Atriplex prostrata Boucher, a facultative halophyte, exhibits significant reduction in height and biomass and in the width of the cortex and vascular tissue under saline conditions. Therefore, the goal of this investigation was to determine the effect of salinity on plant growth as well as on the patterns of lignification, peroxidase activity, and extensin deposition. Biomass, leaf area, internode length, water potential, photosynthesis, transpiration, and ion content were measured. In addition, lignin, peroxidase, and extensin were, respectively, examined via phloroglucinol staining, peroxidase staining, and immunostaining with extensin antibody on tissue prints of free-hand stem sections. Length of internodes and leaf area significantly decreased with increased salinity, and net photosynthesis declined dramatically as well. There was a significant accumulation of Na+ in organs when plants were grown in saline solutions, while the concentration of K+, Ca2+, and Mg2+ decreased. The signals in tissue prints showed that soluble peroxidase and extensin accumulated in the first three internodes of A. prostrata grown under saline conditions. In contrast, lignification was reduced under saline growth conditions in the third and fourth internodes. These results indicate that extensin may replace lignin in providing mechanical support for cells, while stems remain in a juvenile stage because of growth retardation caused by salinity.