不同老化时间的TiO_2纳米颗粒对玉米生长的影响

为探讨老化时间对TiO_2纳米颗粒(nanoparticles,NPs)生物有效性的影响,研究了不同老化时间的Ti O_2NPs(0~120 d)对玉米幼苗生长的影响、在玉米体内的吸收及其在植株不同部位的存在位点等。研究发现,不同浓度的TiO_2NPs(1 000 mg·kg~(-1)和2 000 mg·kg~(-1))加入到土壤中,对玉米幼苗干鲜重没有明显的影响,但老化时间小于60 d时,对玉米幼苗株高有一定的抑制效应,老化60 d之后,随着老化时间的继续延长,毒性逐渐降低,最后趋于稳定。老化60 d时,TiO_2NPs处理的玉米幼苗根冠增大,玉米幼苗体内产生H2O_2的累积。在Ti O_2老化土壤中生长的玉米幼苗根系和地上部均有Ti的累积,1 000 mg·kg~(-1)的TiO_2NPs在玉米幼苗根部的生物累积系数达到35.4%,在地上部为13.6%,在玉米植株体内的转运系数为0.38;通过TEM观察,TiO_2NPs可以进入到玉米幼苗体内,并存在于根细胞的细胞质和叶绿体膜上,在叶片细胞的液泡和细胞核中也发现有TiO_2NPs的存在。上述研究结果为客观评价TiO_2NPs的生态风险提供了有用信息。

Effect of TiO2 Engineered Nanoparticles at Different Aging Times on the Growth of Zea mays L. in Soil

To investigate the effect of aging time on the biological effectiveness of TiO2 nanoparticles (NPs) in soil, the growth of maize seedlings, and the uptake and location of TiO2 NPs in maize seedlings in the TiO2 NPs treatment (1 000 mg?kg^-1 and 2 000 mg?kg^-1) with different aging times were studied. The results suggested that TiO2 NPs at all the tested aging times (0~120 d) had no negative effects on the dry or fresh weight of maize seedlings in soil. For the height of maize seedling, significant decrease was observed when the aging time of TiO2 NPs was less than 60 days. The inhibition on the height of maize seedling was decreased after aging over 60 d. After exposure to 60 d aged TiO2 NPs in soil, the root cap of maize seedling was increased and H2O2 was accumulated. Ti was detected in the roots and shoots of maize after TiO2 NPs exposure, indicating that TiO2 NPs could be taken up in maize seedlings, and then be transported from root to shoot. After exposure to 1 000 mg?kg^-1 TiO2 for 60 d, the bioaccumulation coefficient in maize seedling root was 35.4% and 13.6% in shoot. The transfer coefficient in maize seedlings was 0.38. As observed by TEM, TiO2 NPs could exist in chloroplast membrane and nucleus of root cells, and vacuoles and nucleus of leaf cells.