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Diel shifts in carboxylation pathway and metabolite dynamics in the CAM bromeliad Aechmea 'Maya' in response to elevated CO2

Lookup NU author(s): Dr Johan Ceusters, Professor Anne Borland

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Abstract

• Background and Aims: The deployment of temporally separated carboxylation pathways for net CO2 uptake in CAM plants provides plasticity and thus uncertainty on how species with this photosynthetic pathway will respond to life in a higher-CO2 world. The present study examined how long-term exposure to elevated CO2 influences the relative contributions that C3 and C4 carboxylation make to net carbon gain and to establish how this impacts on the availability of carbohydrates for export and growth and on water use efficiency over the day/night cycle. • Methods: Integrated measurements of leaf gas exchange and diel metabolite dynamics (e.g. malate, soluble sugars, starch) were made in leaves of the CAM bromeliad Aechmea 'Maya' after exposure to 700 μmol mol-1 CO2 for 5 months. • Key Results: There was a 60% increase in 24-h carbon gain under elevated CO2 due to a stimulation of daytime C3 and C4 carboxylation in phases II and IV where water use efficiency was comparable with that measured at night. The extra CO2 taken up under elevated CO2 was largely accumulated as hexose sugars during phase IV and net daytime export of carbohydrate was abolished. Under elevated CO2 there was no stimulation of dark carboxylation and nocturnal export and respiration appeared to be the stronger sinks for carbohydrate. • Conclusions: Despite the increased size of the soluble sugar storage pool under elevated CO2, there was no change in the net allocation of carbohydrates between provision of substrates for CAM and export/respiration in A. 'Maya'. The data imply the existence of discrete pools of carbohydrate that provide substrate for CAM or sugars for export/respiration. The 2-fold increase in water-use efficiency could be a major physiological advantage to growth under elevated CO2 in this CAM bromeliad. © The Author 2008. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved.


Publication metadata

Author(s): Ceusters J, Borland AM, Londers E, Verdoodt V, Godts C, De Proft MP

Publication type: Article

Publication status: Published

Journal: Annals of Botany

Year: 2008

Volume: 102

Issue: 3

Pages: 389-397

Print publication date: 01/09/2008

ISSN (print): 0305-7364

ISSN (electronic): 1095-8290

Publisher: Oxford University Press

URL: http://dx.doi.org/10.1093/aob/mcn105

DOI: 10.1093/aob/mcn105


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