重金属汚染と樹木の生長 V : 過剰Cu処理が当年生クロマツ, スギ, ヒノキ苗の生長と植物体内Cu濃度に及ぼす影響

Abstract

過剰Cu処理を行なった当年生クロマツ, スギ, ヒノキ苗の植物体内Cu濃度変化と, それらの樹種の生長への影響の違いについて考察した。Cuの土壌処理は, Cuとして0, 40, 175, 400ppmの濃度の塩化第二銅溶液をポットあたり1ℓ用いて行なった。結果の概要は次のとおりである。1) 土壌Cu濃度は経時的に減少し, かつその傾きは時間の経過とともに小さくなる傾向が認められた。2) Cu処理を施していない植物体の各器官のCu濃度は発芽直後高く, 以後低下する。当年生苗のCu濃度は葉の変動幅が大きく, 3樹種間ではヒノキの濃度が高かった。3) 過剰Cuの添加により, 根＞幹＞葉の順のCu濃度上昇の違いがみられ, 根においては発芽直後よりCu処理による影響は明らかであった。クロマツの根あるいは地上部への濃度の上昇はスギ, ヒノキに比べ遅れた。4) 当年生苗の生長に及ぼすCuの影響はスギ＞ヒノキ＞クロマツの順に現われた。

Difference of effect of excessive Cu on growth and Cu concentration of one-year-old seedlings among Kuromatsu (Pinus Thunbergii), Sugi (Cryptomeria japonica) and Hinoki (Chamaecyparis obtusa) was investigated. Cu applied to the soils was treated by one liter of copper (CuCl2) solution, whose concentration was 0, 40, 175, 400 ppm respectively. Treatment was carried out in Spring of examinating year and of preceding year. The results are summarized as follows; 1) Cu concentration of soils treated with excessively applied Cu decreased and the gradient of decrease became more gentle with the course of time. 2) Cu concentration of plant parts of control group changed greatly with the advance of season. They were high immediately after germination and showed a tendency to decrease. The fluctuaion of Cu concentration of leaf was wide and Cu concentration of one-year-old Hinoki seedlings was the highest in general among these three species. 3) The order of Cu concentration of plant parts treated excessive Cu was root>stem>leaf. Cu concentration of root increased from early growing season. The increase of Cu concentration of Kuromatsu seedlings was the slowest among these three species. 4) The order of the effect of excessive Cu on growth of one-year-old seedlings was Sugi>Hinoki>Kuromatsu among these three tree species.