Growth, photosynthesis and carbon metabolism in the temperate marine diatomSkeletonema costatumadapted to low temperature and low photon-flux density
✍ Scribed by A. Mortain-Bertrand; C. Descolas-Gros; H. Jupin
- Book ID
- 104753345
- Publisher
- Springer-Verlag
- Year
- 1988
- Tongue
- English
- Weight
- 735 KB
- Volume
- 100
- Category
- Article
- ISSN
- 0025-3162
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✦ Synopsis
The temperate diatom Skeletonema costatum (Grev.) Cleve was grown in low temperature and/or low light conditions. The cultures were acclimatized for at least three months before experiments were begun. Our data indicate that the initial slope of the photosynthesis vs irradiance curve (c 0 is controlled predominantly by light history and the lightsaturated photosynthesis (Pma0 by temperature. The number of divisions per day decreased with decreasing light intensity, but was identical for cultures grown at 3 ~ or 18 ~ The metabolic pathways of inorganic carbon fixation were not fundamentally affected by low temperature or low light intensity, but both these factors increased labelling of C 3 compounds, synthesized by the Calvin-Benson cycle, and decreased that of phosphoenolpyruvate (PEP) and other metabolites. This indicates an enhancement of ribulose-l,5bisphosphate (RuBP) carboxylase activity, which is the first step in the C 3 pathway (3-phosphoglycerate and sugar phosphate synthesis); this may optimize cell functions. At low temperatures, a seven-fold increase in RuBP carboxylase activity per cell was observed. S. costatum is able to adapt to low irradiance by increasing c~ and decreasing I k (the ratio of Pm,x : c~, light intensity at onset of light saturation), and to low temperature by increasing its cellular chlorophyll a and RuBP carboxylase content. However, in the latter case, adaptation is not optimal. This study revealed two main features: (1) there is evidence that RuBP carboxylase has a key function in adjustment to high rates of photosynthesis at suboptimal temperatures or irradiances; (2) adaptive mechanisms are dynamic processes and the role of the time scale in physiological adaptation should be considered.