Ion Transport at the Plant Plasma Membrane

Abstract

Membrane transport plays a fundamental role in virtually every aspect of homeostasis, signalling, growth and development in plants. At the plasma membrane, the boundary with the outside world, ion and solute fluxes underpin inorganic mineral nutrient uptake, they trigger rapid changes in second messengers such as cytosolic‐free Ca 2+ concentrations, and they power the osmotic gradients that drive cell expansion, to name just a few roles. Our understanding of the transporters – the ion pumps that generate an H + electrochemical driving force, H + ion‐coupled symport and antiport systems, and ion channels – now, more than ever, builds on developments in molecular genetics, protein chemistry and crystallography to gain insights into the fine structure and mechanics of these remarkable enzymes. Even so, it is the interface with the biophysical detail of ion transport that drives scientific enquiry in the field and will continue to be essential in informing both the most fundamental research as well as efforts to apply the knowledge gained in resolving some of the dilemmas that face society today.

Electrophysiology of Woody Plants

“…All plant cells are surrounded by a plasma membrane (Murphy et al, 2010), composed of a lipid bilayer, with a variety of molecular structures embedded in it, known generically as ion channels and electrogenic pumps (Hedrich & Schroeder, 1989). Electrochemical excitation is caused by ionic fluxes through the cell plasma membrane (Knudsen, 2002;Blatt, 2008), creating an electric charge modification in the membrane itself, as well as a differential charge on either side. This trans -membrane potential is the difference in voltage (or electrical potential difference) between the interior and exterior of a cell (V interior − V exterior ).…”

“…This process is involved in the simultaneous symport of carbohydrates and amino acids into the cell, which are produced at different plant tissues as photosynthetic derivatives. Other electrogenic ion pumps described for plant cell plasma membranes are related to ion and solute fluxes, underpinning inorganic mineral nutrient uptake; they trigger rapid changes in secondary messengers such as cytosolic-free Ca +2 concentrations, and also power the osmotic gradients that drive cell expansion (Schroeder & Thuleau 1991;Gelli & Blumwald, 1997;Zimmermann et al, 1997;Bonza et al, 2001;Sanders, 2002;Blatt, 2008;Lautner & Fromm, 2010). The K +1 -transporting ATPase, also embedded in the cell plasma membrane, enables the onset of different ion concentrations (and therefore electrical charge) on the intracellular and extracellular sides of the membrane (Maathuis & Sanders, 1997).…”