Modeling the Current-Voltage Characteristics of Charophyte Membranes. II. The Effect of Salinity on Membranes of Lamprothamnium papulosum

Beilby, Mary J.; Shepherd, Virginia A.

doi:10.1007/pl00020977

Cited by 35 publications

(46 citation statements)

References 46 publications

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“…There was residual conductance when both inhibitors were present; this could be due to a ''leak'' conductance, as seen in charophytes (Beilby 1989;Beilby and Shepherd, 2001;Beilby et al in press). Infusion of the inhibitors into the vacuole has no effect on G TP , but it is not clear whether this is because the tonoplast channels are not sensitive to them, or because the inhibitor exposure was too short for it to diffuse through the vacuolar mucilage.…”

Section: Models Of Ion Transportmentioning

confidence: 96%

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Electrophysiology of Turgor Regulation in Marine Siphonous Green Algae

2006

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Abstract. We review electrophysiological measures of turgor regulation in some siphonous green algae, primarily the giant-celled marine algae, Valonia, and Ventricaria, with particular comparison to the well studied charophyte algae Chara and Lamprothamnium. The siphonous green algae have a less negative plasma membrane potential, and are unlikely to have a proton-based chemiosmotic transport system, dominated by active electrogenic K + uptake. We also make note of the unusual cellular structure of the siphonous green algae. Hypertonic stress, due to increased external osmotic pressure, is accompanied by positive-going potential difference (PD), increase in conductance, and slow turgor-regulation. The relationship between these is not yet resolved, but may involve changes in K + conductance (G K ) or active K + transport at both membranes. Hypotonic turgor regulation, in response to decrease external osmotic pressure, is 3 times faster than hypertonic turgor regulation. It is accompanied by a negative-going PD, although conductance also increases. The conductance increase and the magnitude of the PD change are strongly correlated with the magnitude of hypotonic stress.

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Section: Models Of Ion Transportmentioning

confidence: 96%

“…There is an increase in H + -pumping, which drives increased passive K + uptake and Cl ) uptake by H + symport (Beilby & Shepherd, 2001). Valonia and Ventricaria PDs become more positive, possibly due to an increase in active K + uptake at the tonoplast.…”

Section: Comparisons Between Salt-tolerant Charophytes and Valonia/vementioning

confidence: 99%

Electrophysiology of Turgor Regulation in Marine Siphonous Green Algae

2006

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“…Nonetheless, at all salinities studied, some Lamprothamnium cells were in the background or the K + state and the pump did not seem to work at all (Beilby and Shepherd 2001b). These cells were always monitored for good streaming rates to ensure that they were not damaged.…”

Section: Increase In Salinitymentioning

confidence: 94%

“…2). Beilby and Shepherd (2001a) modelled the I/V profiles of Lamprothamnium cells acclimated to salinities ranging from 0.2 to full ASW (artificial sea water). They found that the cells could be in three different states: (1) pump state, (2) background state or (3) K + state (each state displaying typical I/V characteristics, see Chap.…”

Section: Increase In Salinitymentioning

confidence: 99%

Electrophysiology of the Detached Cell Under Stress

Beilby

Casanova

2013

The Physiology of Characean Cells

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This chapter summarises the research on characean detached cells, subjected to calibrated and primarily abiotic types of stress. Responses to touch, wounding, voltage clamp to both depolarised and hyperpolarised potential difference (PD) levels and to osmotic and saline stress are described. Both salt-tolerant and saltsensitive Characeae have been investigated under osmotic and saline stress. Many of the cell responses involve an increase in cytoplasmic calcium concentration. However, the manner of calcium increase is specific to different stressors: mechanical stimulation opens stretch-activated (SA) channels on internal stores, depolarisation to excitation threshold opens IP 6 -activated channels on internal stores, hypo-osmotic stress opens SA channels on internal stores and possibly the vacuole, hyperpolarisation opens channels on the plasma membrane. The increase in the calcium concentration in the cytoplasm opens calcium-activated chloride channels on the plasma membrane (and possibly the tonoplast), leading to an outflow of chloride and depolarisation that can take a form of receptor potential (RPD), action potential (AP) or variation potential (VP). From all these responses, the AP fits the role of a signal: its form is relatively constant and it can propagate speedily from cell to cell. The responses to hyperosmotic and saline stress show interesting differences between salt-tolerant and salt-sensitive Characeae. In salt-tolerant Characeae, the proton pump is activated by both a decrease in turgor and an increase in salinity. The activation by turgor decrease is transient as turgor is regulated, while activation by salt is permanent and graded according to salt concentration. The turgor sensors may be located at the ends of nodal cells. In salt-sensitive Characeae, on the other hand, non-plasmolysing turgor decrease elicits no change in pump activity, while an increase in salinity shuts down the pump and opens H + /OH À channels, depolarising the membrane PD further. Spontaneous APs with long durations and opening of outward rectifying channels lead to a loss of potassium and death. Both salt-sensitive and salt-tolerant Characeae employ Na + /H + antiporter to remove Na + from the cytoplasmic compartment under saline stress and the water channels on the plasma membrane are closed by high osmolarity.

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“…Right panel: In the halophyte S. maritima, the VIC appears to be absent and Na + influx occurs only through the IRC. Large pump activity hyperpolarises the membrane by an increase in Na + concentration (Beilby and Shepherd 2001), so cells must be able to monitor Na + concentration. This activation persists as long as the cells stay in the high salt medium.…”

Section: Ion Channels and Salt Tolerance In Charophytesmentioning

confidence: 99%

The Role of Ion Channels in Plant Salt Tolerance

Amtmann

Beilby²

2010

Ion Channels and Plant Stress Responses

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Salinisation of agricultural land threatens world food production because it exposes crops to low water potential and high concentration of toxic ions in the soil. In particular, all major crops are sensitive to high concentrations of sodium (Na + ). Due to the negative electrical potential inside cells Na + influx into plant roots can occur through ion channels or other membrane transport proteins that facilitate passive diffusion of Na + across the plasma membrane. In this chapter, we discuss the contribution of different types of ion channels to Na + influx. In the first part of the chapter, we recapitulate the basic properties of different types of plant ion channels such as voltage-dependence of gating and relative selectivity for Na + and potassium and build a simple model to assess how these channels contribute to whole-cell ionic current and Na + uptake. In the second part of the chapter, we describe a number of experimental studies that have investigated Na + flux and ion channel currents in different plant species. The combined evidence suggests that salt tolerance in plants is based on the restriction of Na + influx through voltage-independent ion channels. Abbreviations VICVoltage-independent channel IRC Inward-rectifying channel ORC Outward-rectifying channel GHK

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Modeling the Current-Voltage Characteristics of Charophyte Membranes. II. The Effect of Salinity on Membranes of Lamprothamnium papulosum

Cited by 35 publications

References 46 publications

Electrophysiology of Turgor Regulation in Marine Siphonous Green Algae

Electrophysiology of Turgor Regulation in Marine Siphonous Green Algae

Electrophysiology of the Detached Cell Under Stress

The Role of Ion Channels in Plant Salt Tolerance

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