Strategies for adaptation of Suaeda physophora, Haloxylon ammodendron and Haloxylon persicum to a saline environment during seed-germination stage.
OBJECTIVE
Germination is very important for plant establishment in arid regions. The strategies taken by halophytes during the seed germination stage to adapt to saline environments in an arid zone were investigated in Suaeda physophora (euhalophyte), Haloxylon ammodendron (xero-halophyte) and Haloxylon persicum (xerophyte).


METHODS
Seeds of S. physophora, H. ammodendron and H. persicum were exposed to a range of iso-osmotic NaCl and PEG solutions. Seed germination in, and recovery germination from, high NaCl were recorded. The effects of iso-osmotic NaCl and PEG on seed water uptake and changes in ion content were measured. In addition, the structure of seeds and Na+ distribution in the seed coat and embryos of dry seeds were investigated.


RESULTS
The relative increase in fresh weight of germinating seeds was markedly reduced in -2.24 MPa PEG compared with that in -2.24 MPa NaCl, while the opposite trend was found in concentration of K+ during the initial 9 h for all species. Haloxylon ammodendron and S. physophora had a higher recovery germination from -3.13 MPa NaCl compared with H. persicum. Seeds of all species had no endosperm. More Na+ was compartmentalized in the seed coats of the two halophytic species compared with that in the xerophyte H. persicum.


CONCLUSIONS
The effect of NaCl on seed germination was due to both osmotic stress and ion toxicity for the three species. High soil salinity and a high content of Na+ in seeds may induce more seeds to remain ungerminated in S. physophora and H. ammodendron. Morphological structure and adaptation to salinity during seed germination may determine the geographical distribution of H. ammodendron and S. physophora in certain saline regions.
College of Resource and Environmental Science, China Agricultural University, Beijing 100094, PR China.
Jie
J
Song
Gu
G
Feng
Changyan
C
Tian
Fusuo
F
Zhang
D000222:Adaptation, Physiological; D027703:Amaranthaceae / Q000502:physiology*; D019663:Chenopodiaceae / Q000502:physiology*; D018525:Germination / Q000502:physiology*; D009997:Osmotic Pressure; D011092:Polyethylene Glycols / Q000494:pharmacology; D012639:Seeds / Q000254:growth & development*; D012965:Sodium Chloride / Q000737:chemistry / Q000378:metabolism; D013997:Time Factors; D014867:Water / Q000378:metabolism
D014867:Water; D011092:Polyethylene Glycols; D012965:Sodium Chloride