Our objective was to determine if the chlorsulfuron-induced reduction in assimilate export from leaves can be attributed to a shortage of carbohydrates. Treated canola leaves showed no reduction in carbon fixation or carbohydrate production during the first 24 h, but they exuded only 17 to 27% of the amount of sucrose exuded by corresponding control leaves. Exposure of the leaves to higher concentrations of CO2(500 vs. 350 μl L−1) resulted in greater net carbon exchange and higher starch content, but failed to overcome the reduction in sucrose export, presumably because of increased carbon allocation to starch.
Precipitation thresholds regulate net carbon exchange at the continental scale
