Abstract: Studies on the response of respiratory enzyme activities of halophyte Suaeda salsa seedlings growing under normal (350μl·L^-1) and doubled (700μl·L^-1) concentrations of CO₂ to KCl and NaCl show that under normal and doubled concentrations of CO₂, the activities of succinic dehydrogenase(SDH), malic dehydrogenase (MDH), Cytocrome Coxidase (CO), glycolate oxidase (GO) and hydroxypyruvate reductase (HPR) were inhibited by 300mmol·L^-1 KCl and NaCl;the activity of isocitric dehydrogenase (IDH) was decreased by NaCl, but increased by KCl.The operation rate of tricarboxylic acid cycle (TCAC) was deceleratedby CO₂ under KCl stress, but accelerated under NaCl salinity.The steps of limiting speed by TCAC's operation was not related with MDH.COis the important site of salt affecting respiratory metabolism.Moreover, the influence of K⁺ on protein expression was different from that of Na⁺, and CO₂ could reduce the protein expression of Suaeda salsa seedlings under NaCl and KCl stresses.

Key words: Suaeda salsa, KCl, NaCl, Doubled CO₂, Respiratory enzyme