Changes in elemental composition and cell wall phenolics in maize leaves under water deficit: Implications for drought performance

Leaves are a key organ for studying drought tolerance in maize because they integrate the physiological and biochemical processes governing carbon assimilation, water loss, and plant growth under water deficit. Within leaves, the cell wall provides mechanical support and may undergo compositional remodelling that contributes to maintaining tissue integrity and regulating growth during drought. However, the specific roles of elemental traits and cell wall-bound phenolics in the leaves under field drought conditions remain poorly understood. We evaluated 15 diverse Mediterranean maize inbred lines over two years under well-watered and water-deficient field conditions, using three replicate plots per genotype and water regime. The cumulative effects of field-imposed water deficit were assessed in ear-adjacent leaves collected 30 days after silking. Drought reduced plant height, biomass yield, leaf nitrogen and δ¹⁵N concentration, while increasing the C:N ratio. Water deficit also increased cell wall-bound p-coumaric acid, ferulic acid, and diferulates, whereas lignin content remained unchanged, indicating that cell-wall composition in the leaves involve enhanced hydroxycinnamates cross-linking rather than increased lignin deposition. Across inbred lines, lines showing greater biomass reductions also showed larger decreases in leaf nitrogen and greater increases in hydroxycinnamates concentrations, whereas lines showing lower biomass reductions exhibited smaller changes in these traits. Overall, leaf nitrogen preservation and restrained hydroxycinnamates contents in the leaves emerge as candidate traits for assessing maize biomass maintenance under water deficit.