Elevated atmospheric CO2 decreases the ammonia compensation point of barley plants

Abstract

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.

Keywords

ammonia compensation point (NH3); barley; carbon dioxide (CO2); climate change; nitrate reductase; nitrogen metabolism

Published in

Journal of Experimental Botany
2013, volume: 64, number: 10, pages: 2713-2724

SLU Authors

• Eriksson, Dennis

  • University of Copenhagen

UKÄ Subject classification

Biochemistry
Molecular Biology

Publication identifier

• DOI: https://doi.org/10.1093/jxb/ert117

Permanent link to this page (URI)

https://res.slu.se/id/publ/79639