Solute transport in plants, translocation, primarily occurs in the phloem, but it can occur in the xylem. Solute Transport in the Xylem. See table on overhead .
Substances move at different rates depending on matrix effects, metabolic needs, etc.
Solute Transport in the Phloem . Radiotracer studies in which leaves are briefly exposed to 14 C-labeled carbon dioxide show that radioactive photosynthates are localized in the phloem. Aphids Don't Suck. Surprisingly, the phloem doesn't seal itself in response. Physiologists collect the honeydew and identify its composition.