Correlative X-ray Imaging to Reveal the Dissolution of Nanoparticles and Nutrient Transport in Plant Foliar Fertilization

Chengpeng Wu^1*Emil Visby Kristensen¹Francesco Minutello²Augusta Szameitat²Søren HUSTED²Rajmund Mokso^1*

• ¹Technical University of Denmark, Kongens Lyngby, Denmark
• ²Department of Plant and Environmental Sciences, Faculty of Natural and Life Sciences, University of Copenhagen, Frederiksberg, Capital Region of Denmark, Denmark

The integration of nanotechnology in agriculture allows for more precise nutrient delivery through nanoparticles (NPs), particularly via foliar application. To mature this technology for enhancing fertilizer efficiency, it is essential to shed new light on the transport and dissolution of NPs in plants. Available analytical methods struggle to address this challenge in a direct manner.We introduce correlative X-ray imaging as a novel analytical tool capable of tracking NP pathways, dissolution and hence nutrient release in plants. By utilizing three complementary X-ray techniques, we offer a unique insight into the plant processes associated with foliar fertilization. We demonstrate that small-angle X-ray scattering enables the characterization of NP size and concentration, while X-ray fluorescence imaging, maps the distribution of elements within the sample. Finally, micro-computed tomography integrates these findings into a complete three-dimensional digital representation of the plant's microstructure, revealing regions of apparent densification associated with NP accumulation.Using freeze-dried barley plants infiltrated with nano-hydroxyapatite (nHAP), we observed rapid dissolution of NPs, and we are able to associate time and space attributes to the translocation process of nutrients up to three days following foliar application of NPs. With the first pilot study of applying correlative X-ray imaging to live plants, we sought to indicate the potential of this new analytical approach for future nano-enabled agricultural research.