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The effect of CO 2 on potassium transport by Chlorella fusca
Author(s) -
TROMBALLA H. W.
Publication year - 1983
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.1365-3040.1983.tb01166.x
Subject(s) - dcmu , chlorella , potassium , chemistry , efflux , intracellular , biophysics , nuclear chemistry , membrane transport , analytical chemistry (journal) , medicinal chemistry , photosynthesis , biochemistry , chromatography , algae , membrane , botany , biology , photosystem ii , organic chemistry
. The effect of CO 2 on net K + uptake by Chlorella fusca grown on high CO 2 levels was examined by passing 1.5% CO 2 through algal suspensions gassed previously with air or CO 2 ‐free air Addition of CO 2 in the light caused a large net uptake of K + (initial velocity 4.2–9.2 mmol s −1 m −3 cells) which decreased the concentration of K + in the supernatant from 0.1–0.2 mol m −3 to 3–10 mmol m −3 . In the dark and in the presence of 30 mmol m −3 DCMU, no effects were found. Measurement or the unidirectional K + fluxes by using 86 Rb + as a label showed that in the presence of 1.5% CO 2 , influx of K + was increased by a factor of 2–4 while efflux was inhibited completely. CO 2 hyperpolarized the membrane potential (determined through TPP + uptake) from –120mV to –130 mV which could not explain the more than 15,000‐fold K + accumulations. In the light, CO 2 lowered the intracellular pH (determined with DMO) by 0.5 units. In the dark and in the presence of DCMU only, a small acidification of 0.1 units was found. During the first 15 min after addition of CO 2 the malate content of the cells increased from 0.7 to 1.5 mol m −3 packed cells. On the basis of these and earlier results, CO 2 ‐induced net K + uptake is interpreted as a stimulation of an electroneutral ATP‐dependent K + /H + exchange at the plasmalemma. This exchange acts as a ‘pHstat’ by reducing the intracellular acidification caused by production of acidic assimilation products.