Comparative Study On Salt Tolerance Of Suaeda Salsa From Different Habitats During Germination And Seedling Stages

In this paper, the response of S. salsa from saline inland and intertidal zone to salt stress was investigated to elucidate the eco-physiological mechanism of adaptation of S. salsa from different habitats to saline environments. The result showed that:Seed germination stage: S. salsa produces dimorphic seeds, i.e. brown seeds with a soft outer seed coat and hard black seeds with a smooth outer seed coat. Total ion contents in brown seeds were higher than those in black seeds in both populations. These characteristics may be one of the reasons why brown seeds absorbed water more quickly than black seeds, and brown seeds had higher salt tolerance than black seeds in both populations. In addition, contents of total ions in brown seeds were higher, while those in black seeds were lower in S. salsa from the intertidal zone than those from inland population, which may be the reason why the rate of water uptake and salt tolerance of brown seeds were higher, while those of black seeds were lower in S. salsa from the intertidal zone than those in the inland population. High salinity (400 mM NaCl) had no inhibitory effect on seedling elongation from brown seeds, but seedling elongation from black seeds markedly decreased in 400 mM NaCl in both S. salsa populations. In conclusion, S. salsa has high salt tolerance during seed germination. High contents of ions in brown seeds may benefit them to absorb water and to germinate more rapidly than black seeds of both S. salsa populations in saline environments. The specie may establish its population mainly from brown seeds, especially for S. salsa from the intertidal zone.Seedling stage: salinity decreased the number of side branches along main stem, organic dry weight of shoots, chlorophyll content, photosynthetic oxygen evolution rate more severely in S. salsa from intertidal zone than those in the saline inland population. Chlorophyll a/b in leaves was higher in the intertidal population than that in the inland population. The Na+ and Cl- content (especially for Cl-) in leaves of S. salsa from the intertidal zone was lower than that in the saline inland habitats, while the opposite trend was true in the roots. Roots of S. salsa from the intertidal zone have a higher ability of ion exclusion (Na+ and Cl-) than that in the saline inland habitats. More Na+ and Cl- distributed in the cortex and vascular of roots in S. salsa from the intertidal zone than that in the inland habitats, which may be the reason why content of these ions in shoots of S. salsa from intertidal zone is lower than that in the saline inland habitats. In conclusion, S. salsa from intertidal zone may resist oxidative stress by maintaining their thylakoid stacking degree. Roots of S. salsa from intertidal zone may have a higher ability in salt exclusion and regulation of ion uptake or transport. The mechanism needs to be further studied.Photoperiodism study: the result showed that S. salsa is a short-day plant, the critical day length is 13 h/d in both populations. Time of inflorescences formation and flowering is earlier in S. salsa from saline inland than that in the intertidal population.