The environmental effects of engineered nanoparticles have recently been investigated. This review found that the interaction between plants and nanoparticles is very complex. Some nanoparticles are beneficial to plants while others are harmful. Still others have apparently no effect. However, these observations are made on a gross scale. The impact of stored nanoparticles on other members of the food chain like animals, and ultimately on humans, is a matter of great concern. At present, no definitive conclusions can be made based on the research published so far.
Environmental conditions may influence plant contents. The absorption of certain chemicals by plants can reach toxic levels. The toxic elements can then get into the food chain via plant products and pose a health hazard. Plants have evolved and survived in the presence of natural nanoparticles. However, the effect of engineered nanoparticles (ENP) on plants has not been studied. This review gathered information from different studies published on absorption, translocation, accumulation, and biotransformation of metal based (MB) and carbon based (CB) ENP in edible plants. These processes depend upon several factors like plant species, the size, type, chemical composition, stability of the ENP, and the environment. Soil, sludge, sediments, and natural organic matter (NOM) from dead animals and plants change the interaction between plants and nanoparticles. This field of nanoecotoxicology is a new and emerging field of research. The current review studied various evidences about plant-nanoparticle interaction and reviewed the potential benefits and risks to the plants.
The review of the research articles published in the emerging domain of nanoparticle toxicity was studied. This review studied two types of nanoparticles. The first type of nanoparticles was MB, for example, TiO2, CeO2, Fe3O4, and ZnO. The other was CB, for example, fullerene C70 also known as fullerol. This review also studied nanomaterials from silver, copper, and iron. It was observed how these particles get into plants (absorption), how they are stored in the plants (bioaccumulation), and how they can be harmful (cellular and DNA damage). Finally, this review attempted to draw a conclusion based on the present state of research being conducted in this field.
- Some nanoparticles do not have any effect on the plant physiology. For example, zero-valent iron had no effect on germination of flax, red clover, white clover, barley, and rye grass. Similarly, aluminum had no effect on the germination of radish, rape, lettuce, corn, and cucumber and did not show toxicity in red kidney beans and rye grass.
- Some nanoparticles were beneficial to plant growth. Rutile (TiO2) increased the germination, germination index and vigor index, plant dry weight, chlorophyll formation, and photosynthetic rate in spinach. A mixture of gold and copper (Au/Cu) improved the shoot to root ratio in lettuce.
- Some studies found that nanoparticles are toxic to plant cell and damage the genetic material. For example, TiO2 nanoparticles less than 100 nm in size were found to be genotoxic as well as cytotoxic in certain plants. Zinc (Zn) used as an aqueous suspension highly reduced the root growth of radish, rape, ryegrass, lettuce, corn, and cucumber.
- However, some nanoparticles had varying effects on different plant species. Carbon nanotubules had no effect on the growth of cabbage, carrot, and lettuce but delayed the flowering and decreased the yield of rice and reduced the biomass by 38% in zucchini.
The authors agree that in case of nanoparticles such as C70, Fe3O4, and TiO2, biotransformation was not observed. They confirm that nanoparticles can undergo biotransformation and can accumulate in plants. However, the authors suggest that there are limited studies in this field and much research work is required to be conducted on the mechanism of biotransformation, transmission of nanoparticles to the plant’s next generation, and transfer of nanoparticles in the food chain.
The current review investigates the ecological toxicity of nanoparticles. Plants have been exposed to natural nanoparticles in the environment for thousands of years. The nanoparticles from metal and carbon pose a new threat. The interaction of plants with such nanoparticles can be beneficial to some plants and harmful to others. The exact mechanisms of interaction have also not been explained fully. For example, it is thought that nanoparticles clog the root openings and affect water conduction and nutrient uptake in roots. It is found that solvents may also affect the toxicity of the nanoparticles. It is not clear whether genetic damage and cellular toxicity of certain nanoparticles are due to the particles themselves or changes in their structures after absorption by the plants. Thus, there are no conclusive practical recommendations that can be drawn about nanotoxicity based on the present state of the research. Further research is certainly needed, as the effects of nanomaterials on plants and animals are becoming a growing concern.
For More Information:
Interaction of Nanoparticles with Edible Plants and Their Possible Implications in the Food Chain
Publication Journal: Journal of Agricultural and Food Chemistry, March 2011
By Cyren Rico; Sanghamitra Majumdar
From the University of Texas at El Paso, El Paso, Texas
*FYI Living Lab Reports Are Summaries of the Original Research.