Carbon-concentrating mechanisms in seagrasses

Larkum, AWD; Davey, PA; Kuo, J; Ralph, PJ; Raven, JA

Carbon-concentrating mechanisms in seagrasses

Larkum, AWD

Davey, PA Kuo, J Ralph, PJ

Raven, JA

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Publication Type:: Journal Article
Citation:: Journal of Experimental Botany, 2017, 68 (14), pp. 3773 - 3784
Issue Date:: 2017-06-01

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Field	Value	Language
dc.contributor.author	Larkum, AWD https://orcid.org/0000-0002-0420-134X	en_US
dc.contributor.author	Davey, PA	en_US
dc.contributor.author	Kuo, J	en_US
dc.contributor.author	Ralph, PJ https://orcid.org/0000-0002-3103-7346	en_US
dc.contributor.author	Raven, JA https://orcid.org/0000-0002-2789-3297	en_US
dc.date.issued	2017-06-01	en_US
dc.identifier.citation	Journal of Experimental Botany, 2017, 68 (14), pp. 3773 - 3784	en_US
dc.identifier.issn	0022-0957	en_US
dc.identifier.uri	http://hdl.handle.net/10453/123625
dc.description.abstract	© The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. but that the case for concentration of CO2 at the site of Rubisco carboxylation is not proven. Seagrasses are unique angiosperms that carry out growth and reproduction submerged in seawater. They occur in at least three families of the Alismatales. All have chloroplasts mainly in the cells of the epidermis. Living in seawater, the supply of inorganic carbon (Ci) to the chloroplasts is diffusion limited, especially under unstirred conditions. Therefore, the supply of CO2 and bicarbonate across the diffusive boundary layer on the outer side of the epidermis is often a limiting factor. Here we discuss the evidence for mechanisms that enhance the uptake of Ci into the epidermal cells. Since bicarbonate is plentiful in seawater, a bicarbonate pump might be expected; however, the evidence for such a pump is not strongly supported. There is evidence for a carbonic anhydrase outside the outer plasmalemma. This, together with evidence for an outward proton pump, suggests the possibility that local acidification leads to enhanced concentrations of CO2 adjacent to the outer tangential epidermal walls, which enhances the uptake of CO2, and this could be followed by a carbon-concentrating mechanism (CCM) in the cytoplasm and/or chloroplasts. The lines of evidence for such an epidermal CCM are discussed, including evidence for special 'transfer cells' in some but not all seagrass leaves in the tangential inner walls of the epidermal cells. It is concluded that seagrasses have a CCM but that the case for concentration of CO2 at the site of Rubisco carboxylation is not proven.	en_US
dc.relation.ispartof	Journal of Experimental Botany	en_US
dc.relation.isbasedon	10.1093/jxb/erx206	en_US
dc.subject.classification	Plant Biology & Botany	en_US
dc.subject.mesh	Plant Epidermis	en_US
dc.subject.mesh	Carbon Compounds, Inorganic	en_US
dc.subject.mesh	Bicarbonates	en_US
dc.subject.mesh	Carbonic Anhydrases	en_US
dc.subject.mesh	Photosynthesis	en_US
dc.subject.mesh	Alismatales	en_US
dc.title	Carbon-concentrating mechanisms in seagrasses	en_US
dc.type	Journal Article
utslib.citation.volume	14	en_US
utslib.citation.volume	68	en_US
utslib.for	0607 Plant Biology	en_US
utslib.for	0703 Crop and Pasture Production	en_US
utslib.for	0604 Genetics	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Strength - C3 - Climate Change Cluster
pubs.organisational-group	/University of Technology Sydney/Students
utslib.copyright.status	closed_access
pubs.issue	14	en_US
pubs.publication-status	Published	en_US
pubs.volume	68	en_US

Abstract:

© The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. but that the case for concentration of CO2 at the site of Rubisco carboxylation is not proven. Seagrasses are unique angiosperms that carry out growth and reproduction submerged in seawater. They occur in at least three families of the Alismatales. All have chloroplasts mainly in the cells of the epidermis. Living in seawater, the supply of inorganic carbon (Ci) to the chloroplasts is diffusion limited, especially under unstirred conditions. Therefore, the supply of CO2 and bicarbonate across the diffusive boundary layer on the outer side of the epidermis is often a limiting factor. Here we discuss the evidence for mechanisms that enhance the uptake of Ci into the epidermal cells. Since bicarbonate is plentiful in seawater, a bicarbonate pump might be expected; however, the evidence for such a pump is not strongly supported. There is evidence for a carbonic anhydrase outside the outer plasmalemma. This, together with evidence for an outward proton pump, suggests the possibility that local acidification leads to enhanced concentrations of CO2 adjacent to the outer tangential epidermal walls, which enhances the uptake of CO2, and this could be followed by a carbon-concentrating mechanism (CCM) in the cytoplasm and/or chloroplasts. The lines of evidence for such an epidermal CCM are discussed, including evidence for special 'transfer cells' in some but not all seagrass leaves in the tangential inner walls of the epidermal cells. It is concluded that seagrasses have a CCM but that the case for concentration of CO2 at the site of Rubisco carboxylation is not proven.

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http://hdl.handle.net/10453/123625