Effects of the water management in a rice field on leaf and panicle temperature under the high air temperature in summer

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K05851
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 41040:Agricultural environmental engineering and agricultural information engineering-related
• Research Institution: Ehime University
• Principal Investigator: Oue Hiroki 愛媛大学, 農学研究科, 教授 (80213627)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: イネの群落温度 / 気孔コンダクタンス / 夏季高温 / 水管理 / ひめの凜 / 光化学的応答 / 多層微気象モデル / 品種間差

Outline of Final Research Achievements

Comparisons of the measured stomatal conductance (gs) in rice cultivars Himenorin (HR), Nikomaru (NM), and others showed the gs of HR was highest. Comparisons of the measured canopy temperature (Tc) and panicle temperature (Tp) showed Tc and Tp were lowest in HR, which was regarded to be caused by the highest gs in HR that should have promoted transpiration to cool leaves and even surrounded panicles. Just after irrigation with cool water in a high temperature environment, the measured Tc decrease 0.4 to 0.7 °C, and Tc in HR was 0.5 to 0.8 °C lower than in NM. The numerical simulation with Multi-Layer Model showed that the calculated Tc under 28 °C water was 0.2 °C lower than under 32 °C water in both rice cultivars, and 0.4 °C lower in HR than in NM under both water temperature. The model simulation suggested that the mechanism of decreasing Tc and Tp was the lower upward long wave radiation and the lower sensible heat flux from the bottom canopy layer.

Free Research Field

地域水文気象学

Academic Significance and Societal Importance of the Research Achievements

暑さに強いとされる愛媛県オリジナルのイネ品種ひめの凜は，にこまるやコシヒカリよりも気孔コンダクタンス（gs）が高く葉温と穂温が低かったことから，高いgsが高温耐性の原因の一つと考えられた．この成果は，系統選抜中のイネ交配種のgsを比較するフェノタイピングで，高温耐性種を選択できる可能性を意味する．水管理の効果について，高温時の灌漑によるイネ群落温度の低下が測定によって実証された．また，多層モデルによるシミュレーションで，高温時の灌漑による低水温が，上向きの長波放射と顕熱フラックスを低下させ，群落上部の葉温と穂温を低下させる可能性が明らかになった．
以上が，本研究成果の学術的・社会的意義である．