重金属汚染と樹木の生長 I : 過剰Cu処理された当年生クロマツ苗の光合成及び呼吸

Abstract

過剰Cu処理された当年生クロマツ苗の光合成, 及び呼吸速度を調べた。土壊に処理された溶液 (CuCl_2) の濃度は0, 40, 120, 260, 430ppmであった。その結果の概要は 1) 光合成速度は定数b, b/aで決定される P=bI/(1+aI), あるいは1/P=1/(bl)+a/bであらわされる。定数b, b/aは, 季節とともに変化するが, Cu処理濃度によっても異なる。2) 定数bは時間の経過とともにその値が小さくなる。このことは, 弱光域での光-光合成曲線の傾きが, 生育初期で高いことを示している。全期間を通じて, 高濃度処理と低濃度あるいは無処理のbの値はほとんどかわらないが, 中濃度処理のものは低い値を示すように思われる。(図5) 3) 定数b/aは一般に季節を追うに従って小さくなる傾向がみられる。光合成によるCO_2吸収は, 発芽直後最も高い。処理濃度が高くなれば, b/aの値は小さくなる。処理間の差は時とともによりはっきりしてくる。(図6) 4) 呼吸速度は発芽直後最も高い値を示す。すべての処理で, 呼吸速度は10月迄徐々に低下していくが, 11月はやや高い値を示す。高濃度処理区の呼吸速度は他の処理区のものより高い値を示す。5) 葉量そして葉の生長は図7に示すように処理間で明らかな差が認められる。

The photosynthetic and respiratory activities of one-year-old Japanese black pine(Pinus Thunbergii P.) seedlings treated with excessively applied copper (CuCl2) solution were investigated. The concentrations of copper solution applied to the soil were 0, 40, 120, 260, and 430 ppm. The results are summarized as follows: 1)The photosynthetic activity expressed as l/p=l/bI+a/b can be determined with the constants b and b/a. Both of the constants b and b/a change with the advance of the seasons and vary between the seedlings with different level of copper concentration treatments. 2)Constant b decreases with the course of time, which means the gradient of lightphotosynthetic curve in the lower light condition is greater in the early part of the season. In all seasons, the b values of high and low or non treated seedlings show little differences but that of medium treated seems to be less than the others(Fig. 5). 3)Constant b/a shows the general trend to decrease with the advance of season. The CO2 uptake due to photosynthetic activities is the highest in the measurements made just after germination. The higher the treatment concentration, the less the values of b/a become. The difference between the treatments becomes clearer with the course of time (Fig. 5). 4)The respiration rates are the highest in those measurements made just after germination. In all the treatments the respiration rates show the gentle downward trend until October, then abrupt increase in November. The respiration of the samples of high concentration treatments is higher than the others (Fig. 6). 5) The amount and the growth of the leaves vary remarkably between the treatments as illustrated in Fig. 7.