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 has not yet fully understood. We researched the changes in signal compounds involved in the salt tolerance mechanism, including inorganic ions, osmoprotectants and substances related to the antioxidant system in Scorzonera hieraciifolia with fleshy shoots extreme-halophyte. The levels of calcium, magnesium, proline, soluble sugar, hydrogen peroxide, superoxide, ascorbate and glutathione 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+), H2 O2, ascorbate and glutathione in the shoots treated with excess salinity, respectively. Contents of sodium, potassium and chlorine, and antioxidant enzyme activities also increased in the salinized shoots. The increases in antioxidant enzyme activities were consistent with increases in their protein contents according to Western blot analysis. The results suggest that extraordinary salt tolerance capacity in Scorzonera hieraciifolia can improve by modulated accumulations of signal compounds, particularly calcium, magnesium, osmoprotectants, reactive oxygen species and antioxidant substances. Moreover, massive induction of antioxidant enzymes can make strong contributions to salinity tolerance of S. hieraciifolia.