Effect of silicon-based fertilization against drought stress in maritime pine seedlings

The increase in the frequency and severity of drought events caused by climate change poses a serious threat to the sustainability of forest ecosystems. In this context, raising resistant individuals to environmental stresses at the nursery stage has become a priority target in forestry practices. In this study, the potential of silicon (Si)-based fertilizer to increase drought tolerance through physiological and morphological responses in maritime pine (Pinus pinaster Aiton) was investigated. Within the scope of the research, silicon was applied to 1+1-year-old maritime pine seedlings at doses of 0, 5, 10, 15 and 30 g; physiological [Photosynthetic activity (Fv/Fm), minimum fluorescence (Fo), maximum fluorescence (Fm), relative water content (RWC), moisture content (MC)], morphological (diameter and height increase, sturdiness quotient) and visual stress responses were evaluated under four-week drought conditions. Two-way analysis of variance revealed that treatment (drought/irrigation) × dose interaction had statistically significant effects on Fv/Fm (p=0.009), Fo (p=0.021), Fm (p=0.044) and MC (p=0.044). The results showed that seedlings treated with silicon in the range of 5–15 g exhibited higher photosynthetic efficiency (Fv/Fm), water holding capacity (RWC, MC) and visual scores under drought. In contrast, high doses (30 g) had negative effects on some physiological parameters. Although no significant differences were observed in the morphological parameters in the short term, growth trends showed that medium doses provided more balanced development. The present study suggests that silicon-based fertilizer at the nursery stage may be a viable strategy for stress management by increasing physiological resistance in drought-tolerance species such as maritime pine.