Limonium Leaf Salt Gland Function And Mechanism Of Salt Excretion In The Discussion

The plants are respectively treated with 100 mmol/L NaCl. NaBr. NaIand the contents of Na+ secreted by the leaves are respectively determined.The TesuIts suggest that Br- inhibits the pIants to secret Na+, whi1e Cl-promotes the plants to secret Na+. The plants are respectively treatcd withl 00 mmol/L NaC1. NaHCO3. Na2SO4 and the contents of Na+ secreted by theleaves are respectively determined. The results suggest that both SO#'- andHCO3- inhibit the p1ants to secrete Na+, while Cl- promotes the p1ants tosecrete Na+. The plants are respectively treated with 100mmol/L NaCl \ KCl.CaCl2. MgC12 and the contents of cations secrcted by the leaves arerespectively determined. The results suggest the content of Ca2+ secreted bythe leaves is the highest.The ATPase activity of sa1t gland cel1s is studied by Pb3(PO4)2 deposition.The result is the plasma membrane ATPase activity in the collecting cells andouter cup celIs of saIt gIand treated with saIt is higher whiIe the salt gIandcells of the control almost have no ATPase activity. This suggests that in thecourse of secreting salt the ions come into the col1ecting cells actively bymeans of the plasma membrane H+--ATPase and after the ions come into thetransfusion zone, they come into the inner salt gland cells actively by meansof the plasma membrane H+-- ATPase of the outer cup ce1ls. The tonoplasts ineach cell of salt gland treated with salt have faint ATPase activity. lt suggestsit may be an inactive course that the ions come into the vacuoles.The ions contents in each salt gland cell are rneasured by X-raymicroanalysis. The contents of Na+ and Cl- in the small vacuoles of each saltgland cel1 are higher than those in the cytop1ast. 1t suggests that the smallvacuoles pIan an important role in the course of secreting. The contents ofNa+ in the vacuoles of secreting cells is higher than those ill the vacuo1es ofadjoining cells\ inner cup cells. outer cup ce1ls and the contents of Cl- are alsohigher. Jt suggests that secreting is not a continuous course but a periodicalactivity. In the secreting cells, the ion contents in the vacuo1es and cytoplastare higher. It suggests the cytoplast in the secreting cells has a strong abi1ityto adapt sa1t. The contents of Na+ and Cl* in the vacuoles of the collectingcells are higher. The co1lecting cells may col1ect ions by p1asma membrane H+--ATPase and then transport them into the inner salt gland cells. The ioncontents in the vacuo1es and cytoplast of the epidermal cells andmesophyllous cells are Iower than those in the salt gland ce1ls. It suggests thatLimonium can effective1y decrease the salt contents in the plant by salt glandsto maintain norma1 physiologicaI function. The contents of K+ in eacl1 cel1s ofLimonium treated with salt decrease because of the ion balance.