Differential Ion Accumulation and Ion Fluxes in the Mesophyll and Epidermis of Barley

• Published in: Plant physiology (Bethesda) Vol. 122; no. 3; pp. 835 - 844
• Main Authors: Alison J. Karley, Leigh, Roger A., Sanders, Dale
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01.03.2000; American Society of Plant Biologists
• Subjects: Absorption. Translocation of ions and substances. Permeability; Agronomy. Soil science and plant productions; Anions; Barley; Biological and medical sciences; calcium; Calcium - metabolism; Cations; Cell Biology and Signal Transduction; Cell Membrane; Cell Membrane - metabolism; Cell membranes; Cell physiology; chlorides; Economic plant physiology; electrophysiology; Epidermal cells; Epidermis; Fundamental and applied biological sciences. Psychology; Guard cells; Hordeum; Hordeum - metabolism; Hordeum vulgare; inorganic ions; Ion accumulation; Ion Channels; Ion Channels - metabolism; Ion Transport; Leaves; Membrane Potentials; Membranes; Mesophyll; Mesophyll cells; metabolism; Nutrition. Photosynthesis. Respiration. Metabolism; Patch-Clamp Techniques; phosphates; Phosphates - metabolism; Plant cells; Plant Leaves; Plant Leaves - metabolism; Plant physiology and development; plasma membrane; Plasma membrane and permeation; potassium; Potassium - metabolism; Protoplasts; Protoplasts - metabolism; sodium; Sodium - metabolism; Transport processes; Phosphates; Monocotyledones; Calcium; Hordeum vulgare; Cell permeability; Electrophysiology; Tissue specificity; Epidermis; Ionic channel; Plant leaf; Cereal crop; Ionic selectivity; Mesophyll; Sodium; Gramineae; Chlorides; Angiospermae; Plasma membrane; Spermatophyta; Biological accumulation
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.122.3.835

In barley (Hordeum vulgare L.) leaves, differential ion accumulation commonly results in inorganic phosphate (Pi) being confined to the mesophyll and Ca2+ to the epidermis, with preferential epidermal accumulation of Cl-, Na+, and some other ions. The pattern was confirmed in this study for major inorganic anions and cations by analysis of barley leaf protoplasts. The work focused on the extent to which differences in plasma membrane ion transport processes underlie these observations. Ion transport across the plasma membrane of barley epidermal and mesophyll protoplasts was investigated electrophysiologically (by microelectrode impalement and patch clamping) and radiometrically. Data from both approaches suggested that similar types of ion-selective channels and membrane transporters, which catalyze the transport of Ca2+, K+, Na+, and Pi, exist in the plasma membrane of the two cell types. In general, the simple presence or absence of ion transporters could not explain cell-type-specific differences in ion accumulation. However, patch-clamp data suggested that differential regulation of instantaneously activating ion channels in the plasma membrane could explain the preferential accumulation of Na+ in the epidermis.