Thermal acclimation and photoacclimation of photosynthesis in the brown alga Laminaria saccharina

Authors

  • K. M. MACHALEK,

    1. Department of Plant Biology and Center for Marine Studies, 5722 Deering Hall, University of Maine, Orono, ME 04469-5722, USA
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    • *

      Marine Science Institute, University of Texas at Austin, 750 Channelview Drive, Port Aransas, Texas

  • I. R. DAVISON,

    Corresponding author
    1. Department of Plant Biology and Center for Marine Studies, 5722 Deering Hall, University of Maine, Orono, ME 04469-5722, USA
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  • P. G. FALKOWSKI

    1. Oceanographic and Atmospheric Sciences Division, Brookhaven National Lab, Upton, Long Island, NY 11973, USA
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Ian R. Davison, Department of Plant Biology and Center for Marine Studies, 5722 Deering Hall, University of Maine, Orono, ME 04469-5722, USA.

ABSTRACT

Thermal acclimation and photoacclimation of photosynthesis were compared in Laminaria saccharina sporophytes grown at temperatures of 5 and 17 °C and irradiances of 15 and 150μmol photons m−2 s−1. When measured at a standard temperature (17°C), rates of light-saturated photosynthesis (Pmax) were higher in 5 °C-grown algae (c. 3.0 μmol O2 m−2 s−1) than in 17 °C-grown algae (c. 0.9 μmol O2 m-2 s-1). Concentrations of Rubisco were also 3-fold higher (per unit protein) in 5 °C-grown algae than in algae grown at 17 °C. Light-limited photosynthesis responded similarly to high temperature and low light Photon yields (α) were higher in algae grown at high temperature (regardless of light), and at 5 °C in low light, than in algae grown at 5 °C in high light Differences in a were correlated with light absorption; both groups of 17 °C algae and 5 °C low-light algae absorbed c. 75% of incident light, whereas 5 °C high-light algae absorbed c. 55%. Increased absorption was correlated with increases in pigment content PSII reaction centre densities and the fucoxanthin-Chl ale protein complex (FCP). Changes in a were also attributed, in part, to changes in the maximum photon yield of photosynthesis (0max). PSI reaction centre densities were unaffected by growth temperature, but the areal concentration of PSI in low-light-grown algae was twice that of high-light-grown algae (c. 160.0 versus 80.0 nmol m−2). We suggest that complex metabolic regulation allows L, saccharina to optimize photosynthesis over the wide range of temperatures and light levels encountered in nature.

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