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The uptake of inorganic carbon by freshwater plants
Author(s) -
WALKER N. A.
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 - 10.1111/1365-3040.ep11612118
Subject(s) - bicarbonate , assimilation (phonology) , photosynthesis , diffusion , total inorganic carbon , carbon assimilation , alkalinity , chemistry , dissolved organic carbon , membrane , facilitated diffusion , carbon fibers , environmental chemistry , biophysics , botany , ecology , carbon dioxide , biology , biochemistry , materials science , composite number , composite material , philosophy , linguistics , physics , organic chemistry , thermodynamics
. The uptake of bicarbonate for photosynthetic assimilation by charophyte plants uses a chemiosmotic mechanism involving primary outward active transport of H + in ‘acid zones’ of the membrane, and passive H + re‐entry in spatially separate ‘alkaline’ zones. In the process large electric currents circulate in the medium, and large local pH changes occur; bicarbonate ions, diffusing inwards across the unstirred layer of medium, encounter a number of competing mechanisms for the transfer of the carbon across the membrane. These are:i. transport of H 2 CO 3 by diffusion ii. transport of CO 2 by diffusion; or iii. co‐transport of HCO 3 and H + .The decision amongst these mechanisms is not yet possible. There are parallels between the charophytes and aquatic angiosperms that are indicated, and contrasts with the chlorophytes.