Studies in the Nitrogen Metabolism of Apple Fruits: THE CLIMACTERIC RISE IN RESPIRATION IN RELATION TO CHANGES IN THE EQUILIBRIUM BETWEEN PROTEIN SYNTHESIS AND BREAKDOWN

1. A close parallelism in the drift of the rate of respirationand the protein-N/ non-protein-N ratio is shown to occur bothin apple fruits attached to the tree and when detached fromthe tree at various stages of development and stored for severalmonths at 12 C.
2. In detached fruits the fall in respirationwhich occurs immediately(during the first 48 hours) after pickingis only accompaniedby a concomitant fall in net protein invery young fruits inwhich active cell division is taking place.Subsequently, infruit of all ages when a climacteric rise inrespiration occursit is accompanied by a net increase in protein.
3. It is argued that the climacteric rise in respiration is aresultof increase in the level of protein which will be expectedtoreduce the ATP/ADP ratio.
4. Over the climacteric period,although rate of respiration andnet protein content both rise,R rises more rapidly than proteinand, subsequently, falls ata faster rate than P. It is suggestedthat this may be due tothe ‘new’ protein containinga higher proportionof enzyme(s) directly involved in respirationand leading, forexample, to a reduction in the ATP/ADP ratio.