Assessing plant uptake and transport mechanisms of engineered nanomaterials from soil
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Engineered nanomaterials: Production and uses
Uptake and translocation of ENMs by plants
Engineered nanomaterials (ENMs) are substances purposefully manufactured with dimensions in the nanoscale (10–9 m). Their small size, chemical composition, and structure give them distinct and sometimes unique properties (high-surfacearea-to-volume ratio, enhanced reactivity, optical and electrical properties, among others),1 which make them ideal for a wide variety of uses. Estimates indicate that silicon dioxide (SiO2) and titanium dioxide (TiO2) are the most produced ENMs worldwide, with production up to 95,000 and 88,000 metric tons/year, respectively. Iron oxides (FeOx), aluminum oxides (AlOx), and zinc oxide (ZnO) are also produced in large quantities, with amounts between 34,000 and 42,000 metric tons/ year, while production of cerium dioxide (CeO2) is estimated to be approximately 10,000 metric tons/year.2 The increasing production rates of these materials have raised concerns about environmental release of ENMs and its implications.3 Figure 1 shows the estimated global flow of ENMs in 2010, including (left) production (metric tons/year) and applications, and (right) destination and organisms that could be affected.
Predictions about the environmental accumulation of ENMs have motivated the scientific community to study their possible effects on soil-cultivated plants. Plants take up elements and other nutrients from the soil solution, but questions regarding root uptake and translocation of ENMs are still under investigation. Since 2008, several studies have reported the uptake and translocation of ENMs.4,5 Two research questions have been of particular interest. The first is whether uptake of ENMs was occurring, and second, whether the ENMs remained in the nanoform after traversing biological membranes. An overview of recent findings about the mechanisms of uptake and translocation of TiO2, CeO2, and ZnO ENMs is discussed here.
Plant uptake and transport of elements In order to understand the movement of elements within plants, we will refer to two processes—uptake, which is the root acquisition of elements from soil, and transport, or translocation of elements from roots to aboveground tissues (Figure 2).
Illya A. Medina-Velo, The University of Texas at El Paso, USA; [email protected] Jose R. Peralta-Videa, The University of Texas at El Paso, USA; [email protected] Jorge L. Gardea-Torresdey, Department of Chemistry, The University of Texas at El Paso, USA; [email protected] doi:10.1557/mrs.2017.87
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ASSESSING PLANT UPTAKE AND TRANSPORT MECHANISMS OF ENGINEERED NANOMATERIALS FROM SOIL
are carried across cell membranes by specific transporters (carriers and pumps) and moved through
