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Regulation of nitrate uptake into Chara corallina cells via NH + 4 stimulation of NO − 3 efflux
Author(s) -
DEANEDRUMMOND C.E.
Publication year - 1985
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.1365-3040.1985.tb01216.x
Subject(s) - efflux , chemistry , electrochemistry , stimulation , nitrate , nernst equation , analytical chemistry (journal) , biophysics , nuclear chemistry , chromatography , biochemistry , biology , electrode , organic chemistry , neuroscience
. Net NO 3 uptake by NO − 3 deficient Chara cells was used to calculate [NO − 3 ] c assuming that the cytoplasm occupies 10% total volume and that nitrate reduction and storage are negligible (i.e. maximum [NO − 3 ] c was calculated). A linear relationship was found between NO − 3 efflux and [NO − 3 ] c . There was an initial burst of NO − 3 efflux when NH + 4 was added, followed by a slower efflux rate which matched influx rate such that net NO − 3 uptake was zero. Over 50% of NO − 3 that had been taken up in 2 h was lost within the first 5 min of NH + 4 addition. The Nernst equation was used to predict the direction of the electrochemical driving force for NO − 3 entry. Under the experimental conditions used NO − 3 efflux is actively transported. The differential involvement of both NO − 3 influx and NO − 3 efflux in the regulation of NO − 3 uptake is discussed and a model is proposed to account for these results which envisages discrete NO − 3 influx and NO − 3 efflux carriers.