Carbohydrates in Leafy Spurge Roots as Influenced by Environment

Abstract

The total nonstructural carbohydrate (TNC) content of leafy spurge (Euphorbia esula L.) roots was determined for 4 consecutive growing seasons. The variations in water soluble (monosac-charide and disaccharide) and water insoluble or reserve carbohydrate content were compared to selected environmental parameters. TNC concentration reached maximum levels of 300 mg/g in mid-summer and early fall, but declined rapidly to 190 mg/g or less late in the growing season. The soluble carbohydrates, mostly sucrose, increased as the plant cold-hardened, while the insoluble carbohydrate content declined to near zero. Abrupt changes of root carbohydrate content could not be explained solely by the growth pattern of leafy spurge. Soluble carbohydrate content was high during periods favorable for growth, but insoluble reserves increased during periods of environmental stress. Root soluble carbohydrate content varied inversely with changes in the six day mean air temperature with an average partial correlation coefficient of -0.75. Soluble carbohydrate content increased as the mean temperature decreased and declined as the mean temperature increased, but was independent of a specific temperature. The insoluble carbohydrate content was positively correlated with temperature. Root carbohydrate content also varied with fluctuations in the maximum and minimum temperature, dew point, and total pan evaporation, but not with precipitation.