Biotransformation in leaves of foliar applied ENMs

The effects of ENMs in plants have been described with respect to both, plant species and type of ENM. Studies performed in greenhouse facilities and research laboratories have shown positive and negative results on the photosynthetic mechanisms, which impact plant growth and enzymatic activities resulting in cytotoxicity. One mechanism of ENM uptake is via plant roots, which absorb ENMs from the water media in the soil and can be transported to the aboveground organs. However, uptake translocation can also occur in a reverse manner in cases where the plant is exposed to ENMs via foliar application. The pathways through the root system and through foliage vary greatly in mechanism. Different studies have concluded that plant exposure to ENMs affect both internal and external plant functions. Herein, we review the current scientific understanding of the application, uptake mechanisms, nutrient delivery, and biotransformation of foliar applied ENMs.