Abstract text: Using flax fibers and celery collenchyma, we examine two model systems representing thickened non-lignified cell walls that share a mechanical function but implement it through distinct strategies, participants, and mechanisms.

Collenchyma primary cell walls function exclusively hydrated. Their pectin-rich, xyloglucan-depleted matrix with polylamellate architecture undergoes specific remodeling during growth, enabling elongation despite possessing a thickened cell wall. In fibers, the hydrostatic skeleton operates at early stages, transitioning to accentuated mechanics as the highly ordered tertiary cell wall develops, featuring longitudinally oriented cellulose microfibrils with rhamnogalacturonan I “entrapped” between them and modified during cell wall maturation.

The report provides detailed structural-functional characterization of both systems, emphasizing specific non-cellulosic polysaccharide composition, patterns of polysaccharide-cellulose “relationships:”, and post-synthetic modifications that determine strategies for growth and mechanical function. These are considered within the organ-level context of collenchyma and phloem fiber localization.

The work was partially supported by the RSF #24-14-00383.