The ambition of the work presented in this thesis is to address the need for nondestructive, repeatable measurements of long-distance transport of photosynthates through the phloem vascular tissue of woody plants. Quantification of long-distance phloem transport is believed to be able to provide information relevant to the forest carbon cycle as well as to a plant's response to changes in its environment. However, due to the fragility of the tissue, invasive techniques such as used routinely for the monitoring of water flow through the xylem are not applicable. Consequently, very little field data on phloem transport rates and patterns are currently available.