重金属汚染と樹木の生長 III : 過剰Cu処理された当年生クロマツ苗の発芽, 伸長, 肥大生長に及ぼす影響

Abstract

過剰Cu処理された当年生クロマツ苗の発芽そしてその後の生育に及ぼす形態的な変化を調べた。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) 本実験の処理濃度範囲では発芽率自体への影響は少ないように思われるが, 発芽苗の土壌からの出現時期の遅れが認められる。2) 高濃度処理においては発芽後根の発達不良から転倒し枯死していく危険性をもつものが多い。3) 子葉, 胚軸といった種子のもつ栄養に生長が左右されるものへのCuの影響は比較的少ないが, その後形成される初生葉, 上胚軸さらに普通葉, 冬芽と形成時期の遅い器官程Cuの影響は明らかとなる。4) 根の伸長は過剰Cuにより抑制される。低濃度処理では生育期後半一時的に無処理苗より根の発達がすぐれる。5) Cuの影響は肥大生長より伸長生長は現われやすい。その結果形状比 (樹高/地際直径) は低下する。この傾向は低濃度処理 (処理3) でも生育初期より認められる。(Fig. 4)

The effect of excessively applied copper on development of one-year-old Japanese black pine (Pinus Thunbergii Parl.) in germination and succeeding stages was investigated. The concentration of copper (CuCl2) solution applied to the soils was 0, 40, 120, 260, 430 ppm. The results are summerized as follows: 1) It seems that the final germination percentage is little affected by copper in this range of concentration treated, though the time when seedling appears from soil in higher concentration is later than that in control and lower concentration. 2) Many seedlings treated with higher concentration fall down immediately after germination due to less developed root system. These seedlings are exposed to the danger of death by drying of roots. 3) The effect of Cu on development of cotyledon and hypocotyl which depend their nutrition on seed reserves seems less evident. But the development of juvenile leaf and epicotyl is apparently inhibited. That of foliage leaf and winter bud formed in the late growing season is also inhibited remarkably by copper treatment. 4) The development of root is checked greatly by excessive copper from the early stage of growth. But the elongation of root in lower concentration becomes more active temporarily during the late growing season than in control. 5) The more apparent effect of copper treatment on height growth is observed than that on diameter. Consequently the ratio of height to diameter (H/D) becomes decreasing and this tendency was very distinct early in growing season in even lower concentration treatment (Fig.4).