本年最後の水田勉強会。
根の表面から数㎜の空間を根圏という。根圏での根と微生物の相互作用の存在は良く知られてきたが、その実態については数年前まで殆ど不明のままだった。近年の遺伝解析技術の発展により、水稲の遺伝変異が何らかのシグナルにより根圏微生物叢の多様性を変化させること、その結果として土壌から水稲への養分供給ひいては水稲生育に影響している可能性が明らかに。水稲→根圏微生物→水稲というフィードバックループは、人→腸内細菌→人の関係を彷彿とさせる。
温暖化は微生物活性を増大させるため、長期的には土壌有機物を消耗して水稲生育を大きく阻害する懸念がある。それは、高温耐性品種により短期的な温暖化問題を克服したコメ生産に大きな警鐘を鳴らす。標高を積算温度の代理変数として捉え、標高低下に伴う温暖化が、水田土壌の微生物活性や有機物含量、水稲の収量や品質に与える影響を測定。非常に興味深い。
市川先生(教育学部)
「イネは、効率的な窒素利用のために、特定の土壌微生物を積極的に根圏に集めて利用する」
加藤ひなた(国際資源植物学)
「温暖化が水田土壌有機物と水稲生育に与える影響-標高を活用した実証調査―」
The Last Rice Field Study Meeting of the Year.
The rhizosphere refers to the space extending a few millimeters from the root surface. While the existence of root-microbe interactions in the rhizosphere has been well known, their actual mechanisms remained largely unknown until a few years ago. Recent advances in genetic analysis technology have revealed that rice genetic variations can alter rhizosphere microbial diversity through certain signals, which in turn may affect nutrient supply from soil to rice and ultimately rice growth. The feedback loop of rice → rhizosphere microbes → rice is reminiscent of the relationship between humans → gut bacteria → humans.
Global warming is expected to increase microbial activity, which may lead to long-term depletion of soil organic matter and significantly inhibit rice growth. This raises a major concern for rice production, which has overcome short-term warming problems through heat-tolerant varieties. Using elevation as a proxy variable for accumulated temperature, the study measures how warming associated with decreasing elevation affects microbial activity in paddy soils, organic matter content, and rice yield and quality. Very interesting.
Dr. Ichikawa (Faculty of Education)
“Rice plants actively recruit specific soil microorganisms to their rhizosphere for efficient nitrogen utilization”
Hinata Kato (Global Plant Resource Science)
“Effects of Global Warming on Paddy Soil Organic Matter and Rice Growth – An Empirical Survey Using Elevation -“
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