Wang, Liang3; Pedas, Pai3; Eriksson, Ulf Dennis3; Schjørring, Jan K.4
1 Section for Plant and Soil Sciences, Department of Plant and Environmental Sciences, Faculty of Science, Københavns Universitet2 Department of Agriculture & Ecology, Plant and Soil Science, Department of Agriculture & Ecology, Faculty of Life Sciences, Københavns Universitet3 Department of Agriculture & Ecology, Plant and Soil Science, Department of Agriculture & Ecology, Faculty of Life Sciences, Københavns Universitet4 Section for Plant and Soil Sciences, Department of Plant and Environmental Sciences, Faculty of Science, Københavns Universitet
The ammonia compensation point (chi(NH3)) controls the direction and magnitude of NH3 exchange between plant leaves and the atmosphere. Very limited information is currently available on how chi(NH3) responds to anticipated climate changes. Young barley plants were grown for 2 weeks at ambient (400 mu mol mol(-1)) or elevated (800 mu mol mol(-1)) CO2 concentration with NO3- or NH4NO3 as the nitrogen source. The concentrations of NH4+ 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 NH4+ concentration in the apoplastic solution and slightly acidified it. This resulted in a decline of the chi(NH3) 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 NO3- and NH4NO3 treatments, respectively. The decrease in chi(NH3) 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.
Journal of Experimental Botany, 2013, Vol 64, Issue 10, p. 2713-2724