模拟土壤环境中聚乙烯微塑料的暴露对紫花地丁生理生态的影响

Effects of exposure to polyethylene microplastics in a simulated soil environment on the ecophysiology of Viola philippica

为了解土壤微塑料对野生植物生理生态的影响,以紫花地丁为材料,选用150μm聚乙烯微塑料(polyethylene microplastics,PE-MPs),分别设置对照组(CK)和不同暴露浓度,探究模拟土壤环境中微塑料污染对植物生理生态指标及其土壤理化指标的影响.结果表明,低浓度PE-MPs对紫花地丁产生的影响不显著,但高浓度会对植物的生理指标产生明显的抑制作用.PE-MPs暴露浓度超出500 mg/kg时,紫花地丁各项生理生态指标出现显著变化.在最高浓度为1500 mg/kg的暴露下,部分指标达最低.与CK相比,植物根系活力、叶绿素a、叶绿素b和总叶绿素分别显著降低55.2%、27.9%、23.3%和26.7%;抗氧化酶SOD、POD和CAT等酶活指标分别显著降低55.2%、35.1%和35.5%;植物叶绿素荧光参数F_(0)、F_(m)分别显著下降27.1%和17.8%.NPQ_Lss在暴露浓度为500 mg/kg下达到最低;1-Qp_Lss随PE-MPs暴露浓度增加呈上升趋势,在暴露浓度为1000 mg/kg条件下达最高.荧光成像结果表明,PE-MPs暴露浓度为1000或1500 mg/kg下,紫花地丁叶片活性显著降低.土壤pH和速效钾随PE-MPs暴露浓度增加呈上升趋势;有效磷和碱解氮含量则呈显著降低,有效磷在500 mg/kg暴露浓度下达最低,而碱解氮在1500 mg/kg暴露下达最低.此外,当PE-MPs暴露浓度高于500 mg/kg时,紫花地丁的各项生理指标受到显著抑制;同时,根系活力、叶绿素总量、SOD、F_(0)、F_(m)、1-Q_(p_Lss)、QY_(max)等多个指标与土壤碱解氮呈显著相关性.总体上,土壤环境中较低浓度(100 mg/kg以下)PE-MPs的暴露对紫花地丁的生理生态影响不显著;而较高浓度PE-MPs下紫花地丁的抗氧化酶系统与PSⅡ光合系统均受到显著破坏,耐受PE-MPs临界浓度约为100-500 mg/kg.

To explore the effects of soil microplastics on the physiology and ecology of wild plants,150μm polyethylene microplastics(PE-MPs)were used in this study.Control groups(CK)and different exposure groups were established to simulate the effects of MP pollution in the soil on plant physiological and ecological indicators and their soil physicochemical indicators,respectively.The results indicated that the effect of exposure to low concentrations of PE-MPs on Viola philippica was not significant enough;however,exposure to high concentrations had significant inhibition effects on plant physiological indices.When the exposure concentration of PE-MPs exceeded 500 mg/kg,significant changes were observed in the various physiological and ecological indices of Viola philippica.Some indicators reached their lowest values at the highest PE-MP concentration of 1500 mg/kg.Compared with the CK group,root activity,chlorophyll a,chlorophyll b,and total chlorophyll were significantly decreased by 55.2%,27.9%,23.3%,and 26.7%,respectively,at 1500mg/kg.Antioxidant enzyme activity indicators such as superoxide dismutase(SOD),peroxidase(POD),and catalase(CAT)were significantly reduced by 55.2%,35.1%,and 35.5%,respectively.Chlorophyll fluorescence parameters F_(0) and F_(m) were significantly decreased by 27.1%and 17.8%,respectively.Further,NPQ_(_Lss) reached its lowest level at 500 mg/kg;1-Q_(P_LSS) increased with increase in exposure concentrations of PE-MPs and reached its highest level at 1000 mg/kg.Fluorescence imaging results indicated that the leaf activity of Viola philippica significantly decreased at exposure concentrations of 1000 or 1500 mg/kg of PE-MPs.Fluorescence imaging indicated that the leaf activity of Viola philippica significantly reduced at 1000 or 1500 mg/kg.The soil pH value and fast-acting potassium increased with increase in exposure concentration of PE-MPs.However,the contents of effective phosphorus and alkaline nitrogen significantly decreased with exposure to the lowest effective phosphorus concentration of 500 mg/kg PE-MPs and lowest alkaline nitrogen at 1500 mg/kg.The study also indicated that various physiological indices of Viola philippica were significantly inhibited when the exposure concentration of PE-MPs exceeded 500 mg/kg.Meanwhile,several indicators,such as root vigor,total chlorophyll,SOD,F_(0),F_(m),1-Q_(P_LSS),and QY_(max),significantly correlated with soil alkaline dissolved nitrogen.Overall,the changes in physiological and ecological characteristics of V.philippica were not significant at lower concentrations of PE-MPs(below 100 mg/kg)in the soil environment,while the antioxidant enzyme system and PSII photosynthetic system of the plants were significantly disrupted at higher PE-MPs exposures,and their tolerable PE-MPs exposure ranged from about 100 to 500 mg/kg.