Halophytes are plants that complete their life cycle in saline environments. Halophytes can therefore be viewed as potential gene sources for genetic manipulation of economically important crop plants. In this study the influence of salinity on potential difference (PD) and surface pH of root cortical cells was investigated. The effect of the metabolic inhibitor, potassium cyanide (KCN), on PD of the root cells was also investigated. A study of the electrophysiological characteristics of the membrane of the root cortical cells showed that there were two components to the root cell PD. One component (diffusional) was affected by the increasing NaCl concentration in the growth medium, while the other component (electrogenic) remained unaffected by the NaCl concentration up to 200 mol m^-3. There is evidence to suggest that this electrogenic component of the PD was maintained by an efflux pump which presumably controls ion uptake and indirectly growth. It is concluded that this electrogenic efflux pump is a major factor contributing to salt tolerance in Sesuvium portulacastrum.

Key words: Electrogenic pumps, halophyte, membrane potential difference, salinity, Sesuvium portulacastrum.

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