Inorganic carbon acquisition by Xiphophora chondrophylla (Phaeophyta, Fucales)

John A. Raven, John Beardall, Andrew M. Johnston, Janet E. Kübler, Shona G. Mcinroy

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Measurements of parameters related to photosynthesis, with particular reference to the mechanism of inorganic C acquisition, were made on Xiphophora chondrophylla (R. Brown ex Turner) Montagne ex Harvey, an Australasian fucoid living in the upper subtidal and in low intertidal rock pools. Photosynthesis as a function of incident photon flux density and external inorganic C concentration, capacity to use HCO3- , diel changes in titratable acidity of cell contents ('CAM-like' behaviour), rates of dark inorganic 14C fixation and the δ13C values of plant organic C were similar to values previously found for emersed and submersed specimens of the sympatric Hormosira banksii (Turner) Decaisne. This is consistent with the proposed close relationship of the genera Hormosira and Xiphophora and with earlier work showing the phyletic, as well as ecologically adaptive, importance of certain characteristics of inorganic C acquisition in the Fucaceae and related fucoids. The N content of Xiphophora chondrophylla was rather higher than that of Hormosira banksii (and its epiphyte Notheia anomala Harvey et Bailey, Fucales), so that the photosynthetic rate per unit tissue N was lower than that of these two algae and closer to that of some North Atlantic Fucaceae. Other things being equal, the photosynthetic characteristics of Xiphophora chondrophylla would make it even more prone to overgrowth by the epiphyte Notheia anomala than is the phorophyte Hormosira banksii.

Original languageEnglish
Pages (from-to)83-89
Number of pages7
Issue number2
Publication statusPublished - 1 Jan 1996

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