System Potentials, a Novel Electrical Long-Distance Apoplastic Signal in Plants, Induced by Wounding

• Published in: Plant physiology (Bethesda) 2009-03, Vol.149 (3), p.1593-1600
• Main Authors: Zimmermann, Matthias R, Maischak, Heiko, Mithöfer, Axel, Boland, Wilhelm, Felle, Hubert H
• Format: Article
• Language: English
• Subjects: Action Potentials - drug effects; Biological and medical sciences; Calcium - metabolism; Cell membranes; Depolarization; Electric potential; Electricity; Electrodes; Environmental Stress and Adaptation to Stress; Extracellular Space - drug effects; Extracellular Space - metabolism; Fundamental and applied biological sciences. Psychology; Glycosides - pharmacology; Hordeum - drug effects; Hordeum - physiology; Intracellular Space - drug effects; Intracellular Space - metabolism; Ion Transport - drug effects; Ions; Membrane potential; Plant Leaves - drug effects; Plant Leaves - physiology; Plant physiology and development; Plants; Proton Pumps - metabolism; Pumps; Signal Transduction - drug effects; Vanadates; Vanadates - pharmacology; Vicia faba - drug effects; Vicia faba - physiology
• ISSN: 0032-0889; 1532-2548; 1532-2548
• DOI: 10.1104/pp.108.133884

Systemic signaling was investigated in both a dicot (Vicia faba) and a monocot (Hordeum vulgare) plant. Stimuli were applied to one leaf (S-leaf), and apoplastic responses were monitored on a distant leaf (target; T-leaf) with microelectrodes positioned in substomatal cavities of open stomata. Leaves that had been injured by cutting and to which a variety of cations were subsequently added caused voltage transients at the T-leaf, which are neither action potentials nor variation potentials: with respect to the cell interior, the initial polarity of these voltage transients is hyperpolarizing; they do not obey the all-or-none rule but depend on both the concentration and the type of substance added and propagate at 5 to 10 cm min⁻¹. This response is thought to be due to the stimulation of the plasma membrane H⁺-ATPase, a notion supported by the action of fusicoccin, which also causes such voltage transients to appear on the T-leaf, whereas orthovanadate prevents their propagation. Moreover, apoplastic ion flux analysis reveals that, in contrast to action or variation potentials, all of the investigated ion movements (Ca²⁺, K⁺, H⁺, and Cl⁻) occur after the voltage change begins. We suggest that these wound-induced "system potentials" represent a new type of electrical long-distance signaling in higher plants.