重金属汚染と樹木の生長 IV : 過剰Cu処理された当年生クロマツ苗の植物体内養分量および含水量

Abstract

過剰Cu処理された当年生クロマツ苗の植物体各部の養分濃度および含水量の経時変化を調べた。土壌に処理されたCuCl_2溶液の濃度は0, 40, 120, 260, 430ppmであった。結果の概要は, 1) 使用した土壌の置換態Cu濃度 (IN酢酸アンモニウムpH7. 0抽出) と希酸可溶態Cu濃度 (0. 1N塩酸抽出Cuから置換態Cuを差し引いたもの) はともに試験期間中に低下するが, 低下率は希酸可溶態が大きく, 両者の土壌中での形態的な変化は少ないようである。2) 植物体各部の含水量は6月から8月に大きく減少し, 8月以降も徐々に減少する。Cu処理により含水量は低下し, その傾向は, 6, 7月の根に最も明らかである。地上部の7, 8月の含水量は高濃度処理区で, 生育に危険な程度にまで低下した。3) 当年生クロマツ苗の養分濃度の季節変化はそれぞれの養分によって異なる。K, Mg, P, Feは生育期初期に高く, その後低下し安定する傾向がみられ, Pは生育期後半に再び濃度はいくらか上昇する。Caはこれらの養分と異なり生育期初期に低く, 後半に上昇する。植物体各部の養分濃度は一般に根の濃度が高く, 地上部では葉の濃度が高い。4) 植物体各部の養分濃度は過剰Cuによって低下する。その影響はCa, Pで最も明らかでFeではほとんどみられない。器官別には根および葉への影響が大きい。5) 土壌中の置換態K, Ca, Mg濃度はCu処理により低下し, Kに比べCa, Mgへの影響が大きい。

The effect of excessively applied Cu on mineral concentration and water content of one-year-old Japanese black pine (Pinus Thunbergii Parl.) was investigated. The concentrations of Cu (CuCl2) solution applied to the soils were 0, 40, 120, 260, 430 ppm respectively. The results are summarized as follows: 1) Cu concentrations of soils extracted by 0.1N HCl decrease more greatly than that exchanged by 1N CH3COONH4 (pH7.0) with the advance of seasons. It seems that forms of Cu in soils exchange little between Extra. Cu and Exch. Cu in the period of experiment. 2) Water content of plant is high in June and shows a tendency to decrease greatly in the early growing season, then the rate of decrease becomes slow from August to the late growing season. Water content of top in high concentration treatment decrease critically in July and August. 3) Mineral concentrations of plant parts of control group vary with the advance of the seasons respectively. The concentrations of K, Mg, P and Fe are high in the early growing season and after they show a tendency to decrease, they are stable in the late growing season, while P increases a little again. Contrary to these mineral, the concentration of Ca is low in June and increases with the course of time. The mineral concentration of root is the highest and that of leaf is higher than that of stem in top. 4) Mineral concentrations of plant parts decrease in high concentration treatments. The effect seems most evident on Ca and P but less on Fe. The effect of Cu on mineral concentration of root and leaf is evident. 5) The concentrations of exchangeable K, Ca and Mg in soils decrease with the increase of added Cu. The decreasing rates of Ca and Mg are greater than that of K.