Supramolecular Assembly of Cell Wall Anisotropic Scatterers in Triticale Root Apex Reflects Aluminum Stress Response in Contrasting Genotypes

Acid soil aluminum (Al) considerably reduces crop productivity. This study examined whether transformation of supramolecular assembly of root cell wall polysaccharides (CWPs) contributes to genotype-specific responses to Al stress in triticale. CWPs were extracted from apical and hairy root segments of two triticale genotypes, differing in Al tolerance. Water-extractable polysaccharides (WEPs) and those extracted with trans-1,2-cyclohexanediaminetetraacetic acid (CDTA) and sodium carbonate (Na₂CO₃) were analyzed using the multi-detection high-performance size-exclusion chromatography (HPSEC-RI-LALS/RALS-DV-UV-Vis). WEPs most clearly reflected differences between genotypes in macromolecular organization and Al-induced modification. Both root segments contained high molar mass (HM) subunits of WEPs with distinct anisotropic light scatterer (AS) domains. AS domains of a tolerant genotype were symmetrically elongated and branched, whereas those of a sensitive one were asymmetrically elongated with a spherical shape. In both genotypes, Al stress induced an association of apical HM subunits to higher molar mass forms, but in a different manner. The tolerant genotype maintained branched AS domain architecture by forming separate HM subunits that prevented Al infiltration. In contrast, the sensitive genotype showed complete merging of all HM subunits into a micro gel structure, leading to AS surface degradation. These findings provide novel insight into the role of root AS domains and supramolecular cell wall organization in plant adaptation to abiotic stress.