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First published online October 1, 2004; 10.1104/pp.104.047936 Plant Physiology 136:3301-3312 (2004) © 2004 American Society of Plant Biologists Carbon Status Constrains Light Acclimation in the Cyanobacterium Synechococcus elongatus1Department of Biology, University of New Brunswick, Fredericton, New Brunswick, Canada E3B 6E1 (T.D.B.M., R.A.B., D.A.C.); and Department of Biology and Coastal Wetlands Institute, Mount Allison University, Sackville, New Brunswick, Canada E4L 1G7 (D.A.C.)
Acclimation to one environmental factor may constrain acclimation to another. Synechococcus elongatus (sp. PCC7942), growing under continuous light in high inorganic carbon (Ci; approximately 4 mM) and low-Ci (approximately 0.02 mM) media, achieve similar photosynthetic and growth rates under continuous low or high light. During acclimation from low to high light, however, high-Ci cells exploit the light increase by accelerating their growth rate, while low-Ci cells maintain the prelight shift growth rate for many hours, despite increased photosynthesis under the higher light. Under increased light, high-Ci cells reorganize their photosynthetic apparatus by shrinking the PSII pool and increasing Rubisco pool size, thus decreasing the photosynthetic source-to-sink ratio. Low-Ci cells also decrease their reductant source-to-sink ratio to a similar level as the high-Ci cells, but do so only by increasing their Rubisco pool. Low-Ci cells thus invest more photosynthetic reductant into maintaining their larger photosystem pool and increasing their Rubisco pool at the expense of population growth than do high-Ci cells. In nature, light varies widely over minutes to hours and is ultimately limited by daylength. Photosynthetic acclimation in S. elongatus occurs in both high and low Ci, but low-Ci cells require more time to achieve acclimation. Cells that can tolerate low Ci do so at the expense of slower photosynthetic acclimation. Such differences in rates of acclimation relative to rates of change in environmental parameters are important for predicting community productivity under variable environments.
1 This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) operating and equipment grants (to D.A.C.), NSERC postgraduate and University of New Brunswick Board of Governors scholarships (to T.D.B.M.), and the Mount Allison Coastal Wetlands Institute funded by the Canada Foundation for Innovation and Atlantic Canada Opportunities Agency. Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.104.047936. * Corresponding author; e-mail dcampbell{at}mta.ca; fax 5063642505. Received June 15, 2004; returned for revision July 29, 2004; accepted August 2, 2004. This article has been cited by other articles:
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