Effect of CO₂Concentration During Growth on a CO₂Concentrating Mechanism in White Clover as Predicted from Differential¹⁴CO₂/¹²CO₂Uptake

Abstract

Lehnherr, B. Mächler, F. and Nösberger, J. 1985. Effect of CO2 concentration during growth on a CO2 concentrating mechanism in white clover as predicted from differential 14CO2/12CO2 uptake.- J. exp. Bot. 36: 1835-1841. White clover was grown at 20 and 100 Pa p(CO2). The CO2 response of net photosynthesis and differential uptake of 14CO2 and 12CO2 by leaves were measured at various temperatures and at various O2 and CO2 partial pressures and compared with predictions from ribulose bisphosphate carboxylase/oxygenase kinetics. Discrepancies between the observed gas exchange characteristics for the leaves and those predicted from the enzyme kinetics were interpreted as being due to a CO2 concentrating mechanism. Plants grown at 20 Pa p(CO2) showed a higher affinity for CO2 than plants grown at 100 Pa p(CO2) when measured at 10 °C. No difference in affinity was found at 30 °C. The postulated CO2 concentrating effect was greater in plants grown at low CO2 than in plants grown at high CO2 concentration and occurred only at low temperature and low CO2 partial pressure. It is suggested that plants grown at the lower CO2 partial pressure have a higher affinity for CO2 due to a more efficient CO2 concentrating system than plants grown at the higher CO2 partial pressure.