Exploring architectural cell wall heterogeneity: Celery collenchyma as a case study

The colonisation of land by plants ~470 MYA initiated a period of extensive morphological diversification in concert with an equally impressive diversification in anatomy. Immobility has forced plants to acquire the ability to adapt to environmental challenges, which in turn has impacted plant diversity. These evolutionary events and mechanisms have contributed to the generation of complex body plans that require meticulously controlled differentiation of tissues and cells throughout growth and development, and this specialisation is reflected in the molecular design and dynamic nature of their cell walls. Architectural heterogeneity within a single cell wall may involve compositional and/or structural differences and is controlled spatio-temporally in such a way that small changes in wall architecture may have profound effects on the functional performance of the cell wall; thus underpinning organ and tissue growth, differentiation and development. While analysis of fractionated cell walls yields detailed structural information for individual polymers it results in destruction of the supramolecular organisation essential for understanding cell wall complexity, heterogeneity and dynamics. However, a range of methods for detailed in situ examination are available. Distinct lamellation of celery collenchyma cell walls has been observed using transmission electron microscopy and we further investigated this heterogeneous feature using immunocytochemistry, electron tomography, as well as Raman spectroscopy and chemometrics. Is collenchyma cell wall architectural heterogeneity caused by structural and/or compositional variation?