Plasma membrane transport in context — making sense out of complexity

Major advances in our understanding of the transport of inorganic nutrient ions across plant plasma membranes have emerged from recent studies on the control of the dominant H +-pumping ATPase and from identification of a range of new transporters for divalent cations, potassium, phosphate and nitrate. In many cases, multiple transporter isoforms have been described. An appreciation of the physiological roles of these transporters demands combined genetic and physiological approaches, which, in the case of an outward rectifying K + channel, have already been used to yield an intriguing insight into root-mediated K + release into the xylem. In this review we attempt to place some of those developments in a physiological context.