Water-Soluble Carbohydrates in Johnsongrass

Abstract

Studies were conducted to characterize qualitatively and quantitatively the water-soluble carbohydrates in johnsongrass[Sorghum halepense(L.) Pers.]. Glucose, fructose, and sucrose were the only sugars detected in other than trace amounts in leaves, culms, or rhizomes. Sucrose was the major storage carbohydrate, although glucose and fructose were present throughout most of the life cycle in both leaves and rhizomes. Levels of glucose, fructose, and sucrose in rhizomes were maximum when plants began flowering and minimum at 10 to 30 days after plant emergence. Glucose, fructose, and sucrose were at a maximum in leaves within 30 days after plant emergence. Glucose was present only in trace amounts in leaves for about 10 days during initial flowering; fructose was at a maximum at that time. Sucrose in leaves occurred in greatest quantities soon after plant emergence, immediately before flowering, and after flowering. Leaf blades and sheaths contained nearly equal concentrations of carbohydrates, but stems contained greater concentrations than leaves. Basal shoots and secondary culms from nodes on primary culms contained greater concentrations of carbohydrates than leaves on primary culms. Regrowth from clipped shoots had significantly higher concentrations of glucose and sucrose than did unclipped shoots. Rhizomes of clipped plants had significantly less sucrose but more glucose than rhizomes of unclipped plants.