate salinity. While high salinity (above 30%o or 20%o) inhibited their activities. In comparison with A.marina, K.candel appeared more sensitive to salinity.2 The dynamics of membrane potential and transmembrane proton gradient in leaves and roots of A.marina and K.candel seedlings were similar to that of ATPase and redox system.3 The concentration of MDA, product of lipid peroxidation, and the rate of CV generation declined within certain range of salinity, and increased at high salinity with turning points at 30%o (roots of K.candel and leaves of A.marina ) and 20%o (leaves of K.candel). For the roots of A.marina, the concentration of MDA still declined at 40%o. Theactivity of SOD in K.candel increased apparently below the salinity of 10%o (leaves) and 30%o (roots), then declined rapidly. As to A.marina, the activity of SOD also increased apparently with the changes of salinity in roots, but there was no obvious change in leaves. 4 All the enzymes mentioned above in the plasma membrane vesicles in leaves of A.marina and K.candel, which was treated directly by NaCl was inhibited obviously: there was a little increase within 0-10%o (K.candel) or 0-20%o (A.marina) foil- owed by quickly declining. And the accumulation of MDA was accelerated, which suggest that the structure and function of plasma membrane was damaged severely.