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Inorganic carbon and pH dependency of Trichodesmium's photosynthetic rates.

Boatman, TG and Mangan, NM and Lawson, T and Geider, RJ (2018) 'Inorganic carbon and pH dependency of Trichodesmium's photosynthetic rates.' Journal of Experimental Botany, 69 (15). 3651 - 3660. ISSN 0022-0957

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Abstract

We established the relationship between photosynthetic carbon fixation rates and pH, CO2 and HCO3- concentrations in the diazotroph Trichodesmium erythraeum IMS101. Inorganic 14C-assimilation was measured in TRIS-buffered ASW medium where the absolute and relative concentrations of CO2, pH and HCO3- were manipulated. First, we varied the total dissolved inorganic carbon concentration (TIC) (< 0 to ~ 5 mM) at constant pH, so ratios of CO2 and HCO3- remained relatively constant. Second, we varied pH (~ 8.54 to 7.52) at constant TIC, so CO2 increased whilst HCO3- declined. We found that 14C-assimilation could be described by the same function of CO2 for both approaches but showed different dependencies on HCO3- when pH was varied at constant TIC than when TIC was varied at constant pH. A numerical model of Trichodesmium's CCM showed carboxylation rates are modulated by HCO3- and pH. The decrease in Ci assimilation at low CO2, when TIC was varied, is due to HCO3- uptake limitation of the carboxylation rate. Conversely, when pH was varied, Ci assimilation declined due to a high-pH mediated increase in HCO3- and CO2 leakage rates, potentially coupled to other processes (uncharacterised within the CCM model) that restrict Ci assimilation rates under high-pH conditions.

Item Type: Article
Uncontrolled Keywords: Trichodesmium, Cyanobacteria, Ocean acidification, CO2, Carbon acquisition, Gross photosynthesis, Net photosynthesis, Carbon concentrating mechanism (CCM)
Subjects: Q Science > QH Natural history > QH301 Biology
Divisions: Faculty of Science and Health > Life Sciences, School of
Depositing User: Elements
Date Deposited: 24 Apr 2018 15:04
Last Modified: 17 Sep 2019 14:15
URI: http://repository.essex.ac.uk/id/eprint/21885

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