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Effect Of KCl Treatment On The Plasma Membrane H~+-ATPase Activity Of Suaeda Salsa.

Posted on:2006-07-11Degree:MasterType:Thesis
Country:ChinaCandidate:J R GuoFull Text:PDF
GTID:2120360155459786Subject:Botany
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Significant differences were observed in the effects of KCl stress and NaCl stresson plants. K+ is one of the three nutrition elements those are indispensable to plants. Itplays very important roles in growth and metabolism of plant cell, and it's the onlycation that is in high concentration existent in plant cells. Na+ is only a beneficialelement to some plants, Na+,K+ are all univalent elements, and they also have thesame atomic structure, but there were significant differences between the effects onplants. Plasma membrane is the first barrier between plant cells and the outerenvironment. Plasma membrane H+-ATPase (PM H+-ATPase) plays a key role inestablishment and maintenance of cellular ion homeostasis, it is considered as the'Master enzyme'in plants. The proton and electrical gradient across plasmamembrane produced by PM H+-ATPase is the driving force for solute uptake andactive secondary transport. And PM H+-ATPase may be primary responses toenvironmental stressors. In the present study, salt-dilution halophyte Suaeda salsacultured under different salts (100 mmol/L KCl and the same concentration NaCl) wasused to investigate the growth, water metabolism, ions, radical damage, activity andexpression of PM H+-ATPase of Suaeda salsa. The main aim is to search for thereasons for KCl toxicity. The main results are shown as follows.1. Effect of KCl and NaCl treatments on growth of Suaeda salsa seedlingsThe growth of S. salsa was enhanced by 100 mmol/L NaCl treatment, thebranching of shoots increased, seedlings and leaves were bigger than control. Thefresh weight of shoots increased significantly compared with control shoots (P<0.05).Compared with control, the seedlings of S. salsa were smaller under KCl (100mmol/L) treatment, the branches and leaves were small, young leaves curled, growingpoint etiolation, lignification degree increased (Fig.3), the fresh weight of shoots androots decreased.The growth of S. salsa was inhibited by KCl treatment, the water content, leafNa+ and Ca2+ contents decreased, while K+ content and roots/shoots increased. Innonhalophytes, K+ may be used as osmoticum to regulate the osmotic potential ofcytoplasm and vacuole, but in high K+ environment, S. salsa couldn't adapt to the lowwater potential. Under NaCl treatment the dry weight and water content increased,Na+ contents of leaves were significantly increased. It indicated that S. salsa can adapthigh NaCl environment and modulate the osmolarity by absorbing abundant Na+(Fig.3 5 7 8).2. Effect of KCl and NaCl treatments on the osmotic potential of cell sap of leaves of Suaeda salsa Seedling. In a saline environment, halophytes regulate osmotic potential mainly byaccumulating inorganic ions and small organic solutes to adapt osmotic stress. UnderNaCl treatment, the osmotic potential of the leaf cell sap of S. salsa was drasticallydecreased. S. salsa is a salt-dilution halophyte, it can alleviate salt toxicity throughextruding Na+ out of cell and sequestrating Na+ into the vacuole. The transportation ofNa+ against the concentration gradient from the cytoplasm into the apoplast and thevacuole via the plasma membrane Na+/H+ antiporter and the tonoplast Na+/H+antiporter, which are dependent on the activities of plasma membrane proton pump(PM H+-ATPase) and tonoplast proton pumps (V-H+-ATPase and V-H+-PPase). Whileunder KCl treatment, the osmotic potential of leaf cell sap of S. salsa seedlings wasnot drastically decreased, which suggested that no enough osmotic adjustmentoccurred in S. salsa seedlings exposed to KCl. The reasons are possible that S. salsacould not utilize K+ as osmoticum leading to water deficit and growth inhibition (Fig.15).3. The membrane damage of S. salsa leaves under KCl and NaCl treatments Lipid peroxidation (MDA) was used as indicators of salt stress to test the freeradical damage. Under KCl treatment, S. salsa leaf MDA content and the plasmalemmapermeabilty increased (Fig.17). That is to say that the membrane system of S. salsaleaves was damaged. While under conditions of NaCl, S. salsa leaf MDA contentdecreased and there are no distinct changes in the plasmalemma permeabilty. NaCltreatment stimulated the growth of S. salsa.4. Effect of KCl and NaCl treatments on the growth and proton excretion rate of S. salsa roots The growth of S. salsa roots was checked by root bending analysis, NaCltreatment stimulated the growth of S. salsa roots, and the length of roots weredrastically increased compared with control. While the root growth rate was slowunder KCl treatment.
Keywords/Search Tags:Suaeda salsa, growth, KCl treatment, PM H~+-ATPase
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