铀污染环境下植物的光合生理变化及对铀的吸收转移

Photosynthetic physiological changes and the uranium accumulation of plants in the uranium contaminated environment

在25 mg/kg、75 mg/kg、125 mg/kg、175 mg/kg铀（乙酸双氧铀）污染土壤的盆栽试验中，通过光合气体交换参数和叶绿素荧光参数研究了铀对向日葵（ Helianthus annuus ）、四季豆（ Phaseolus vulgaris ）、红圆叶苋（ Iresine herbstii ）、四季牛皮菜（ Beta vulgaris L.）和大叶菠菜（ Spinacia oleracea ）5种植物光合生理的影响。结果表明：1）在不同质量比铀处理下，植物光合生理变化较大。四季豆的净光合速率（ P n ）是对照（CK）的35.2%-87.0%，大叶菠菜是CK的147.4%-178.1%，红圆叶苋是CK的112.3%-133.5%，向日葵是CK的98.2%-115.6%，四季牛皮菜是CK的94.7%-108.4%；铀污染使植物的初始荧光（ F o ）均降低，最大光化学量子产量（ F v / F m ）增加0.3%-3.7%，但在铀质量比为125 mg/kg和175 mg/kg时，红圆叶苋的 F v / F m 略有下降，为对照的99.3%和98.0%，整体影响不明显。2）茎叶铀质量比以四季豆和大叶菠菜较高，根系铀质量比以四季豆和向日葵较高，整株铀质量比较高的依次是四季豆、大叶菠菜和向日葵。但试验植物地上器官铀质量比均小于根系铀质量比，植株铀质量比小于土壤铀污染量，说明这5种植物的铀转移能力较低。3）四季豆光合系统抗铀胁迫能力较弱，但根系铀质量比是土壤铀污染量的1.55-2.45倍，可以作为固持修复植物。

This paper takes it as the aim of its study to disclose the photosynthetic physiological changes, the absorption and transference of the uranium by the plants in the uranium contaminated environment. For this purpose, we have investigated the photosynthetic physiological changes of plants growing in the uranium （U） contaminated soil by the photosynthetic gas exchange parameters and chlorophyll fluorescence parameters through a pot experiment. In the experimental process, we have observed and found the effects of the uranium on the photosynthetic physiological changes of such plants as Helianthus annuus , Phaseolus vulgaris , Iresine herbstii , Beta vulgaris L. and Spinacia oleracea . The contaminated soils in which the said plants are growing contain 25 mg/kg, 75 mg/kg, 125 mg/kg and 175 mg/kg U （UO 2 （CH 3 COO） 2 ·2H 2 O） respectively. The results of our experiments show that： （1） Great changes have been brought about to the plant＇s growth through photosynthetic physiological function under different concentrations of uranium contamination. The contrast percentage ratios of the net photosynthetic rate （ P n ） of Phaseolus vulgaris , Spinacia oleracea , Iresine herbstii , Helianthus annuus , Beta vulgaris L. between the experimental group and the control group （CK） can be illustrated as： 35.2%-87.0%, 147.4%-178.1%, 147.4% 178.1%, 98.2%-115.6%, 94.7%-108.4%, respectively. The minimum fluorescence （ F o ） of the 5 plants grown in our pot experiment has all been found decreased, whereas most of their maximum photochemical efficiency （ F v / F m ） has been found 0.3% to 3.7 %, much greater than CK. But the percentage ratio of F v / F m is 99.3% to 98.0% of CK in Iresine herbstii grown in the soil with the content of U being 125 mg/kg and 175 mg/kg. However, the overall impact remains minute. （2） The uranium content in the aboveground organs of Phaseolus vulgaris and Spinacia oleracea has been found a bit higher and a higher uranium content exists in the roots of Phaseolus vulgaris and Helianthus annuus . The whole plants have a higher uranium content according to the descending order of Phaseolus vulgaris 〉 Spinacia oleracea 〉 Helianthus annuus . But the uranium content in aboveground organs of the plants under the experiment are less than that of uranium content in the roots. Thus, the uranium content in the plants is less than that in the contaminated soils. Thus, it can be seen that the uranium transfer capacities of the 5 kinds of plant are all minute. （3） The uranium stress resistance of Phaseolus vulgaris proves to be weak in the photosynthetical system, but the uranium content in the roots proves to be 1.55-2.45 times as much as that in the uranium contaminated soils, which can be used as a kind of immobilized remediation for the plant.