Tissue-specific cell wall hydration in sugarcane stalks

Plant cell walls contain water, especially under biological and wet processing conditions. The present work characterizes this water in tissues of sugarcane stalks. Environmental scanning electron microscopy shows tissue deformation upon drying. Dynamic vapor sorption determines the equilibrium and kinetics of moisture uptake. Thermoporometry by differential scanning calorimetry quantifies water in nanoscale pores. Results show that cell walls from top internodes of stalks are more deformable, slightly more sorptive to moisture, and substantially more porous. These differences of top internode are attributed to less lignified walls, which is confirmed by lower infrared spectral signal from aromatics. Furthermore, cell wall nanoscale porosity, an architectural and not directly compositional characteristic, is shown to be tissue-specific. Nanoscale porosities are ranked as follows: pith parenchyma > pith vascular bundles > rind. This ranking coincides with wall reactivity and digestibility in grasses, suggesting that nanoscale porosity is a major determinant of wall recalcitrance.