Enhancing Cabbage Palm Resilience to Saltwater Stress through Silicon Applications

Saltwater intrusion driven by climate change increasingly imperils Florida’s coastal ecosystems. This study investigated whether silicon amendments can buffer cabbage palm ( Sabal palmetto ) seedlings against saline stress. One-year-old seedlings were irrigated with seawater analogues at 10, 30, or 50 ppt (ranging from freshwater to hypersaline conditions) and supplemented with soluble silicon at 1%, 3%, or 5% (m/v). Vigor was quantified nondestructively using SPAD-502 and atLEAF+ meters that estimated the chlorophyll content and measurements of height and leaf number. Salinity alone decreased all growth variables, with the steepest declines observed with 50 ppt. Silicon markedly mitigated losses in chlorophyll content, height, and leaf production at 10 through 30 ppt and partially preserved performance at 50 ppt; however, overall survival remained poor at the highest salinity. The results revealed a low inherent salt-tolerance threshold during early ontogeny; however, they demonstrated that silicon can extend that threshold and improve the physiological status under moderate intrusion scenarios. These findings furnish actionable guidance for nursery production and restoration of cabbage palm as the rise in sea level accelerates saltwater encroachment in Florida’s coastal landscapes.