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ヒマシの根活動による根圏土壌中の溶存有機物およびCu画分の変動（英文
Variations of dissolved organic matter and Cu fractions in rhizosphere soil induced by the root activities of castor bean.
PMID: 32334255 DOI: 10.1016/j.chemosphere.2020.126800.
抄録
根の土壌相互作用は根圏における金属のバイオアベイラビリティーに影響を与え、植物による金属の取り込みと蓄積に影響を与える。本研究では、ヒマシ科植物を対象に、根袋法を用いた温室実験を行い、i)根圏がCuの分画に及ぼす影響、ii)根圏土壌中の溶存有機物(DOM)の特性を明らかにした。その結果、葉、茎、根のCu濃度は、対照ではそれぞれ15.41、6.71、47.85mgkgであり、Cu400処理ではそれぞれ96.5、254.9、3204mgkgに達した。ヒマシ科植物を培養した後の根圏土壌の酸交換性Cu濃度は、同じCu添加量ではバルク土壌よりも高いが、根圏土壌の還元性Cu濃度、酸化性Cu濃度、残留Cu濃度は、それぞれバルク土壌よりも低い値を示した。また、根圏土壌では、バルク土壌に比べてpHが低下し、全窒素濃度、全炭素濃度ともに上昇した。また、根圏土壌中の全低分子量有機酸（LMWOAs）及び全アミノ酸濃度は、Cu処理群では対照群に比べて、それぞれ15.18%から47.17%及び36.35%から200%の間で増加した。根圏土壌中のLMWOAs濃度が高い複雑でないDOMは、土壌Cuを相対的に安定な画分から利用可能な画分にシフトさせた。
The root soil interaction affects metal bioavailability in the rhizosphere, thus impacting the uptake and accumulation of metals by plants. In this study, a greenhouse experiment using a root-bag technique for castor bean plants was conducted to determine the i) rhizosphere effect on the fractions of Cu, and ii) the characteristics of dissolved organic matter (DOM) in the rhizosphere soil. Results showed that the Cu concentration in the leaves, stems, and roots was 15.41, 6.71, and 47.85 mg kg, respectively, in the control and reached up to 96.5, 254.9, and 3204 mg kg in Cu400 treatment, respectively. After cultivating castor bean plants, the concentration of acid exchangeable Cu in rhizosphere soil was higher than that in the bulk soil for the same Cu addition, whereas the concentrations of reducible Cu, oxidizable Cu, and residual Cu in the rhizosphere soil were all lower than those in the bulk soil, respectively. In comparison to the bulk soil, the pH decreased while the total nitrogen and total carbon concentrations both increased in the rhizosphere soil. Moreover, the concentrations of total low molecular weight organic acids (LMWOAs) and total amino acids in the rhizosphere soil of the Cu treatments increased by between 15.18% to 47.17% and 36.35%-200%, respectively with respect to the control. The less complex DOM with a high LMWOAs concentration in the rhizosphere soil shifted the soil Cu from a relative stable fraction to available fractions.
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