Cell wall-ion interactions: Significance for nutrition of plants and their stress tolerance -- Cell Wall-Ion Interactions -- Boron in the Apoplast of Higher Plants -- Silicon in Plant Nutrition -- Significance of the Root Apoplast for Aluminium Toxicity and Resistance of Maize -- Significance of Polyamines for Pectin-Methylesterase Activity and the ion Dynamics in the Apoplast -- The root apoplast - implication for ion acquisition and Short-distance transport -- The apoplast: A kinetic perspective -- The apoplast of ectomycorrhizal roots - site of nutrient uptake and nutrient exchange between the symbiotic partners -- Chemical compositon of apoplastic transport barriers in roots -- Apoplastic water transport in roots -- Ion uptake from and loading into the apoplast: Characterization of channel properties and relevance for the nutrition of plants -- Long Distance Transport in Plants: Towards Analyses of Regulatory Interactions Between Membrane Transport Systems and Cell Wall Ionic Atmosphere in Vascular Tissues -- The Role of Potassium in Wood Formation of Poplar -- Transport Characteristics of Ion Channels as Influenced by Apoplastic Properties -- Ion Uptake from the Xylem into the Symplasm of the Maize Leaf -- Loading of Ions into the Xylem of the Root -- The significance of the apoplast as a compartment for long-distance transport -- New Tools to Explore the Apoplast -- On-Line Measurements of Ion Relations in the Xylem Sap of Intact Plants -- Dynamic and Nutrient Fluxes in the Xylem -- Relationship Between Apoplastic Nutrient Concentrations and the Long-Distance Transport of Nutrients in the Ricinus communis L. Seedling -- Long-Distance Water Transport Under Controlled Transpirational Conditions: Minimal-Invasive Investigations by Means of Pressure Probes and NMR Imaging -- Changes in Composition of the Xylem Sap as well as in Ion Fluxes in Populus Tremula X Alba L. Xylem In Dependence on Exogenous Factors -- Ion relations in the apoplast of leaves -- Ion Dynamics in the Apoplast of Leaf Cells -- Probing Apoplastic Ion Relations in Vicia Faba as Influenced by Nutrition and Gas Exchange -- The Role of the Leaf Apoplast in Manganese Toxicity and Tolerance in Cowpea (Vigna Unguiculata L. Walp) -- Interaction between Phloem transport and Apoplastic Solute Concentrations -- Investigations of the mechanisms of long-distance transport and ion distribution in the leaf apoplast of vicia faba l -- The dynamics of iron in the leaf apoplast -- Self-Reporting Arabidopsis Thaliana Expressing pH- and [CA2+] - Indicators Unveil Apoplastic Ion Dynamics -- The apoplast compartment for plant-microbe interactions -- Constraints For Endophytic Bacteria -- The Apoplast of Norway Spruce (Picea Abies) Needles as Habitat and Reaction Compartment for Autotrophic Nitrifiers -- The Rice Apoplast as a Habitat for Endophytic N2-Fixing Bacteria -- The Apoplast of Indeterminate Legume Nodules: Compartment for Transport of Amino Acids, Amides and Sugars?. It was the botanist Ernst Münch, who separated the plant into two principal compartments, the "dead" apoplast and the living symplast. Only during the last 20 years cell walls attracted the interest of a broader group of plant scientists. We know today that apoplastic functions are much more diverse. The apoplast may be considered as "the internal physiological environment of plant bodies", that essentially maintains homeostasis. The term 'cell wall' may be misleading, since the chemical and physical properties of cell walls are not fixed but rapidly respond to environmental stimuli. This is why the term "extracellular matrix" may be more appropriate. The book summarizes the experimental work conducted during a trans-disciplinary research programme funded for six years by the German Research Foundation. In their contributions, the authors representing outstanding German scientists from such different disciplines as Physics, Biochemistry, Plant Nutrition, Botany, and Molecular Biology not only report original research but also review the state of knowledge in their particular research fields: nutrient acquisition, short and long distance (xylem) transport, tolerance of nutrient deficiencies and mineral toxicities, and the role of micro-organisms colonizing the apoplast. Introductory remarks are written to each of the chapters by internationally highly recognized scientists in their research areas.