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Title: Inorganic carbon uptake during photosynthesis. II. Uptake by isolated Asparagus mesophyll cells during isotopic disequilibrium. [Asparagus sprengeri]

Abstract

The species of inorganic carbon (CO/sub 2/ or HCO/sub 3//sup -/) taken up as a source of substrate for photosynthetic fixation by isolated Asparagus sprengeri mesophyll cells is investigated. Discrimination between CO/sub 2/ or HCO/sub 3//sup -/ transport, during steady state photosynthesis, is achieved by monitoring the changes (by /sup 14/C fixation) which occur in the specific activity of the intracellular pool of inorganic carbon when the inorganic carbon present in the suspending medium is in a state of isotopic disequilibrium. Quantitative comparisons between theoretical (CO/sub 2/ or HCO/sub 3//sup -/ transport) and experimental time-courses of /sup 14/C incorporation, over the pH range of 5.2 to 7.5, indicate that the specific activity of extracellular CO/sub 2/, rather than HCO/sub 3//sup -/, is the appropriate predictor of the intracellular specific activity. It is concluded, therefore, that CO/sub 2/ is the major source of exogenous inorganic carbon taken up by Asparagus cells. However, at high pH (8.5), a component of net DIC uptake may be attributable to HCO/sub 3//sup -/ transport, as the incorporation of /sup 14/C during isotopic disequilibrium exceeds the maximum possible incorporation predicted on the basis of CO/sub 2/ uptake alone. The contribution of HCO/sub 3//sup -/ to netmore » inorganic carbon uptake (pH 8.5) is variable, ranging from 5 to 16%, but is independent of the extracellular HCO/sub 3//sup -/ concentration. The evidence for direct HCO/sub 3//sup -/ transport is subject to alternative explanations and must, therefore, be regarded as equivocal. Nonlinear regression analysis of the rate of /sup 14/C incorporation as a function of time indicates the presence of a small extracellular resistance to the diffusion of CO/sub 2/, which is partially alleviated by a high extracellular concentration of HCO/sub 3//sup -/.« less

Authors:
; ;
Publication Date:
Research Org.:
York Univ., Downsview, Ontario
OSTI Identifier:
7024324
Resource Type:
Journal Article
Journal Name:
Plant Physiol.; (United States)
Additional Journal Information:
Journal Volume: 80:4
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; CARBON DIOXIDE; UPTAKE; CARBONIC ACID; PLANT CELLS; PHOTOSYNTHESIS; CARBON 14 COMPOUNDS; CARBON DIOXIDE FIXATION; MEASURING METHODS; PH VALUE; REGRESSION ANALYSIS; SOLUTES; TRACER TECHNIQUES; CARBON COMPOUNDS; CARBON OXIDES; CHALCOGENIDES; CHEMICAL REACTIONS; HYDROGEN COMPOUNDS; INORGANIC ACIDS; ISOTOPE APPLICATIONS; LABELLED COMPOUNDS; MATHEMATICS; OXIDES; OXYGEN COMPOUNDS; PHOTOCHEMICAL REACTIONS; STATISTICS; SYNTHESIS; 550501* - Metabolism- Tracer Techniques

Citation Formats

Espie, G S, Owttrim, G W, and Colman, B. Inorganic carbon uptake during photosynthesis. II. Uptake by isolated Asparagus mesophyll cells during isotopic disequilibrium. [Asparagus sprengeri]. United States: N. p., 1986. Web.
Espie, G S, Owttrim, G W, & Colman, B. Inorganic carbon uptake during photosynthesis. II. Uptake by isolated Asparagus mesophyll cells during isotopic disequilibrium. [Asparagus sprengeri]. United States.
Espie, G S, Owttrim, G W, and Colman, B. 1986. "Inorganic carbon uptake during photosynthesis. II. Uptake by isolated Asparagus mesophyll cells during isotopic disequilibrium. [Asparagus sprengeri]". United States.
@article{osti_7024324,
title = {Inorganic carbon uptake during photosynthesis. II. Uptake by isolated Asparagus mesophyll cells during isotopic disequilibrium. [Asparagus sprengeri]},
author = {Espie, G S and Owttrim, G W and Colman, B},
abstractNote = {The species of inorganic carbon (CO/sub 2/ or HCO/sub 3//sup -/) taken up as a source of substrate for photosynthetic fixation by isolated Asparagus sprengeri mesophyll cells is investigated. Discrimination between CO/sub 2/ or HCO/sub 3//sup -/ transport, during steady state photosynthesis, is achieved by monitoring the changes (by /sup 14/C fixation) which occur in the specific activity of the intracellular pool of inorganic carbon when the inorganic carbon present in the suspending medium is in a state of isotopic disequilibrium. Quantitative comparisons between theoretical (CO/sub 2/ or HCO/sub 3//sup -/ transport) and experimental time-courses of /sup 14/C incorporation, over the pH range of 5.2 to 7.5, indicate that the specific activity of extracellular CO/sub 2/, rather than HCO/sub 3//sup -/, is the appropriate predictor of the intracellular specific activity. It is concluded, therefore, that CO/sub 2/ is the major source of exogenous inorganic carbon taken up by Asparagus cells. However, at high pH (8.5), a component of net DIC uptake may be attributable to HCO/sub 3//sup -/ transport, as the incorporation of /sup 14/C during isotopic disequilibrium exceeds the maximum possible incorporation predicted on the basis of CO/sub 2/ uptake alone. The contribution of HCO/sub 3//sup -/ to net inorganic carbon uptake (pH 8.5) is variable, ranging from 5 to 16%, but is independent of the extracellular HCO/sub 3//sup -/ concentration. The evidence for direct HCO/sub 3//sup -/ transport is subject to alternative explanations and must, therefore, be regarded as equivocal. Nonlinear regression analysis of the rate of /sup 14/C incorporation as a function of time indicates the presence of a small extracellular resistance to the diffusion of CO/sub 2/, which is partially alleviated by a high extracellular concentration of HCO/sub 3//sup -/.},
doi = {},
url = {https://www.osti.gov/biblio/7024324}, journal = {Plant Physiol.; (United States)},
number = ,
volume = 80:4,
place = {United States},
year = {Tue Apr 01 00:00:00 EST 1986},
month = {Tue Apr 01 00:00:00 EST 1986}
}