(15)N and Inhibitor Studies on the Photorespiratory Nitrogen Cycle in Maize Leaves

A combination of inhibitor and (15)N studies were used to investigate the photorespiratory nitrogen cycle in maize, a C4 plant. Inhibitors used included isonicotinyl hydrazide which blocks the conversion of glycine to serine, methionine sulfoximine an inhibitor of GS and azaserine an inhibitor of GOGAT. Results from levels of ammonia and amino acids and the distribution of (15)N into NH3, serine, glutamine and glutamate indicated that the photorespiratory N-cycle occurs in this C4 plant, but the rate of flux through this pathway is low as compared with that in C3 plants.