The Effects of Saline–Alkali Stress on Taxodium “ Zhongshanshan302 ”: Insights Into Wood Formation and Metabolic Adaptation

Saline-alkali soils, commonly found in coastal regions, impose substantial environmental stress on trees, affecting both growth and wood formation. The mechanisms through which trees adapt to these conditions are multifaceted, primarily involving physiological and biochemical responses. Therefore, the impact on wood properties and associated metabolic pathways warrants further exploration. Two-year-old Taxodium "Zhongshanshan302" seedlings were cultivated in salinized soil, simulating the saline-alkali ion ratio typical of a coastal mudflat. The response of wood-forming tissues to salt-alkali stress was investigated through wood anatomy techniques, cell wall chemical analysis, and metabolomic profiling. The study demonstrated that mild to moderate saline-alkali stress promoted growth, enhancing lignification and cellulose crystallinity, while severe stress led to reduced lignin synthesis and delayed tracheid lignification. Moreover, metabolite analyses suggested that severe saline-alkali stress was associated with changes in carbohydrate metabolism and phenylpropanoid-related metabolism, which may contribute to reduced cellulose deposition and lignification in "Zhongshanshan302." A distinctive mode of cellular osmotic regulation under saline-alkali stress was also delineated. The complex interplay between wood formation and saline-alkali stress responses was highlighted, providing valuable insights for tree management and wood production in affected regions.