Respiratory Metabolism in Detached Rhododendron Leaves

Some of the measurements described below were first made many years ago (21; see 26, 27, 28) as part of an investigation of the occurrence of the Pasteur effect in plant organs. More recently, with the development of interest in factors controlling respiratory metabolism, our attention was redirected to 2 of the plant materials originally studied, namely rhododendron leaves for which there was evidence of a marked Pasteur effect and young seedlings of buckwheat, the one material used for which no evidence of a Pasteur effect emerged. This paper describes 1 part of this work and is restricted to restilts obtained with detached whole leaves of rhododendron. Many investigations made for convenience with leaf discs or slices will be described elsewhere later, for their relevance to metabolism in the intact leaf is still in some doubt. The experiments described here are largely concerned with production and consumption of metabolites in the leaves in air, in pure nitrogen, and on return to air after a period in nitrogen. Particular attention has been directed toward transitory changes in concentrations of glycolytic intermediates and keto-acids as guides to changes of rates of glycolysis and of oxidative reactions of the tricarboxylic acid cycle. These data have the limitation of all such measurements in that they represent average concentrations for whole cells which may bear little relation to changes in specific metabolic pools associated with glycolysis and cycle oxidations but are nevertheless a necessary preliminary to further work. Also, because of renewed interest elsewhere in the origin of the anaerobic CO, output (24) and of the possible consumption of ethanol (9, 10, 29), some attention is given here to these aspects of metabolism.