Distribution of 14C-sugars from 14CO2 in healthy and leaf-rust-infected poplar leaves

Abstract

Three poplar clones, Populus deltoides angulata (resistant), P. deltoides missouriensis (susceptible), and P. “Kamabuchi-1” (variable in susceptibility according to the growing season) were inoculated with uredospores of Melampsora larici-populina, incubated for 9 days, and then cuttings from healthy and infected plants were fed with 14CO2 for 20 hours.In healthy and rusted leaves of these clones, at least six kinds of sugars, sucrose, glucose, fructose, raffinose (?) and two other unidentified sugars, were detected on the autoradio-chromatograms. The specific radioactivity of each sugar generally increased in rusted leaves with a few exceptions, whereas there were remarkable differences in the increasing degree of specific radioactivity among sugar fractions.Labeling of sucrose, glucose and fructose with 14C from 14CO2 increased by rust infection, and the degree of the increase was conspicuous in P. deltoides missouriensis, while it was insignificant in P. deltoides angulata. A general increase in both total and specific radio-activity of sucrose may suggest the possibility of stimulated photosynthesis in rusted leaves.The degree of increase in the specific radioactivity of glucose and fructose were almost equal in rusted leaves of P. deltoides angulata, whereas particular increases were observed for glucose in P. deltoides missouriensis and for fructose in P. “Kamabuchi”, respectively. This fact would suggest that in rusted leaves of the latter two clones the disturbance of carbohydrate metabolism incited by rust infection is still continued, and that there are considerable differences between two clones concerning the pathway of carbohydrate metabolism in infected leaves.