Visualising Physcomitrium patens protoplasts with full-rotation soft X-ray tomography.

Soft X-ray tomography (SXT) is a label-free, high-resolution imaging modality that is optimal for 3D visualisation of whole hydrated cells. Although SXT has been extensively used to study remodelling in more than 130 mammalian cell lines, its application to plants remains largely unexplored. In this study, we present the first approach at full-rotation SXT imaging of spreading earthmoss P. patens, which is a key model organism for studying plant cell architecture and developmental processes. We show that high-resolution, three-dimensional imaging of fully hydrated P. patens protoplasts enable visualisation of organelle morphology and distribution. These proof-of-concept results demonstrate the potential of SXT to capture ultrastructural changes in plant cells, depending on developmental cues, stress responses, and genotype-dependent variation.