Analytic studies in plant respiration. IV.—The relation of the respiration of potatoes to the concentration of sugars and to the accumulation of a depressant at low temperatures. Part I.—The effect of temperature-history on the respiration/sugar relation

Abstract

Analysis of the relation between the respiration of potatoes and the sugar content, the latter being varied by exposure of the material at different temps., revealed a new type of temp. effect, which consisted in the enduring depression of respiration by exposure to low temp. This effect persists for several weeks after the material is returned to a higher temp. The depression of the respiratory mechanism is attributed to the combined action of 2 separate processes: the accumulation of an inhibitor and the development of its effect. Both these processes are strongly affected by temp., but in opposed directions. The marked influence of the previous and current temps. on the grade of depression resulted in a whole series of respiration/sugar curves of widely varying form and pitch. The form of the highest and presumably normal respiration/sugar curve for[long dash]1[degree]C. was compared with the enzymatic rectangular hyperbola for an enzyme reaction in vitro and found to be closely though not completely conformable with the enzymatic curve. By comparing the form of the highest or undepressed respiration/sugar curves with the lowest or fully depressed curves, the inhibitor was shown to have the characteristics of a competitive inhibitor in an enzyme reaction in vitro. A method was put forward of evaluating the relative amounts of the inhibitor.