Planta

, Volume 188, Issue 1, pp 1–6

Role of external carbonic anhydrase in light-dependent alkalization byFucus serratus L. andLaminaria saccharina (L.) Lamour. (Phaeophyta)

  • Kurt Haglund
  • Ziyadin Ramazanov
  • Matern Mtolera
  • Marianne Pedersén
Article

DOI: 10.1007/BF01160705

Cite this article as:
Haglund, K., Ramazanov, Z., Mtolera, M. et al. Planta (1992) 188: 1. doi:10.1007/BF01160705

Abstract

It has been proposed that many marine macroalgae are able to utilize HCO3for photosynthesis and growth, and that energy-dependent ion pumping is involved in this process. We have therefore studied the light-dependent alkalization of the surrounding medium by two species of marine macroscopic brown algae,Fucus serratus L. andLaminaria saccharina (L.) Lamour. with the aim of investigating the role of extracellular carbonic anhydrase (EC 4.2.1.1.) in the assimilation of inorganic carbon from the seawater medium. In particular, the influence of membrane-impermeable or slowly permeable carbonic-anhydrase inhibitors on the rate of alkalization of the seawater has been investigated. Inhibition of the alkalization rate occurred in both species at an alkaline pH (pH 8.0) but no inhibition was observed at an acidic pH (pH 6.0). The alkalization was found to be light-dependent and inhibited by 3-(3′,4′-dichlorophenyl)-1, 1-dimethylurea and, thus, correlated with photosynthesis. Alkalization by macroalgae has previously been shown to be proportional to inorganiccarbon uptake. We suggest that alkalization of the medium at alkaline pH in both of the species examined is mainly the consequence of an extracellular reaction. The reaction is catalyzed by extracellular carbonic anhydrase which converts HCO3to OH and CO2; CO2 is then taken up through the plasmalemma. However, we do not exclude the involvement of other mechanisms of inorganic-carbon uptake.

Key words

AlkalizationCarbon assimilationCarbonic anhydraseFucusLaminariaMacroalgaePhotosynthesis

Abbreviations

AZ

acetazolamide

CA

carbonic anhydrase

CAext

extracellular carbonic anhydrase

Ci

inorganic carbon

DBS

dextran-bound sulfonamide

DCMU

3-(3′,4′-dichloro-phenyl)-1,1-dimethylurea

PPFD

photosynthetic photon flux density

Copyright information

© Springer-Verlag 1992

Authors and Affiliations

  • Kurt Haglund
    • 1
  • Ziyadin Ramazanov
    • 2
  • Matern Mtolera
    • 3
  • Marianne Pedersén
    • 1
  1. 1.Department of Physiological BotanyUppsala UniversityUppsalaSweden
  2. 2.Institute of Plant Physiology, Russian Academy of SciencesMoscowRussia
  3. 3.Institute of Marine SciencesUniversity of Dar es SalaamZanzibarTanzania
  4. 4.Department of BotanyLouisiana State UniversityBaton RougeUSA