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Zinc and salinity effects on membrane transport in Chara connivens
Author(s) -
RYGOL J.,
ARNOLD W. M.,
ZIMMERMANN U.
Publication year - 1992
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/j.1365-3040.1992.tb01454.x
Subject(s) - chara , salinity , chemistry , zinc , nuclear chemistry , analytical chemistry (journal) , sodium , cell permeability , permeability (electromagnetism) , mole , membrane , potassium , zoology , botany , environmental chemistry , biochemistry , ecology , biology , organic chemistry
Pressure‐probe measurements showed that the pressure relaxation of internodal cells of the freshwater alga Chara connivens slowed considerably when 1–5 mol m −3 Zn 2+ , or more especially Zn 2+ and 75 mol m −3 NaCl, were present in the medium for periods of 1 h or longer. These results indicate that the water permeability of the Chara membrane is decreased by Zn 2+ , and that this effect is enhanced by 75 mol m −3 NaCl. Specific values taken after 375 min exposure were: 5 mol m −3 Zn 2+ and 75 mol m −3 NaCl caused the half‐time for bulk water movement to increase from 7·8±2·3 to 79·5±5·4s, corresponding to a decrease in the hydraulic conductivity (Lp) from (13·0±3·3) × 10 −7 m s −1 mPa −1 to (1·25±0·23) × 10 −7 m s −1 MPa −1 (mean±S.D., n = 10). These changes are not seen in the presence of NaCl alone, and to a reduced extent in the presence of 5 mol m −3 Zn 2+ alone (after 375 min, Lp was (2·4±0·1) × 10 −7 m s −1 MPa −1 , mean±S.D., n = 6). Ca 2+ cannot substitute for Zn 2+ , but seems to competitively inhibit Zn 2+ . There was another, kinetically distinct effect of Zn 2+ : the ingress of Na + within 15 min of exposure to 75 mol m −3 NaCl is halved by the presence of 1–5 mol m −3 Zn 2+ , although internal osmolality is little changed by Zn 2+ . In spite of this, Zn 2+ does not exert the long‐term protection against NaCl that has been reported for Ca 2+ . Depending on the concentration of Zn 2+ and the duration of the exposure, the effects on water permeability were fully or partly reversible within 24–48 h. The mechanism of these changes is difficult to identify. One possibility is a zinc‐induced restriction of trans‐membrane channels to give single‐file channels which can be blocked by salt.