Effect of CO2 Concentration During Growth on a CO2 Concentrating Mechanism in White Clover as Predicted from Differential 14CO2/12CO2Uptake

Lehnherr, B. Mâchler, F. and Nosberger, J. 1985. Effect of C02 concentration during growth on a C02 concentrating mechanism in white clover as predicted from differential 14C02/12C02 uptake.— J. exp. Bot. 36: 1835-1841. White clover was grown at 20 and 100 Pa p(C02). The C02 response of net photosynthesis and differential uptake of 14CO, and 12C02 by leaves were measured at various temperatures and at various 02 and C02 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 C02 concentrating mechanism. Plants grown at 20 Pa p(C02) showed a higher affinity for C02 than plants grown at 100 Pa p(C02) when measured at 10 °C. No difference in affinity was found at 30 °C. The postulated C02 concentrating effect was greater in plants grown at low C02 than in plants grown at high C02 concentration and occurred only at low temperature and low C02 partial pressure. It is suggested that plants grown at the lower C02 partial pressure have a higher affinity for C02 due to a more efficient C02 concentrating system than plants grown at the higher C02 partial pressure.