Carbon dioxide fixation in the nodules of amide transporting vs ureide transporting legumes

The ability of nodules of amide transporting legumes, clusterbean (Cyamopsis tetragonoloba L.) and groundnut (Arachis bypogaea L.) to fix carbon dioxide was compared with that of ureide transporting legume, mungbean (Vigna radiata L. Wilczek.) by assaying the activity of the enzyme phosphoenol pyruvate carboxylase in vitro and by direct feeding of 14CO2. The activity of the enzyme was found to be several fold higher in amide transporters compared to ureide transporter. Similarly, 14CO2 incorporation was also higher, though only marginally in groundnut, in amide transporters than in the ureid transporter. Thus, any advantage in carbon usage in ureide transporter seems to be compensated by dark CO2 fixation in amide transporters. (author). 14 refs., 2 tabs