As a broad spectrum antibiotic, silver nanoparticles (AgNPs) are widely used in numerous commercial products, such as medical equipments and antibacterial or deodorant products.They are inevitably discharged into the environments in the process of their production, transportation, consumption and disposition.  

Aquatic systems are believed to be one of the pools of waste AgNPs. The discharged AgNPs aggravate the changes of structure and loss of function of aquatic systems because of pollution and eutrophication. 

JIANG Hongsheng, a Ph.D. student from Wuhan Botanical Garden, supervised by Prof. LI Wei and Prof. YIN Liyan, investigated the effects of AgNPs to macrophyte. He used chlorophyll fluorescence and enzymology techniques to determine the mechanism of AgNPs toxicity to an aquatic plant Spirodela polyrhiza. 

The first step of CO₂ assimilation in the Calvin–Benson cycle, ribulose-1, 5-bisphosphate carboxylase–oxygenase (Rubisco) was very sensitive to AgNPs. The decrease of Rubisco activity with increasing AgNPs concentrations might result in a decrease of solar energy utilization. 

As a consequence, the accumulated electrons can generate additional reactive oxygen species (ROS) within the chloroplast disturbed the whole energy transfer reactions in duckweed photosynthesis. 

This research was supported by the National Natural Science Foundation of China, and the National Key Basic Research and Development Program.  

Relevant results entitled “Silver nanoparticles induced reactive oxygen species via photosynthetic energy transport imbalance in an aquatic plant” were published in Nanotoxicology. 

Schematic diagram depicting ROS induced by AgNPs in the process of photosynthesis (Image by JIANG Hongsheng)