TY - JOUR
T1 - Light and CO2 do not affect the mesophyll conductance to CO 2 diffusion in wheat leaves
AU - Tazoe, Youshi
AU - Von Caemmerer, Susanne
AU - Badger, Murray R.
AU - Evans, John R.
N1 - Funding Information:
We thank Stephanie McCaffery for cultivating the wheat used in this study and Dr Asaph B Cousins for his technical help with the measurement of carbon isotope discrimination. This work was funded by ARC Discovery grant DP0771413.
PY - 2009/5
Y1 - 2009/5
N2 - In C3 plants, diffusion of CO2 into leaves is restricted by stomata and subsequently by the intercellular airspaces and liquid phase into chloroplasts. While considerable information exists on the effect of environmental conditions on stomatal conductance (gs), little is known on whether the mesophyll conductance to CO2 diffusion (gm) changes with respect to photon flux density (PFD) and CO2 partial pressure (pCO2). In this study, the effects of PFD and/or pCO2 on gm were examined in wheat leaves by combining gas exchange with carbon isotope discrimination measurements using a membrane inlet mass spectrometer. Measurements were made in 2% O2 to reduce the fractionation associated with photorespiration. The magnitude of gm was estimated using the observed carbon isotope discrimination (Δ), ambient and intercellular pCO2, CO2 assimilation and respiration rates, either from an individual measurement made under one environmental condition or from a global fit to multiple measurements where PFD was varied. It was found that respiration made a significant and variable contribution to the observed discrimination, which associated with the difference in isotopic composition between CO2 in the greenhouse and that used for gas exchange measurements. In wheat, gm was independent of PFD between 200 and 1500 μmol m-2 s-1 and was independent of pi between 80 and 500 μbar.
AB - In C3 plants, diffusion of CO2 into leaves is restricted by stomata and subsequently by the intercellular airspaces and liquid phase into chloroplasts. While considerable information exists on the effect of environmental conditions on stomatal conductance (gs), little is known on whether the mesophyll conductance to CO2 diffusion (gm) changes with respect to photon flux density (PFD) and CO2 partial pressure (pCO2). In this study, the effects of PFD and/or pCO2 on gm were examined in wheat leaves by combining gas exchange with carbon isotope discrimination measurements using a membrane inlet mass spectrometer. Measurements were made in 2% O2 to reduce the fractionation associated with photorespiration. The magnitude of gm was estimated using the observed carbon isotope discrimination (Δ), ambient and intercellular pCO2, CO2 assimilation and respiration rates, either from an individual measurement made under one environmental condition or from a global fit to multiple measurements where PFD was varied. It was found that respiration made a significant and variable contribution to the observed discrimination, which associated with the difference in isotopic composition between CO2 in the greenhouse and that used for gas exchange measurements. In wheat, gm was independent of PFD between 200 and 1500 μmol m-2 s-1 and was independent of pi between 80 and 500 μbar.
KW - Carbon isotope discrimination
KW - Cooporin
KW - Internal conductance
KW - Respiration
UR - http://www.scopus.com/inward/record.url?scp=65249101845&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=65249101845&partnerID=8YFLogxK
U2 - 10.1093/jxb/erp035
DO - 10.1093/jxb/erp035
M3 - Article
C2 - 19255060
AN - SCOPUS:65249101845
VL - 60
SP - 2291
EP - 2301
JO - Journal of Experimental Botany
JF - Journal of Experimental Botany
SN - 0022-0957
IS - 8
ER -