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In the present work, an intensive tolerance to high salt stress of embryogenic suspension cultures from two reed (Phragmites communis Trin.) ecotypes, dune reed and swamp reed, was found and studied. The dune reed was more resistant than the swamp reed to salt. Aiming at better understanding the characteristic tolerance to salt stress in reed plants, changes of respiration and respiratory pathways in both reed suspension cultures exposed to 50-800 mM NaCl stress were measured and analyzed. The results demonstrated that the respiration rates of both reed cultures increase significantly during the 50-400 mM NaCl treatment. Inhibition tests with cyanide and salicylhydroxamic acid showed that the increasing respiration rate resulted from high operation of the cytochrome pathway in the dune reed, and cooperation of the cytochrome pathway and an alternative pathway in the swamp reed. The respiration rates of both reed cultures decreased dramatically following 800 mM NaCl treatment. The results were due to the low level of the cytochrome pathway. Notably, the operation of the alternative pathway in both reed cultures in the presence of 800 mM NaCl sustained a similar level of respiration to that in the absence of salt, indicating a high contribution of the alternative pathway to the total respiration. The alternative pathway is thought to be a response to severe stress in both reed suspension cultures, and it seems to be more important to stress tolerance in the swamp reed. [ABSTRACT FROM AUTHOR]