Uncertainties and limitations of using carbon‐13 and oxygen‐18 leaf isotope exchange to estimate the temperature response of mesophyll CO2 conductance in C3 plants

摘要: The internal CO2 gradient imposed by mesophyll conductance (gm ) reduces substrate availability for C3 photosynthesis. With several assumptions, estimates of gm can be made from coupled leaf gas exchange with isoflux analysis carbon ∆13 C-gm and oxygen in , transpired water (H2 O) ∆18 O-gm to partition into its biochemical anatomical components. However, these assumptions require validation under changing temperatures. To test we measured modeled the temperature response (15-40°C) along biochemistry grass Panicum bisulcatum, which has naturally low carbonic anhydrase activity. Our study suggests that regarding extent isotopic equilibrium (θ) between H2 O at site exchange, composition sites evaporation ( δw-e18 δw-ce18 are similar, may lead errors estimating response. input parameters appear less sensitive temperature. this needs tested species diverse Additional information on dependency cytosolic chloroplastic pH clarify uncertainties used