Salt tolerance in Nitellopsis obtusa

M. Katsuhara, M. Tazawa

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52 Citations (Scopus)


The mechanism of salt tolerance was studied using isolated internodal cells of the charophyte Nitellopsis obtusa grown in fresh water. When 100 mM NaCl was added to artificial pond water (0.1 mM each of NaCl, KC1, CaCl2), no cell survived for more than one day. Within the first 30 minutes, membrane potential (Em) depolarized and membrane resistance (Rm) decreased markedly. Simultaneously, cytoplasmic Na+ increased and K+ decreased greatly. At steady state the increase in Na+ content was roughly equal to the decrease in K+ content. The Cl- content of the cytoplasm did not change. These results suggest that Na+ enters the cytoplasm by exchange with cytoplasmic K+. Both the entry of Na+ and the exit of K+ are assumed to be passive and the latter being caused by membrane depolarization. Vacuolar K+, Na+, and Cl- remained virtually constant, suggesting that rapid influx of Na+ from the cytoplasm did not occur. In 100 mM NaCl containing 10 mM CaCl2, membrane depolarization, membrane resistance decrease and changes in cytoplasmic [Na+] and [K+] did not occur, and cells survived for many days. When cells treated with 100 mM NaCl were transferred within 1 hour to 100 mM NaCl containing 10 mM CaCl2, Em decreased, Rm increased, cytoplasmic Na+ and K+ returned to their initial levels, and cells survived. Two possible mechanisms for the role of Ca2+ in salt tolerance in Nitellopsis are discussed; one a reduction in plasmalemma permeability to Na+ and the other a stimulation of active Na+-extrusion.

Original languageEnglish
Pages (from-to)155-161
Number of pages7
Issue number2-3
Publication statusPublished - Jun 1 1986
Externally publishedYes


  • Calcium ion
  • Membrane conductance
  • Membrane potential
  • Na/K exchange
  • Nitellopsis obtusa
  • Salt tolerance

ASJC Scopus subject areas

  • Plant Science
  • Cell Biology


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