With K326 varieties in flue-cured tobacco as the test materials,ammonia collection device and glutamine synthetase (GS) inhibitor (Glufosinate) handling leaves and the apoplast extraction method to study the relationships between ammonia volatilization and physiological parameters related with nitrogen metabolism.The results show that:(1)GS plays a leading role as the leaf senescence,the amount of ammonia volatilization in the age of 70 d is the largest (10.96 μg·m^-2·h^-1),increased of 2.15 times compared to that of aging initial (age 40 d);Apoplastic NH₄⁺ concentration and pH,ammonia compensation point gradually increased;GS and nitrate reductase (NR) activities decreased,glutamate dehydrogenase (GDH) activity increased;soluble protein and total nitrogen degradation,leaf NH₄⁺ concentration increased.(2) With GS inhibitor,leaf tissue concentrations of NH₄⁺ and ammonia compensation point increased,the amount of ammonia volatilization was increased significantly,compared with the control.(3)The amount of ammonia volatilization and apoplastic NH₄⁺ concentration,apoplastic pH and ammonia compensation point were significant or extremely significant and positively correlated;And the activity of GS was negative significantly correlated;And GDH activity was positively correlated with the concentration of NH₄⁺;and blade organization NH₄⁺ concentration and other index is not significantly related.In summary,flue-cured tobacco leaves during senescence of ammonia volatilization volume increased significantly.It is regulated directly with ammonia compensation point,GS and GDH activities,as well as adjusted indirectly with other nitrogen metabolism indexes,in which GS plays the leading role.