2008 Joint Annual Meeting (5-9 Oct. 2008): Genotypic Variation of Yield Enhancement of Rice Cultivars with Different Maturity Group of Exposure to Free-Air CO2 Enrichment (FACE).
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534-17 Genotypic Variation of Yield Enhancement of Rice Cultivars with Different Maturity Group of Exposure to Free-Air CO2 Enrichment (FACE).



Monday, 6 October 2008
George R. Brown Convention Center, Exhibit Hall E
Hiroyuki Shimono1, Masumi Okada2, Yasuhiro Yamakawa2, Hirofumi Nakamura2, Kazuhiko Kobayashi3 and Toshihiro Hasegawa4, (1)Faculty of Agriculture, Iwate University, 3-18-8, Ueda, 020-8550, Morioka, Iwate, Japan
(2)National Agricultural Research Center for Tohoku Region, Shimokuriyagawa, 020-0198, Morioka, Iwate, Japan
(3)Dept. Global Agri Sci. U. of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan
(4)National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba, Ibaraki, 305-8604, Japan
Adequate N status in plants is a critical factor for ensuring their ability to respond positively to elevated atmospheric CO2 concentrations ([CO2]).  A cultivar with higher N concentration might thus respond better to elevated [CO2].  To test this hypothesis, we examined four rice cultivars with different times to maturity in a 2-year free-air CO2 enrichment (FACE) experiment.  Plant N concentration at the heading stage differed significantly between cultivars but without any significant [CO2] ´ cultivar interaction; cultivars that matured earlier had higher N concentrations.  Grain yield was significantly increased by elevated [CO2] (by up to 23%), but the magnitude differed among the cultivars due to a significant [CO2] ´ cultivar interaction; two cultivars (one with early and one with late maturity) responded more strongly to elevated [CO2] than those with intermediate maturity dates, resulting from increased spikelet density.  Biomass and N uptake at the heading stage were closely correlated with grain yield and spikelet density.  Our 2-year field trial rejected the N-response hypothesis and showed that the magnitude of the growth enhancement before heading rather than plant N concentration is a useful criterion for selecting cultivars capable of adapting to future elevated levels of [CO2].   
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