Cell wall remodeling and polarized light analysis reveal ecotype-specific strategies in Salicornia europaea L. with biotechnological applications.

Salicornia europaea, a salt-tolerant halophyte, exhibits dynamic cell wall remodeling under salinity stress, offering a valuable model for understanding biopolymer adaptation and sustainable biomass valorisation. This study investigates how increasing NaCl concentrations (0, 200, 400, and 1000 mM) alter the composition and mechanical behaviour of key cell wall polymers cellulose, pectin, and lignin in an inland S. europaea population. Using atomic force microscopy, fluorescence-based imaging, pectin immunolocalization and polarized light microscopy, we demonstrate that salinity drives tiered changes in polymer deposition and stiffness. Optimal salinity (200-400 mM) induced cell wall softening, linked to reduced cellulose deposition and increased pectin methylesterification, which facilitate turgor maintenance and expansion. Lignin composition shifted toward syringyl-rich polymers, promoting elasticity and enhancing apoplastic water flow. At extreme salinity (1000 mM), cell walls exhibited reduced flexibility and altered lignin monomer profiles, favoring p-hydroxyphenyl units as a cost-saving adaptation. These biochemical shifts were accompanied by a spatial reorganization of tissue birefringence. By mapping polymer-specific responses to salinity, we provide a mechanistic framework for optimizing cell wall composition in S. europaea to enhance functional value. Our findings support the targeted cultivation of halophytes for applications in functional foods, plant-based therapeutics, and more efficient biofuel feedstocks under saline agriculture.