Silicon Addition Alleviates Light Stress on Seedlings: Evidence from Plantation of Liquidambar formosana

Excessive light intensity, often resulting from anthropogenic disturbances, poses a threat to light-sensitive <i>Liquidambar formosana</i> seedlings. This study examined the effects of five light intensity levels and three silicon (Si) application rates on photosynthetic performance, oxidative stress responses, and seedling growth. Results indicated that full sunlight significantly reduced ground diameter, chlorophyll content, specific leaf area, and stomatal conductance. Meanwhile, it increased the activities of superoxide dismutase and peroxidase, and led to higher accumulation of malondialdehyde (MDA). Application of Si enhanced seedling height, biomass accumulation, and antioxidant enzyme activity under high-light conditions, while reducing MDA content, stomatal CO₂ conductance, and transpiration rate, and maintaining a stable net photosynthetic rate. However, excessive Si (3000 mg·kg^-1) led to decreased catalase activity, chlorophyll content, and leaf area under intense light. These findings suggest that <i>L. formosana</i> seedlings perform best under moderate shade (11,000-46,000 lx) and moderate Si application (1000-2000 mg·kg^-1), which together mitigate photoinhibition damage. Optimal physiological responses thus require balanced Si concentrations. Further investigation is warranted to elucidate the mechanisms underlying the interactive effects of shading and Si application for improved seedling resilience.