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CO2 and nitrogen, but not population density, alter the size and C/N ratio of Phytolacca americana seeds

  1. J.-S. HE1,2,*,
  2. D. F. B. FLYNN1,
  3. K. WOLFE-BELLIN2,
  4. J. FANG1,
  5. F. A. BAZZAZ2

Article first published online: 13 JUN 2005

DOI: 10.1111/j.1365-2435.2005.00981.x

Issue

Functional Ecology

Functional Ecology

Volume 19, Issue 3, pages 437–444, June 2005

Additional Information

How to Cite

HE, J.-S., FLYNN, D. F. B., WOLFE-BELLIN, K., FANG, J. and BAZZAZ, F. A. (2005), CO2 and nitrogen, but not population density, alter the size and C/N ratio of Phytolacca americana seeds. Functional Ecology, 19: 437–444. doi: 10.1111/j.1365-2435.2005.00981.x

Author Information

  1. 1

    Department of Ecology, College of Environmental Science, Peking University, Beijing 100871, China,

  2. 2

    Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA

* †Author to whom correspondence should be addressed. E-mail: jshe@pku.edu.cn

Publication History

  1. Issue published online: 24 JUN 2005
  2. Article first published online: 13 JUN 2005
  3. Received 25 May 2004; revised 5 November 2004; accepted 16 February 2005

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Keywords:

  • density;
  • elevated CO2;
  • McGinley–Charnov hypothesis;
  • resource allocation;
  • seed size

Summary

  • 1
    Plants can provision seeds by optimizing seed size, number and nutrient content to maximize parental fitness. According to the McGinley–Charnov hypothesis, seed size should be determined by the ratio of carbon to nitrogen (C/N) available to the plant, with larger seed size correlating with larger C/N ratios and smaller absolute N content.
  • 2
    This hypothesis was tested by establishing monocultures of Phytolacca americana L. (Phytolaccaceae) at three population densities under ambient and elevated CO2 environments, with two availabilities of soil N.
  • 3
    Elevated CO2 reduced both seed size and N concentration while increasing the C/N ratio; high soil N availability produced the opposite result for N concentration and C/N ratio. Higher planting densities reduced plant biomass, but did not alter seed size.
  • 4
    In accordance with the McGinley–Charnov hypothesis, larger seeds had both larger C/N ratios and smaller N content. However, the increase in C/N ratio caused by elevated CO2 corresponded with smaller seeds overall: elevated CO2 reduced seed size, although the seed size–C/N relationship remained positive.
  • 5
    These results suggest an alternative mechanism to explain variation in seed size, and suggest that future climate conditions may alter seed quality and plant reproductive behaviour.
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