Plant and Soil Science Section, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark.
J Exp Bot. 2013 Jul;64(10):2713-24. doi: 10.1093/jxb/ert117. Epub 2013 Jun 5.
The ammonia compensation point ( ) controls the direction and magnitude of NH3 exchange between plant leaves and the atmosphere. Very limited information is currently available on how responds to anticipated climate changes. Young barley plants were grown for 2 weeks at ambient (400 μmol mol(-1)) or elevated (800 μmol mol(-1)) CO2 concentration with or NH4NO3 as the nitrogen source. The concentrations of and H(+) in the leaf apoplastic solution were measured along with different foliar N pools and enzymes involved in N metabolism. Elevated CO2 caused a threefold decrease in the concentration in the apoplastic solution and slightly acidified it. This resulted in a decline of the from 2.25 and 2.95 nmol mol(-1) under ambient CO2 to 0.37 and 0.89 nmol mol(-1) at elevated CO2 in the and NH4NO3 treatments, respectively. The decrease in at elevated CO2 reflected a lower N concentration (-25%) in the shoot dry matter. The activity of nitrate reductase also declined (-45 to -60%), while that of glutamine synthetase was unaffected by elevated CO2. It is concluded that elevated CO2 increases the likelihood of plants being a sink for atmospheric NH3 and reduces episodes of NH3 emission from plants.
氨补偿点（ ）控制着植物叶片与大气之间 NH3 交换的方向和幅度。目前，关于如何应对预期气候变化的信息非常有限。将幼大麦植株在环境（400 μmol mol(-1))或升高（800 μmol mol(-1)) CO2 浓度下生长 2 周，以 NH4NO3 作为氮源。同时测量叶片质外体溶液中的浓度和 H(+)以及不同的叶片氮库和参与氮代谢的酶。升高的 CO2 使质外体溶液中的浓度降低了三倍，并使其略微酸化。这导致在环境 CO2 下，和 NH4NO3 处理的分别从 2.25 和 2.95 nmol mol(-1)下降到 0.37 和 0.89 nmol mol(-1)。在升高的 CO2 下减少，反映了地上部分干物质中氮浓度降低（-25%）。硝酸还原酶的活性也下降（-45 至-60%），而谷氨酸合酶的活性不受 CO2 升高的影响。结论是，升高的 CO2 增加了植物成为大气 NH3 汇的可能性，并减少了植物排放 NH3 的事件。
