Sokołowska and Zagrska-Marek, in order to determine whether they could visually trace the pathways of solutes as those solutes travel up the living cells of the xylem network, cut 1- to 3-year-old branches from maple (Acer pseudoplatanus) and poplar (Populus tremula x P. tremuloides) trees and immersed the cut ends in a solution containing one of several fluorescent dyes.
After leaving the branches in the dye solutions for 3 to 7 days (adequate time for the dye to move a substantial distance), the authors cut cross- and tangential sections of the branches and found that dye was present in the living cells of both the radial and axial xylem parenchyma and ray and fusiform cambial cellsclear evidence that symplasmic transport occurred in both the secondary xylem and the cambial tissues. Moreover, dye was not only clearly seen in the cytoplasm of the cells, but also in the cytoplasmic bridges spanning walls between adjacent cells, confirming intercellular movement.
"Through the fluorescent marker application, we have successfully been able to visualize the transportation routes of nutrients or signaling molecules, which are regulated by changing states of cell-to-cell conductivity in time and in space," said Sokołowska. "They can be compared to traffic lights on crossroads, which control the road traffic and highway networks, ensuring fast and smooth transport between distant places."
Moreover, by using different dyes, the authors were able to see differences between the apoplasmic and symplasmic pathways. Although the apoplasmic dye was present
|Contact: Richard Hund|
American Journal of Botany