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Cited by 92Photosynthetic Processes and MechanismsMarine and coastal plant biologyMarine and coastal ecosystems

Alternative Methods of Photosynthetic Carbon Assimilation in Marine Macroalgae

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Reiskind, Julia B., Seamon, Paula T., Bowes, George·1988·Plant Physiology
DOI 10.1104/pp.87.3.686PMC PMC1054821
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Abstract

Two green macroalgae, Codium decorticatum and Udotea flabellum, differ photosynthetically. Codium had high O(2)-sensitive, and Udotea low O(2)-insensitive, CO(2) compensation points; Codium showed a Warburg effect at seawater dissolved inorganic carbon levels and had photorespiratory CO(2) release, whereas Udotea did not. Seawater dissolved inorganic carbon levels did not saturate photosynthesis. For Codium, but not Udotea, the Warburg effect was increased by ethoxyzolamide, a carbonic anhydrase inhibitor, at high but not low pH. Isolated chloroplasts from both macroalgae showed a Warburg effect that was ethoxyzolamide-insensitive. In both macroalgae, chloroplastic and extrachloroplastic carbonic anhydrase activity was present. P-enolpyruvate carboxykinase (PEPCK) carboxylating activity in Udotea extracts was equivalent to that of ribulose bisphosphate carboxylase, and enzyme activities for C(4) acid metabolism and P-enolpyruvate regeneration were sufficient to operate a limited C(4)-like system. In Udotea, malate and aspartate were early-labeled photosynthetic products that turned over within 60 seconds. Photorespiratory compounds were much less labeled in Udotea. Low dark fixation rates ruled out Crassulacean acid metabolism. A limited C(4)-like system, based on PEPCK, is hypothesized to be the mechanism reducing photorespiration in Udotea. Codium showed no evidence of photosynthetic C(4) acid metabolism. Marine macroalgae, like terrestrial angiosperms, seem to have diverse photosynthetic modes.

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  • C3 plants may benefit from increased CO2 concentrations because RuBisCO is not substrate-saturated at current CO2 levels.

    “C3 plants that utilize RuBisCO as their initial carboxylating enzyme experience loss of fixed carbon due to photorespiration and may benefit from increased CO2 concentrations since RuBisCO is not substrate-saturated at current CO2 levels [1, 7].”

    From Ocean Acidification Accelerates the Growth of Two Bloom-Forming Macroalgae (2016) · cites this paper as [7]

    The Discussion (page unavailable) reports that Codium behaves like a C3 system and that increasing dissolved inorganic carbon reduces its photorespiration. The paper also says seawater carbon levels do not saturate photosynthesis, but it does not establish that RuBisCO is unsaturated at current CO2 levels in C3 plants generally. (LLM, conf=0.82)

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  • C4 plants may not benefit from increased CO2 because PEPC is substrate-saturated at current CO2 levels.

    “C4 plants that utilize phosphenolpyruvate carboxylase (PEPC) experience little photorespiratory loss due to use of carbon concentrating mechanisms (CCM) and thus may not benefit from increased CO2 since PEPC is substrate-saturated at current CO2 levels [1, 7].”

    From Ocean Acidification Accelerates the Growth of Two Bloom-Forming Macroalgae (2016) · cites this paper as [7]

    The Abstract identifies PEPC as an enzyme found in terrestrial C4 plants. However, the paper reports reduced photorespiration in the marine alga Udotea through PEPCK, not PEPC, and does not say that PEPC is saturated at current CO2 levels or that C4 plants would gain little from increased CO2. (LLM, conf=0.78)

    Experimental — accuracy not yet measured

  • C3 algae can benefit from high CO2 because their RuBisCO is not substrate-saturated at current CO2 levels (~400 ppm).

    “C3 algae can benefit from high CO2 as their RuBisCO is not substrate-saturated at current CO2 levels (~400ppm) [7, 43].”

    From Ocean Acidification Accelerates the Growth of Two Bloom-Forming Macroalgae (2016) · cites this paper as [7]

    The Results (page not given) report that photosynthesis in Codium, which the Discussion describes as C3-like, was not fully saturated at usual seawater dissolved inorganic carbon levels; higher levels partially relieved oxygen inhibition. This supports a potential benefit from more available carbon, but the paper does not establish that RuBisCO itself is substrate-unsaturated at approximately 400 ppm CO2. (LLM, conf=0.86)

    Experimental — accuracy not yet measured

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Research works printed but not linked: 1

  1. [12]12. EDWARDS GE, SC HUBER 1981 The C4 pathway. In MD Hatch, NK Boardman, eds, The Biochemistry of Plants. A Comprehensive Treatise. Vol 8 Photo- synthesis. Academic Press, New York, pp 237-281

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Authors
Reiskind, J. B., Seamon, P. T., & Bowes, G.
Affiliations
University of Florida (US)
Venue
Plant Physiology
Publisher
Oxford University Press (OUP)
Published
1988-07-01
Volume
87
Issue
3
Pages
686-692
ISSN
  • 0032-0889 (ISSN-L)
  • 1532-2548
DOI
10.1104/pp.87.3.686
PMC
PMC1054821
OpenAlex
W2088991522
Cited by
92
References
25
Citations by year
2026: 1 · 2024: 2 · 2023: 1 · 2022: 6 · 2021: 5 · 2020: 3 · 2019: 1 · 2018: 1 · 2017: 1 · 2016: 7 · 2015: 1 · 2014: 6 · 2013: 5 · 2012: 3
FWCI
1.85
Type
journal article
Language
en
Open access
Licence
aspb.org/publications/aspb-journals/open-articles (vor, 365 d)
Locations
  • PLANT PHYSIOLOGY (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • U.S. Department of Agriculture
  • Bundesinstitut für Sportwissenschaft
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Photosynthetic Processes and Mechanisms
  • Physical Sciences › Earth and Planetary Sciences › Oceanography › Marine and coastal plant biology
  • Physical Sciences › Earth and Planetary Sciences › Oceanography › Marine and coastal ecosystems
Keywords
photosynthetic carbon assimilation, seaweed, Codium decorticatum, Warburg effect, photorespiration, carbonic anhydrase, ethoxyzolamide, phosphoenolpyruvate carboxylase, CAM photosynthesis, CO2 compensation point, dissolved inorganic carbon, chloroplasts, malate, aspartic acid, dark respiration

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