AOBPreview originally published online on July 7, 2005
Annals of Botany 2005 96(3):399-405; doi:10.1093/aob/mci196
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Strategies for Adaptation of Suaeda physophora, Haloxylon ammodendron and Haloxylon persicum to a Saline Environment During Seed-Germination Stage
1 College of Resource and Environmental Science, China Agricultural University, Beijing 100094, PR China, 2 Institute of Ecology and Geography, Xinjiang, Academia Sinica, Urumqi 830000, PR China and 3 College of Life Science, Shandong Normal University, Jinan 250014, PR China
* For correspondence. E-mail fenggu{at}cau.edu.cn
Received: 18 March 2005 Returned for revision: 15 April 2005 Accepted: 11 May 2005 Published electronically: 7 July 2005
• Background and Aims 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.
• Key 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.
Key words: Adaptation, embryo, germination, halophyte, Haloxylon ammodendron, Haloxylon persicum, ion compartmentalization, ion toxicity, osmotic stress, seed coat, Suaeda physophora, xerophyte
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