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Control of C4 photosynthesis: effects of reduced activities of phosphoenolpyruvate carboxylase on CO2 assimilation in Amaranthus edulis L.

Bailey, Karen J. and Battistelli, Alberto and Dever, Louisa V. and Lea, Peter John and Leegood, Richard C. (2000) Control of C4 photosynthesis: effects of reduced activities of phosphoenolpyruvate carboxylase on CO2 assimilation in Amaranthus edulis L. Journal of Experimental Botany, 51 (Specia). pp. 339-346. ISSN 1460-2431

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Abstract

Heterozygous mutants of Amaranthus edulis deficient in PEP carboxylase (PEPC) have been used to study the control of photosynthetic carbon assimilation. A reduction in PEPC activity led to a decrease in the initial slope of the relationship between the CO2 assimilation rate and the intercellular CO2 concentration and to a decrease in photosynthesis at high light intensities, consistent with a decrease in the capacity of the C4 cycle in high light. PEPC exerted appreciable control on photosynthetic flux in the wild-type, with a relatively high flux control coefficient of 0.35 in saturating light and ambient CO2. The flux control coefficient was decreased in low light or increased in low CO2 or in plants containing lower PEPC activity. However, the rate of CO2 assimilation decreased down to about 55% PEPC, followed by an up-turn in the light-saturated photosynthetic rate as PEPC was further reduced, suggesting the existence of a mechanism that compensates for the loss of PEPC activity. The amounts of photosynthetic metabolites, including glycine and serine, also showed a biphasic response to decreasing PEPC. There was a linear relationship between the activity of PEPC and the activation state of the enzyme. A possible mechanism of compensation involving photorespiratory intermediates is discussed.

Item Type: Article
Journal or Publication Title: Journal of Experimental Botany
Uncontrolled Keywords: C4 plants ; Amaranthus edulis ; phosphoenolpyruvate carboxylase ; CO2 assimilation ; control of photosynthesis.
Subjects: Q Science > QH Natural history > QH301 Biology
Departments: Faculty of Science and Technology > Lancaster Environment Centre
ID Code: 10814
Deposited By: Mr Richard Ingham
Deposited On: 24 Jul 2008 14:16
Refereed?: Yes
Published?: Published
Last Modified: 18 Sep 2013 15:58
Identification Number:
URI: http://eprints.lancs.ac.uk/id/eprint/10814

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