The Control of Anaerobic Respiration as a Determining Factor in the Distribution of the Genus Senecio

Abstract

Seven species of the genus Senecio, including 2 races of Senecio vulgaris, were grown in controlled conditions of high and low water tables in the glasshouse. All the species orginating from dry habitats were found to be restricted in their growth by the high water table conditions. A comparison of the rates of aerobic respiration of the excised roots showed no correlation between oxygen demand and the ability to grow in flooded conditions. A correlation was found, however, between growth and anaerobic respiration. All the plants that had their growth impeded by flooding were found to develop an increased rate of glycolysis on being kept in the high water table conditions for 1 mo. This was not the case with the plants from wet areas, where the rate of glycolysis, as measured both by carbon dioxide evolution and ethanol production, did not increase after the plants had been kept in flooded conditions. This inability to avoid an excessive rate of glycolysis with the possible accumulation of a toxic product may be the cause of the exclusion of these plants of dry habitats from wet areas.