Salinity Effects on the Activity of Plasma Membrane H+and Ca2+Transporters in Bean Leaf Mesophyll: Masking Role of the Cell Wall

Net fluxes of H a and Ca 2a were measured in the mesophyll tissue of broad bean (Vicia faba L.) leaves and in protoplasts derived from these cells. NaCl at 90 mM enhanced H a extrusion in both protoplasts and tissue, but in diAerent ways. Proton extrusion was inhibited by vanadate, suggesting the involvement of the plasma membrane H a ATPase in cell responses to salinity. There was virtually no eAect of NaCl on the net Ca 2a flux in protoplasts, while in the tissue a large transient Ca 2a eCux followed the salt treatment. Salt-induced Ca 2a eCux was essentially independent of external Ca2a concentrations in the range 0. 1t o 10 mM. Also, Ca2a flux responses were ‘saturated’ above 50 mM NaCl. It is suggested that almost all the measured Ca2a flux originates from Naa/Ca2a and Ha/Ca2a ion exchange in the cell wall. This conclusion was supported by the results of modelling cation exchange in the cell wall. # 2000 Annals of Botany Company

[1]  A. Galston,et al.  Osmotically induced changes in electrical properties of plant protoplast membranes. , 1977, Science.

[2]  R. M. Spanswick,et al.  Characterization of the Electrogenicity of Soybean (Glycine max L.) Roots : ATP Dependence and Effect of ATPase Inhibitors. , 1984, Plant physiology.

[3]  A. Läuchli,et al.  Displacement of Ca2+ by Na+ from the Plasmalemma of Root Cells A Primary Response to Salt Stress? , 1985 .

[4]  C. Willmer,et al.  Pressure Effects on Membrane Potentials of Mesophyll Cell Protoplasts and Epidermal Cell Protoplasts of Commelina communis L. , 1986 .

[5]  J. Lynch,et al.  Influx of na, k, and ca into roots of salt-stressed cotton seedlings : effects of supplemental ca. , 1987, Plant physiology.

[6]  J. Lynch,et al.  Salinity reduces membrane-associated calcium in corn root protoplasts. , 1987, Plant physiology.

[7]  J. Dainty,et al.  Ion behavior in plant cell walls. I. Characterization of the Sphagnum russowii cell wall ion exchanger , 1989 .

[8]  J. Lynch,et al.  Salinity stress increases cytoplasmic ca activity in maize root protoplasts. , 1989, Plant physiology.

[9]  P. M. Neumann,et al.  Sodium does not compete with calcium in saturating plasma membrane sites regulating na influx in salinized maize roots. , 1991, Plant physiology.

[10]  P. Ryan,et al.  Rapid calcium exchange for protons and potassium in cell walls of Chara , 1992 .

[11]  E. Ohta,et al.  Stimulation of the Extrusion of Protons and H+-ATPase Activities with the Decline in Pyrophosphatase Activity of the Tonoplast in Intact Mung Bean Roots under High-NaCl Stress and Its Relation to External Levels of Ca2+ Ions , 1992 .

[12]  Z. Rengel,et al.  The role of calcium in salt toxicity , 1992 .

[13]  J. Ding,et al.  Mechanosensory calcium-selective cation channels in epidermal cells. , 1993, The Plant journal : for cell and molecular biology.

[14]  Y. Hiramoto,et al.  Short‐term regulation of cytosolic Ca2+, cytosolic pH and vacuolar pH under NaCl stress in the charophyte alga Nitellopsis obtusa , 1996 .

[15]  S. Assmann,et al.  Laser Microsurgery of Higher Plant Cell Walls Permits Patch-Clamp Access , 1996, Plant physiology.

[16]  J. O'leary,et al.  Increased vacuolar and plasma membrane H+-ATPase activities in Salicornia bigelovii Torr. in response to NaCl , 1996 .

[17]  G. Cramer,et al.  Osmotic stress and abscisic acid reduce cytosolic calcium activities in roots of Arabidopsis thaliana , 1996 .

[18]  J. Ehleringer,et al.  Carbon Isotopic Fractionation Does Not Occur during Dark Respiration in C3 and C4 Plants , 1997, Plant physiology.

[19]  S. Shabala,et al.  Oscillations in H+ and Ca2+ Ion Fluxes around the Elongation Region of Corn Roots and Effects of External pH , 1997, Plant physiology.

[20]  P. White.  Calcium Channels in the Plasma Membrane of Root Cells , 1998 .

[21]  S. Shabala,et al.  Protoplast ion fluxes: their measurement and variation with time, position and osmoticum , 1998, Planta.

[22]  Shabala,et al.  Light-induced changes in hydrogen, calcium, potassium, and chloride ion fluxes and concentrations from the mesophyll and epidermal tissues of bean leaves. Understanding the ionic basis of light-induced bioelectrogenesis , 1999, Plant physiology.

[23]  H. Bohnert,et al.  Salt stress in Mesembryanthemum crystallinum L. cell suspensions activates adaptive mechanisms similar to those observed in the whole plant , 1999, Planta.