Physiological adaptations to different shade levels and their role in enhancing yield and quality of Ficus formosana Maxim. for under-forest economy: Insights from greenhouse and forest environments

Ficus formosana Maxim., an emerging under-forest economic crop, adapts to understory environments but exhibits growth variations under different canopy and light conditions. This study analyzed the growth, physiological, and biochemical responses of F. formosana under three shading gradients in greenhouse and broadleaved forest environments to evaluate the effects of light intensity on plant performance. After eight months, plants in unshaded forest environments showed increased hydrogen peroxide and malondialdehyde levels and reduced Fv/Fm, indicating oxidative stress and photosystem damage. In contrast, severe shading promoted chlorophyll content, specific leaf area, and leaf area ratio, enhancing light capture, but restricted stomatal conductance and carbon assimilation, ultimately limiting metabolite production and biomass accumulation. Growth patterns in the greenhouse were consistent with those in the forest. However, physiological and morphological adaptations were observed across all shading conditions in the forest, highlighting the excellent shade tolerance and adaptive regulation of F. formosana in the understory environment. Optimal growth occurred under moderate shading, with 21 % relative light intensity and a daily light integral of ∼4 mol photons m⁻² day⁻¹, achieving the highest biomass and stable root secondary metabolite levels and DPPH scavenging activity. These findings underscore the critical role of optimizing light intensity in the cultivation of under-forest economic crops. For F. formosana, moderate shading provides the most favorable conditions for maximizing root yield, while simultaneously maintaining its antioxidant quality, thereby enhancing its economic viability.