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 in vivo 3D microscopy of plant tissue down to 50 nm isotropic voxel size. We show direct in vivo 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.