3D X-ray Microscopy Lights up Nanoparticles in Plants

The discovery of new plant fertilization strategies heavily relies on our capabilities to probe physiological processes in living plants with subcellular precision. State-of-the-art microscopy techniques are in general limited to surface investigation or require elaborate tissue preparation and often destruction. X-ray microscopy has the potential to resolve some of these limitations by generating micro- to nanometer-scale 3D images deep in the tissue. We introduce experimental designs and quantitative analysis methodologies, pioneering <i>in vivo</i> 3D microscopy of plant tissue down to 50 nm isotropic voxel size. We show direct <i>in vivo</i> visualization of foliar-applied untagged clustered nanoparticulate fertilizers deep under the leaf surface, not accessible by other microscopy methods. The clustering of nanoparticles occurs naturally for MSN particles and is induced by CaCl₂ for nPAA-MnO₂ particles. Ultimately, our approach provides the means for direct observation of nanoparticle transport and dissolution in living plant tissue, a step critical for developing sustainable plant fertilization approaches.