I. Membranes and Water Transport -- Plant Aquaporins: Roles in Water Homeostasis, Nutrition, and Signaling Processes -- II. Signaling Related to Ion Transport -- Plant Proton Pumps: Regulatory Circuits Involving H+ PATPase and H+-PPase -- Na+ and K+ Transporters in Plant Signaling -- Fe2+ Transport and Signaling in Plants -- Ca2+ Pumps and Ca2+ Antiporters in Plant Development -- III. Nutrient Transport -- NO3- Transporters and Root Architecture -- Sensing and Signaling of PO43- -- Sucrose Transporters and Plant Development -- IV. Signaling Molecules -- Auxin Transporters Controlling Plant Development -- V. Membrane structures and development, trafficking and lipid-transporter interactions -- V-ATPases: Rotary Engines for Transport and Traffic -- Type IV (P4) and V (P5) P-ATPases in Lipid Translocation and Membrane Trafficking -- Peroxisomal Transport Systems: Roles in Signaling and Metabolism -- Regulation of Plant Transporters by Lipids and Microdomains. Due to their sessile lifestyle, plants need to efficiently adapt to changing environmental conditions during their life cycle. Nutrient acquisition from the soil has to be able to adapt to considerable fluctuations in concentrations to ensure adequate distribution between tissues, cells and organelles. The storage and retrieval of nutrients, metabolites or toxic substances in vacuoles plays an important part in cellular homeostasis in plants. The long-range transport and maintenance of turgor is critically dependent on the availability of water and rate of evaporation, while at the same time photosynthetic products have to be transported to all plant parts. As a result plants contain a large number of ATP-dependent pumps and secondary transporters that, in order to adapt to the changing environment, need to be regulated by a complex network of sensing and signaling mechanisms. Plants share many basic elements of signal transduction with animals, but also contain plant-specific signaling molecules and mechanisms. In this volume, the role of transporters and pumps in the regulation of movement, long-range transport and compartmentalization of water, solutes, nutrients and classical signaling molecules is highlighted, and the function, regulation and membrane-transporter interaction and their roles in plant signaling controlling plant physiology and development are discussed.