水培实验中不同粒径纳米TiO_2对芦苇种子发芽和植株生长和生理的影响

纳米二氧化钛(TiO_2-NPs)是目前应用最为广泛的纳米材料之一,进入到天然湿地和人工湿地中的TiO_2-NPs会在湿地生物、基质、水体之间进行迁移转化和归趋。目前针对TiO_2-NPs对湿地植物芦苇的毒性研究很少。本文采用水培实验方法,研究了不同粒径TiO_2对芦苇种子发芽和植株生长的影响,解析了TiO_2-NPs对芦苇的生态毒理效应。研究结果表明:几种粒径的TiO_2-NPs在较低浓度(≤200 mg·L~(-1))下对芦苇种子发芽均具有一定的促进作用,高浓度处理会抑制芦苇种子发芽;当TiO_2-NPs浓度为500 mg·L~(-1)时,处理后的芦苇种子的发芽指标较空白对照均出现显著降低,4 nm和20 nm的TiO_2-NPs对芦苇种子发芽的半数有效浓度(EC50)分别为1 075 mg·L~(-1)和1 680 mg·L~(-1)。TiO_2-NPs对芦苇植株的毒害作用表现为植株生长速度减缓甚至停滞、叶片失绿、植株萎焉或枯死、芦苇倒二叶面积增长率降低,并且TiO_2-NPs的粒径越小、浓度越高毒害作用越明显。随TiO_2-NPs浓度升高,处理后芦苇叶片的叶绿素含量和植株体内的Mg含量均降低,根系的超氧化物歧化酶(superoxide dismutase,SOD)活性、丙二醛(malondialdehyde,MDA)均升高,而且越小粒径的TiO_2-NPs对芦苇的处理效果越明显。3种粒径的TiO_2-NPs均能进入芦苇体内,粒径越小、浓度越高进入的量越多,但是TiO_2-NPs比较难以从根迁移转运至茎和叶。

Effect of Nano Titanium Dioxide with Different Particle Size on the Seed Germination and Plant Growth and Physiology of Phragmites australis in Hydroponic Experiments

Nano titanium dioxide (TiO2-NPs) is one of the most widely used nanometer materials,which will migrate and transform among the wetland biotas,substrate and water body as entering the natural wetland and constructed wetland.At present,there are few studies on the toxicity of TiO2-NPs to the Phragrnites australis.In this study,the effect of TiO2-NPs with different sizes on the seed germination and plant growth of typical constructed wetland plant-P,australis was explored through hydroponic experiments,and their ecotoxicological effects were also determined.The results showed that the seed germination of P.australis was promoted at low concentration (less than 200 mg·L-1) treatment by TiO2-NPs with different sizes,while was hindered at high concentration treatment.When the concentration of TiO2-NPs was higher than 500 mg-L-1,the seed germination indexes of treated P.australis significantly decreased in comparison with control samples.Moreover,the EC50 of 4 nm and 20 nm TiO2-NPs on the seed germination of P.australis were determined as 1 075 and 1 680 mg· L-1,respectively.The toxic effects of TiO2-NPs on P.australis were characterized as growth retardation and even stagnation,leaf chlorosis,plant wilting or death,and decrease in the area growth rate of second leaf from the top.Moreover,the decreased size and increased concentration of TiO2-NPs could strengthen the aforementioned toxic effects.With the increase of TiO2-NPs concentration,the chlorophyll in leaf and Mg content in plant of treated P australis decreased,while the superoxide dismutase (SOD) activity and malondialdehyde (MDA) content in the root system increased,and such treatment effect was more obvious as the smaller TiO2-NPs were used.TiO2-NPs with different sizes could enter the Paustralis,and small size or high concentration could favor this entrance.However,it was difficult for TiO2-NPs to transfer from roots to stems and leaves.