This book is addressed to all biologists seeking a review of the various transport processes of minerals and organic substances in plants from the level of cell organelles to the longer-distance movements in the largest trees. It is directed toward students having had some elementary physiol- ogy, but the attempt has been made to provide information of interest on the frontiers of current research. Doing this comprehensively, we wished to consider all of the points of view that appeared to be important; on the other hand, space and time were limited. Therefore, the presentation had to strike an intermediate ground between the style of a textbook giving representative treatments of selected problems and a comprehensive ref- erence book covering all ramifications. The reader will notice that the pendulum will swing more toward one and then to the other. We did not want to avoid, and we felt it was not appropriate to neglect completely our own special research interests, which led to some emphasis on certain subjects. The immediate origin of the book is the Heidelberger Taschenbuch 125 (HTB 125) Stofftransport der Pflanzen by U. L. (1973), which in turn was preceded by an earlier work, Aktiver Transport: Kurzstreckentransport bei Pflanzen Protoplasmatologia vol. VIII/7 b by U . L. (1969). At the Li- verpool Workshop on Ion Transport in 1972 organized by W.