AOBPreview originally published online on October 24, 2008
Annals of Botany 2009 103(1):87-94; doi:10.1093/aob/mcn209
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Acclimation of nitrogen uptake capacity of rice to elevated atmospheric CO2 concentration
1 National Agricultural Research Center for Tohoku Region, Climate Change Laboratory, Shimokuriyagawa, Iwate, 020-0198, Japan
2 USDA-ARS, Crop Systems and Global Change Laboratory, Beltsville Agricultural Research Center, 10300 Baltimore Avenue, Beltsville, MD 20705-2350, USA
* For correspondence. Present address: Crop Science Laboratory, Faculty of Agriculture, Iwate University, 3-18-8, Ueda, Morioka, Iwate, 020-8550, Japan. E-mail shimn{at}iwate-u.ac.jp
Received: 9 July 2008 Returned for revision: 11 September 2008 Accepted: 18 September 2008 Published electronically: 24 October 2008
Background and Aims: Nitrogen (N) is a major factor affecting yield gain of crops under elevated atmospheric carbon dioxide concentrations [CO2]. It is well established that elevated [CO2] increases root mass, but there are inconsistent reports on the effects on N uptake capacity per root mass. In the present study, it was hypothesized that the responses of N uptake capacity would change with the duration of exposure to elevated [CO2].
Methods: The hypothesis was tested by measuring N uptake capacity in rice plants exposed to long-term and short-term [CO2] treatments at different growth stages in plants grown under non-limiting N conditions in hydroponic culture. Seasonal changes in photosynthesis rate and transpiration rate were also measured.
Key Results: In the long-term [CO2] study, leaf photosynthetic responses to intercellular CO2 concentration (Ci) were not affected by elevated [CO2] before the heading stage, but the initial slope in this response was decreased by elevated [CO2] at the grain-filling stage. Nitrate and ammonium uptake capacities per root dry weight were not affected by elevated [CO2] at panicle initiation, but thereafter they were reduced by elevated [CO2] by 31–41 % at the full heading and mid-ripening growth stages. In the short-term study (24 h exposures), elevated [CO2] enhanced nitrate and ammonium uptake capacities at the early vegetative growth stage, but elevated [CO2] decreased the uptake capacities at the mid-reproductive stage.
Conclusions: This study showed that N uptake capacity was downregulated under long-term exposure to elevated [CO2] and its response to elevated [CO2] varied greatly with growth stage.
Key words: Acclimation, elevated CO2, nitrogen uptake capacity, Oryza sativa, photosynthesis rate, rice, root development, transpiration rate
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