Stomatal NH3 compensation point and its metabolic regulation in senescence phenotypes of Nicotiana tabacum

Abstract

We compared stomatal ammonia compensation point (χs) and its metabolic regulation in tobacco (Nicotiana tabacum) leaves of a quick-leaf-senescence phenotype ZY90 and a slow-leaf-senescence phenotype NC89. Compared with NC89, ZY90 had significantly higher χs values between 40 and 60 d after leaf sprouting in spite of its lower nitrogen content. During the same time, a steeper decline in glutamine synthetase activity was detected in ZY90 leaves, simultaneously with a steep increase in χs. These results suggested that the quick leaf senescence phenotype exhibited high NH3 emission potential due to efficient nitrogen recycling and remobilization, and glutamine synthetase played a key role in regulating χs in ZY90.

Keywords

• glutamine synthetase
• nitrogen content
• quick- and slow-leaf-senescence phenotypes
• tobacco