Effects Of NaCl And KCl Treatment On Salt Glands Development And Salt-secretion Rate Of The Leaves Of Limonium Sinense

The most remarkable morphological characteristics of recretohalophytes are the salt-secreting structures (salt glands and salt bladders) that can excrete excessive salts. They play an important role in regulating ion balance, maintaining the stability of osmotic pressure and enhancing the salinity tolerance. It is clear that the gland secretion increases with external concentration of exposure to salinity and the composition of the secretions is highly dependent on the composition of the root environment. However, there are three particularly pertinent questions that have not been satisfactorily resolved: one is that the variation of salt secretion rate is due to the efficiency of the secretion process per salt gland or to changes in the number of salt glands at different salinity levels? The second is that there is any selectivity in different ions per salt glands? The last is what's the relationship between the salt secretion rate and the development of salt glands? Limonium sinense seedlings were used to study the effects of NaCl and KCl on the growth, development and salt secretion rate of salt glands. The results were shown as follows:1 Effects of NaCl and KCl on growth of Limonium sinenseBoth the fresh and dry weight of the whole plant increased with increasing NaCl concentration. Both the fresh and dry weight of the whole plant reached the maximum under 100 mmol/L NaCl treatment and then declined with increasing NaCl concentration. Both the fresh and dry weight of the whole plant increased with increasing KCl concentration and reached the maximum under 50 mmol/L KCl treatment, and then declined with increasing KCl concentration.2 Effects of NaCl and KCl on development of salt glandsUnder 100 mmol/L and 200 mmol/L NaCl treatment, the average diameter of salt glands was significantly bigger than that of controls; No significant difference was observed between plants treated with 300 mmol/L NaCl and controls. Under 100 mmol/L KCl treatment, the average diameter of salt glands was significantly bigger than that of controls, while the average diameter of salt glands was significantly smaller than that of controls under 200 mmol/L and 300 mmol/L KCl treatments. There was no significant difference in the average diameter of salt glands between plants treated with 100 mmol/L NaCl and 100 mmol/L KCl. When the concentrations of NaCl and KCl were 200 mmol/L or 300 mmol/L, the diameters of salt glands under NaCl treatment were significantly bigger than those under KCl treatment. The total number of salt glands under NaCl and KCl treatments was significantly higher than that of controls.3 Effects of NaCl and KCl on salt secretion rate of salt glandsSalt secretion rate per salt gland and per leaf increased markedly with the increase of NaCl and KCl concentrations. When the concentrations of NaCl and KCl were 100 mmol/L or 200 mmol/L, Na+ secretion rate per leaf was significantly higher than K+ secretion rate. When the concentrations of NaCl and KCl were both 200 mmol/L, Na+ secretion rate per salt glands was significantly higher than K+ secretion rate. There was no significant difference between the Na+ secretion rate per salt glands and K+ secretion rate under 100 mmol/L and 300 mmol/L NaCl and KCl treatments.The results suggested that modest NaCl and KCl treatments significantly stimulated the development and salt secretion rate of salt glands of Limonium sinense, severe NaCl and KCl treatments inhibited the development of salt gland significantly, but still markedly enhanced salt secretion rate.