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Involvement of calcium ion in turgor regulation upon hypotonic treatment in Lamprothamnium succinctum
Author(s) -
OKAZAKI Y.,
TAZAWA M.
Publication year - 1986
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/1365-3040.ep11611622
Subject(s) - turgor pressure , depolarization , tonicity , biophysics , conductance , calcium , chemistry , membrane , membrane potential , osmotic pressure , biochemistry , biology , mathematics , organic chemistry , combinatorics
When internodal cells of Lamprothamnium succinetum were exposed to a hypotonic medium containing more than 1 mol m −3 Ca 2+ , the elevated turgor pressure decreased and reached a steady state within 30–60 min. The hypotonic treatment caused the membrane potential to depolarize, with a time lag of ca. 1 min. The membrane conductance increased transiently with the same time lag and reached a peak value within 2–3 min. When the external Ca 2+ concentration was lowered to 0.01 mol m −3 , both turgor regulation and change in the membrane conductance were strongly inhibited, although the membrane depolarization was not affected. When the Ca2+ level was returned to the normal level, the cells recovered their ability for turgor regulation and the membrane conductance attained a peak value after ca. 15–30 s. This response time is definitely shorter than that needed for the conductance change in cells exposed to a hypotonic medium having a normal level of Ca 2+ from the beginning. We thus conclude that at least two sequential processes are involved in turgor regulation: a Ca 2+ ‐independent process, followed by a Ca 2+ ‐dependent process.