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 (Ca and
Mg), 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.
Pattern of antioxidant enzyme activities and hydrogen peroxide content during developmental stages of rhizogenesis from hypocotyl explants of Mesembryanthemum crystallinum L.
