Concomitant accumulations of ions, osmoprotectants and antioxidant system-related substances provide salt tolerance capability to succulent extreme-halophyte Scorzonera hieraciifolia

Abstract

Halophytes adapting to live in salinized areas can activate some tolerance mechanism through signal compounds to cope with salinity. However, the role of co-activity of signal compounds in salt tolerance of halophytes is not yet fully understood. We have firstly detected that Scorzonera hieraciifolia with fleshy shoots is a succulent extreme-halophyte and researched the changes in signal compounds involved in the salt tolerance mechanism, including inorganic ions, osmoprotectants and substances related to antioxidant system. The levels of signal compounds such as calcium, magnesium, proline, soluble sugar, hydrogen peroxide, superoxide, ascorbate and glutathione concomitantly increased when thickness of shoot tissues enhanced under excess salinity. There were 3.3-fold, 5-fold, 8-fold and 10-fold enhancements in the levels of inorganic ions (Ca2+ and Mg2+), hydrogen peroxide, ascorbate and glutathione in the shoots treated with excess salinity, respectively. Contents of sodium, potassium and chlorine, and antioxidant enzyme activities, superoxide dismutase, guaiacol peroxidase, ascorbate peroxidase, catalase and glutathione reductase, also increased in the salinized shoots. Western blot analysis showed that the increases in antioxidant enzyme activities were consistent with increases in their protein contents. The results suggest that extraordinary salt tolerance capacity in Scorzonera hieraciifolia, a succulent extreme-halophyte can be improved by modulated accumulations of signal compounds, especially calcium, magnesium, osmoprotectants, reactive oxygen species and antioxidant substances. Moreover, massive induction of antioxidant enzymes can make strong contributions to salt stress tolerance of S. hieraciifolia.