黑麦草对铀胁迫的光合响应及铀吸收特性研究

为探究铀污染土壤下黑麦草光合特性和体内各部位铀积累分布特征的变化,本研究通过盆栽土培试验,研究了不同外源铀浓度处理(0、25、50、75、100 mg·kg~(-1))下黑麦草光合气体交换变化参数、光合荧光参数和黑麦草对铀的富集特征的影响。结果显示,铀胁迫会使植物的光合速率(A)和气孔导度(Gs)显著降低(P0.05),光合性能指数(PIabs)随外源铀浓度的增加呈先增后减的趋势,但未对黑麦草的胞间CO_2浓度(Ci)、最大光化学效率(Fv/Fm)和相对可变荧光(Vj)产生显著影响。随外源铀污染浓度的增加,土壤中铀残留量、黑麦草体内地上部和地下部的累积量显著增加(P0.05),且随着生长时间的增加,土壤中铀残留量显著减小、黑麦草体内地上部和地下部的累积量显著增加。生物富集系数(BCF)和铀总提取量分别在100 mg·kg~(-1)处理下达到最大值。结果表明,黑麦草的光合荧光参数对铀具有较好的耐受性,而光合速率的降低可能是光抑制引起的,黑麦草对铀有较高的富集能力,且随着生长时间和外源处理浓度的增加而增加。

Photosynthetic response of ryegrass to uranium stress and the absorption characteristics of enriched uranium

In this study, we investigated the changes in the photosynthetic characteristics and the distribution of uranium in various parts of ryegrass grown in uranium-contaminated soil. Specifically, we determined changes in photosynthetic gas exchange and fluorescence parameters of ryegrass and uranium enrichment characteristics under different uranium concentrations. The results showed that uranium stress caused a significant decrease in photosynthetic rate and stomatal conductance of ryegrass plants; moreover, it promoted an initial increase and subsequent decrease in the photosynthetic performance index. However, it did not significantly affect the intercellular CO₂ concentration, the maximum photochemical efficiency, or the relative variable fluorescence of ryegrass leaves. Our results also revealed that the amount of uranium remaining in the soil and the accumulation of uranium in the above-and belowground parts of plants increased significantly with an increase in the content of exogenous uranium. With an increase in growing time, the amount of uranium remaining in the soil decreased significantly, whereas the cumulative amount of uranium in the above-and belowground plant parts increased significantly. Furthermore, the bioconcentration factor and total uranium extraction of ryegrass reached maximum levels at 100 mg·kg^-1. The photosynthetic fluorescence parameters of ryegrass indicate that ryegrass has a high tolerance to uranium as well as a high enrichment capacity for uranium, which increases with time and increasing exogenous uranium concentration.