Diurnal and seasonal variations in stomatal conductance of rice at elevated atmospheric CO2 under fully open-air conditions

Authors

  • HIROYUKI SHIMONO,

    Corresponding author
    1. Climate Change Research Team, National Agricultural Research Center for Tohoku Region, Shimokuriyagawa, Iwate, 020-0198, Japan;
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  • MASUMI OKADA,

    1. Climate Change Research Team, National Agricultural Research Center for Tohoku Region, Shimokuriyagawa, Iwate, 020-0198, Japan;
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  • MEGURU INOUE,

    1. Climate Change Research Team, National Agricultural Research Center for Tohoku Region, Shimokuriyagawa, Iwate, 020-0198, Japan;
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  • HIROFUMI NAKAMURA,

    1. Climate Change Research Team, National Agricultural Research Center for Tohoku Region, Shimokuriyagawa, Iwate, 020-0198, Japan;
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  • KAZUHIKO KOBAYASHI,

    1. Department of Global Agricultural Science, Graduate School of Agricultural and Life Science, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan and
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  • TOSHIHIRO HASEGAWA

    1. Agro-Meteorology Division, National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba, Ibaraki, 305-8604, Japan
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H. Shimono, Crop Science Laboratory, Faculty of Agriculture, Iwate University, 3-18-8, Ueda, Morioka, Iwate 020-8550, Japan. Fax: +81 19 621 6146; e-mail: shimn@iwate-u.ac.jp

ABSTRACT

Understanding of leaf stomatal responses to the atmospheric CO2 concentration, [CO2], is essential for accurate prediction of plant water use under future climates. However, limited information is available for the diurnal and seasonal changes in stomatal conductance (gs) under elevated [CO2]. We examined the factors responsible for variations in gs under elevated [CO2] with three rice cultivars grown in an open-field environment under flooded conditions during two growing seasons (a total of 2140 individual measurements). Conductance of all cultivars was generally higher in the morning and around noon than in the afternoon, and elevated [CO2] decreased gs by up to 64% over the 2 years (significantly on 26 out of 38 measurement days), with a mean gs decrease of 23%. We plotted the gs variations against three parameters from the Ball-Berry model and two revised versions of the model, and all parameters explained the gs variations well at each [CO2] in the morning and around noon (R2 > 0.68), but could not explain these variations in the afternoon (R2 < 0.33). The present results provide an important basis for modelling future water use in rice production.

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