, Volume 656, Issue 1, pp 5–14 | Cite as

Response of the floating aquatic fern Azolla filiculoides to elevated CO2, temperature, and phosphorus levels

  • Weiguo ChengEmail author
  • Hidemitsu Sakai
  • Miwa Matsushima
  • Kazuyuki Yagi
  • Toshihiro Hasegawa


Azolla filiculoides is a floating aquatic fern growing in tropical and temperate freshwater ecosystems. As A. filiculoides has symbiotic nitrogen-fixing cyanobacteria (Anabaena azollae) within its leaf cavities, it is cultivated in rice paddies to improve N availability and suppress other wetland weeds. To understand how C assimilation and N accumulation in A. filiculoides respond to elevated atmospheric carbon dioxide concentration (CO2) in combination with P addition and higher temperatures, we conducted pot experiments during the summer of 2007 and 2008. In 2007, we grew A. filiculoides in pots at two treatment levels of added P fertilizer and at two levels of [CO2] (380 ppm for ambient and 680 ppm for elevated [CO2]) in controlled-environment chambers. In 2008, we grew A. filiculoides in four controlled-environment chambers at two [CO2] levels and two temperature levels (34/26°C (day/night) and 29/21°C). We found that biomass and C assimilation by A. filiculoides were significantly increased by elevated [CO2], temperature, and P level (all P < 0.01), with a significant interaction between elevated [CO2] and added P (P < 0.01). Tissue N content was decreased by elevated [CO2] and increased by higher temperature and P level (all P < 0.01). The acetylene reduction assay showed that the N-fixation activity of A. filiculoides was not significantly different under ambient and elevated [CO2] but was significantly stimulated by P addition. N-fixation activity decreased at higher temperatures (34/26°C), indicating that 29/21°C was more suitable for A. azollae growth. Therefore, we conclude that the N accumulation potential of A. filiculoides under future climate warming depends primarily on the temperature change and P availability, and C assimilation should be increased by elevated [CO2].


Azolla filiculoides Carbon assimilation Elevated atmospheric carbon dioxide High temperature Nitrogen fixation Phosphorus nutrient 



This research was funded by a Grant-in-Aid for Scientific Research C (No. 19580019) from the Japan Society for the Promotion of Science. We thank Dr. Y. Kishida at Okayama University for providing A. filiculoides inocula.


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Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  • Weiguo Cheng
    • 1
    • 2
    Email author
  • Hidemitsu Sakai
    • 1
  • Miwa Matsushima
    • 3
  • Kazuyuki Yagi
    • 1
  • Toshihiro Hasegawa
    • 1
  1. 1.National Institute for Agro-Environmental SciencesTsukubaJapan
  2. 2.Faculty of AgricultureYamagata UniversityTsuruokaJapan
  3. 3.Faculty of HorticultureChiba UniversityMatsudoJapan

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