Adaptation Of Suaeda Salsa To Saline Environments During Seed Development

Responses of Suaeda salsa from saline inland or intertidal zone to saline environmentsduring seed development in field or controlled conditions were investigated in this study.Therefore, this study will present some information, which will help us to understand theeco-physiological mechanism of adaptation of halophytes to saline environments during seeddevelopment.Firstly, the importance of ion and chlorophyll accumulation in brown seeds during seeddevelopment for S. salsa in an intertidal zone and on saline inland was evaluated. The resultsshowed that more NO₃^-and K⁺, but less Cl^-and Na⁺in leaves and stems were translocated tothe embryos in the intertidal population than the inland population; more Cl^-and Na⁺werecompartmentalized in the pericarps of the intertidal population compared to the inlandpopulation, which indicates that S. salsa in an intertidal zone and on saline inland has differentability to accumulate ions in different plant parts. The embryos of fresh premature seedscontained chlorophyll and could release oxygen. The content of chlorophyll markedlydecreased, and there was no oxygen production in the embryos of dry mature seeds in bothpopulations. These characteristics may affect the distributions of the two S. salsa populationsin their natural saline environments.Secondly, the relationship between ion distribution in developing seeds of two Suaedapopulations and seed germination and seedling emergence was investigate in controlledconditions. Seeds were harvested from S. salsa plants that had been treated with1or400mMNaCl for122(inland population) or135days (intertidal population) in a glasshouse.Germination and seedling emergence were evaluated under salinity. In both populations, moreions were accumulated in the pericarps of plants cultured in400mM NaCl than in1mM NaCl.Pericarps accumulated much higher ion concentrations in the intertidal zone population than inthe saline inland population, while the opposite trend occurred for ion accumulation in theembryos. Seeds of plants from the intertidal population germinated more rapidly than thosefrom plants of the inland population, regardless of the NaCl concentration during seedgermination. However, seedling emergence under high salinity was lower with seeds from theintertidal population than with seeds from the inland population. In conclusion, S. salsa in the intertidal zone employs superior control of ion compartmentalization in the pericarps totolerate salinity but requires a minimal level of ions in embryos to ensure seedlingestablishment in highly saline environments. This indicates that euhalophytes require saltsduring the mature seed stage to maintain seed viability and to ensure seedling emergence andpopulation establishment.Thirdly, the relationship between organic solute and ions accumulation in developing seedsand seed germination and seedling emergence was investigate in controlled conditions. Seedswere harvested from plants of the inland population that had been treated with1or500mMNaCl for122days. The contents of amino acids, Na⁺and chlorophyll and the oxygenevolution were higher in the embryos of plants cultured in500mM NaCl than in1mM NaCl.The relative conductivity in high salinity was lower in the embryos of plants cultured in500mM NaCl than in1mM NaCl. Seed germination, germination rate, seedling emergence,survival seedings of seeds from the plants cultured in500mM NaCl was higher than in1mMNaCl under high salinity. This indicates that euhalophyte S. salsa requires salts during seeddevelopment stage to maintain the integrality of plasma membrane of seeds to maintain seedviability, which may help seeds to germinate and emerge successfully under high salinity.