Characteristic And Mechanism Of Osmotic Adjustment In Limonium Bicolor

The seedlings of Limonium bicolor were cultured in Hoagland solution with different salinities-0,100,200 and 400mmol/L NaCl respectively. The paper is mainly concerned with three aspects in the osmotic adjustment mechanism of the Limonium bicolor namely study on inorganic and organic substances contents and their contribution to osmotic adjustment; study on relation between osmotic adjustment and photosynthesis and study on inorganic ions distributing in leaf cells.1. Effects of NaCl treatments on growth of Limonium bicolorSeedlings of Limonium bicolor grow best and both the fresh and the dry weights in above-ground part reach the maximum under the condition of lOOmmol/L NaCl. Either the fresh or the dry weight of the above-ground part decreases gradually with the increasing of NaCl concentration. The water content in above-ground part increases and then decreases while that in below-ground part decreases and then increases with the increasing of NaCl concentration. And the root/shoot ratios of fresh and dry weight decrease and then increase with the increasing of NaCl concentration.2. Effects of NaCl treatments on contents of inorganic or organic substances in Limonium bicolorNa+ and Cl" contents increase sharply with the increasing of NaCl concentration. Under the condition of 400mmol/L NaCl. Na" and Cl" contents in above-ground part are 6.13 and 5.24 times of control respectively. And those in below-ground part are 14.0 and 13.8 times of control respectively. While the contents of K+. Ca2+. Mg2+. NOs" are all decrease gradually with the increasing of NaCl concentration.Both the content of free amino acid and that of proline increase. With the same concentration of NaCl treatment, the content of proline in below-ground part is higher than that in above-ground part significantly. The contents of organic acid in above-ground part or in root are both decrease gradually, while the decreasing speed in shoot is faster than that in root. The content of soluble sugar in above-ground increases and then decreases, and that in root increases continuously with the increasing of NaCl concentration.3. Contribution of organic or inorganic substances to osmotic adjustment under treatments of NaClContribution of inorganic ions to osmotic adjustment is much more excessive than that of organic substance and percentage of organic osmotica to the calculated osmotic potential is not over 10% in above-ground part. Contribution of organic osmotica in root is much bigger than that in above-ground part, but it is still rare compared to contribution of inornic ions. Anyhow, inorganic ions are the dominating osmotica in Limonium bicolor.4. Relation between osmotic adjustment and photosynthesisContent of chlorophyll a in leaves increases, while that of chlorophyll bdecreases and then increases with the increasing of NaCl concentration and it reaches the minimum under condition of lOOmmol/LNaC). The total contents of chlorophyll a and b increase, and chlorophyll a/b increase and then decrease with the increasing of NaCl concentration.The net photosynthetic rate of leaves increases and then decreases with the increasing of NaCl concentration. The decreasing extent of stomatal conductance in leaves is harder than that of net photosynthetic rate, which indicates that osmotic adjustment abates the inhibition on net photosynthetic rate caused by decreasing of stomatal conductance. 5. Distributing of dominant inorganic ions in leaf cellsThe relative contents of Na and Cl" in varied cells of salt gland are higher than those of epidermal cells and mesophyll cells significantly. Especially the relative contents of Na and Cl" in collect cells, secret cells are much high. And the contents of the two inorganic ions are least in mesophyll cells. Results also show that the Na and Cl" relative contents in vacuoles are higher than those in cytoplasm, indicating that the ions are mainly compartmented into vacuoles.