Shabnam Nisha, Sharmila P, Pardha-Saradhi P
a Department of Environmental Studies , University of Delhi , Delhi , India.
b Department of Chemistry , Indian Institute of Technology , New Delhi , India.
Int J Phytoremediation. 2017 Jan 2;19(1):80-86. doi: 10.1080/15226514.2016.1216083.
Owing to wide range of applications, nanotechnology is growing expeditiously. Likely negative impact of nanoparticles (NPs), which are inevitably released into our surroundings, on living organisms is of growing concern. Findings presented here are outcome of investigations carried out to evaluate the impact of ionic and NP speciation states of silver on light harnessing photosynthetic events in Spirodela polyrhiza fronds. Fronds exposed to ionic speciation state showed significant decline in PS (photosystem) II efficiency (Fv/Fm; variable fluorescence/maximal fluorescence), while those exposed to silver nanoparticles (Ag-NPs) showed marginal decline. Accordingly, decline in amplitude of Chl a fluorescence transients was sharper in fronds treated with Ag than those treated with Ag-NPs. Of the various phases Chl a fluorescence transient, J-I phase [which reflects reduction of plastoquinone (PQ) pool] was most sensitive to both Ag and Ag-NPs. Phenomenological yield models, built using Biolyzer software, revealed that fronds exposed to Ag possessed significantly lower potential to trap and harness absorbed light energy for photochemical reactions than those exposed to Ag-NPs. Accordingly, dissipation of absorbed light energy as heat was significantly higher in fronds exposed to Ag than those exposed to Ag-NPs. These findings revealed that NP speciation state of silver is significantly less toxic to light harnessing photosynthetic machinery of S. polyrhiza, compared to ionic speciation state.
由于应用范围广泛，纳米技术正在迅速发展。不可避免地释放到我们周围环境中的纳米颗粒（NPs）对生物体可能产生的负面影响日益受到关注。此处呈现的研究结果是为评估银的离子和纳米颗粒形态对多根紫萍叶片光合捕光事件的影响而进行的调查结果。暴露于离子形态的叶片光合系统II效率（Fv/Fm；可变荧光/最大荧光）显著下降，而暴露于银纳米颗粒（Ag-NPs）的叶片则略有下降。因此，用银处理的叶片中叶绿素a荧光瞬变的振幅下降比用银纳米颗粒处理的叶片更明显。在叶绿素a荧光瞬变的各个阶段中，J-I阶段[反映质体醌（PQ）库的还原]对银和银纳米颗粒最为敏感。使用Biolyzer软件构建的现象学产量模型表明，与暴露于银纳米颗粒的叶片相比，暴露于银的叶片捕获和利用吸收的光能进行光化学反应的潜力显著更低。因此，暴露于银的叶片中作为热量耗散的吸收光能显著高于暴露于银纳米颗粒的叶片。这些发现表明，与离子形态相比，银的纳米颗粒形态对多根紫萍的光合捕光机制的毒性显著更低。
