Abstract text: Morphogenesis relies on the coordinated interplay between the cytoskeleton and cell wall, where cellulose microfibril organisation and wall mechanics are important determinants of cellular shape. FASS knockout lines, a component of the plant microtubules (MT)-regulating TTP complex, were first described as preprophase band-less mutants, and later as exhibiting strong defects in interphase microtubule nucleation and reorientation dynamics. Although the mutant still undergoes normal histogenesis, loss of FASS function contributes to defects in post-cytokinetic cell morphogenesis. Since coordination of microtubules with cell wall (CW) cellulose microfibril orientation plays a pivotal role in determining the direction of cell elongation, we analysed anisotropy and orientation changes of cortical MT arrays together with selected mechanical and compositional features of the CW in moss Physcomitrium dwarf fass mutants and wild type. Imaging using fluorescent cellulose stains, high-resolution scanning electron microscopy, Raman spectroscopy, and Brillouin microscopy revealed considerable differences in the organisation of cell surface structures, cellulose microfibril patterns, and wall mechanical properties in mutants compared to wild type, resulting in a significantly stiffer CW in fass mutant. Their correlation with microtubular cytoskeleton orientation and dynamics provides further insights into moss morphogenesis and a useful framework for quantitative cell wall analysis. Supported by GACR/CSF project 23-05564S.