烟叶氨气补偿点的品种间差异及其与氮素代谢的关系研究

为了研究不同成熟特性的烤烟品种叶片氨气补偿点及其差异，利用质外体提取方法对3个烤烟品种NC89、K326和中烟90的叶片质外体铵浓度和pH值进行了测定，并计算不同品种叶片的氨气补偿点(25℃)；同时探讨了氨气补偿点与氮素代谢的关系。结果表明，叶片氨气补偿点随着成熟衰老而上升；烟草叶片成熟衰老期氨气补偿点与谷氨酰胺合成酶活性关系密切。衰老速度快、叶片氮素状况（总氮和可溶性蛋白）低的品种谷氨酰胺合成酶活性下降幅度大，氨气补偿点升幅大，绝对值也高。因此，衰老速度快、叶片氮素状况低的品种在叶片衰老期具有更大的氨挥发潜力。品种间氨气补偿点的差异与它们的氮素代谢特性有关。

Differences in NH3 compensation point among tobacco (Nicotiana Tabacum L.) cultivars and its relationship with nitrogen metabolism

To investigate NH3 compensation point (s) and its differences in leaves of three flue-cured tobacco genotypes and the related N metabolization, foliar apoplastic NH4+ concentration and pH were measured by apoplast extraction technique, the s (25℃) was calculated on the basis of measurements, and the activities of related enzymes and nitrogen parameters were also assayed. In the leaves of the three cultivars, an increase in s was observed as the onset of senescence. Compared with the leaves of slow-senescing cultivar, the leaves of the rapid-senescing tobacco cultivar with lower N status had a stronger decrease in glutamine synthetase activity (GS, EC 6.3.1.2) and a more substantial increase in s. These results indicate that the rapid-senescing cultivar may have a high potential for NH3 emission from senescing leaves into the atmosphere, and the difference in s values is related with the N metabolism of the cultivars.