ANAEROBIC GERMINATION AND METABOLISM OF ERYTHRINA SEEDS WITH SPECIAL REFERENCE TO MITOCHONDRIA AND NITRATE REDUCTASE

Seeds of Erythrina caffra Thunb. are able to germinate anaerobically. Cycloheximide, chloramphenicol and malonate depressed germination. N-2 -incubated seeds metabolised [2-C-14] Na-acetate. Synthesis of ATP in embryonic axes of N-2-incubated seeds occurred to the same extent as i n air-germinated seeds. Cycloheximide but not chloramphenicol depresse d ATP and ethanol contents and respiratory capacity of embryonic axes. Embryonic axis mitochondrial O-2 uptake capacity was similar for seed s incubated for 24 h in air and N-2. The activities of five mitochondr ial enzymes at this stage were slightly lower in N-2-incubated than in air-incubated axes. However, at 12 h, i.e. prior to germination, acti vities in N-2-incubated axes were higher for malate dehydrogenase, oxo glutarate dehydrogenase and pyruvate dehydrogenase, similar for succin ate dehydrogenase and slightly lower for cytochrome oxidase than corre sponding activities in axes of air-germinated seeds. Mitochondrial pro tein synthesis occurred in axes of N-2-incubated seeds but at a slight ly lower rate than in air-incubated seeds. When assayed anaerobically nitrate reductase activity was found associated with purified mitochon dria. The nitrate reductase associated with mitochondria utilised NADH , succinate and to a lesser extent malate as electron donors. The acti vities measured were much lower than those of typical mitochondrial en zymes. It is concluded that mitochondrial activity occurs anaerobicall y in E. caffra embryonic seed axes and might possibly play a role in a noxic germination.