PHYSIOLOGICAL AND BIOCHEMICAL RESPONSES OF A MEDICINAL HALOPHYTE LIMONIUM BICOLOR (BAG.) KUNTZE TO SALT-STRESS

Limonium bicolor (Bag.) Kuntze is a perennial herb belonging to the Plumbaginaceae family. It is a typical recretohalophyte as well as a medicinal plant, distributing at saline soil areas in coastal areas and grasslands. In this paper, physiological mechanisms of L. bicolor to defend salt stress and effects of salinity on medicinal ingredients were investigated. The effects of different NaCl concentrations on the number of salt glands, Na+ content, dry weight and water content in tissues, gas exchange parameters involving net CO2 assimilation rate, stomata] conductance, intercellular CO2 concentration and transpiration rate, malondialdehyde content and electrolyte leakage, activities of superoxide dismutase, peroxidase and catalase and accumulations of secondary metabolites such as total phenolic, total flavonoid, gallic acid and myricetrin of leaves were determined. The results show that 100 and 200 mM NaCl induced facilitated effects in L. bicolor reflected in the increase in dry weight, tissue water content, net CO2 assimilation rate, the number of salt glands, activity of superoxide dismutase, and content of gallic acid and myricetrin. The 300 mM NaCl treatment resulted in obviously decline in gas exchange parameters, and significant increases in Na+ levels, malondialdehyde level and electrolyte leakage. It was suggested that increased salt tolerance of L. bicolor was due to the corresponding resistance mechanisms involving an increased number of salt glands; enhanced activities of antioxidant enzymes, and an accelerated accumulation of secondary metabolites. What's more, the results on effects of salinity on medicinal ingredients in L. bicolor under different salt concentrations could provide theoretical basis for the standardization cultivation technique of L. bicolor.