Abstract: To provide a theoretical basis for field conservation and scientific cultivation of endangered plant Magnolia sinostellata, we investigated its adaptation mechanism to different light environments. The changes of morpholo-gical structures, stoichiometry and non-structural carbohydrates in two-year-old seedlings of M. sinostellata were examined under three light conditions: full light intensity (I₁₀₀), 40% light intensity (I₄₀), and 10% light intensity (I₁₀). The results showed that: (1) Leaf length, leaf width, leaf circumference, and leaf area of M. sinostellata seedlings under I₄₀ were the largest, while leaf water content and specific leaf area significantly increased with decreasing light intensities. (2) The stomatal density and stomatal area percentage of M. sinostellataseedlings under I₁₀₀ were significantly higher than those under I₄₀ and I₁₀. (3) Leaf thickness and palisade tissue of M. sinostellata seedlings under I₁₀₀ and I₄₀ were significantly higher than those under I₁₀. Surface area of mesophyll intercellular space/unit leaf area (S_mes) and chloroplast surface area/unit leaf area (S_c) of M. sinostellata seedlings under I₄₀ were significantly lower than those under I₁₀₀ and I₁₀. Chloroplast number per unit area (n_chr) of M. sinostellata seedlings under I₁₀ were the largest. (4) The N content and N∶P under I₁₀ were significantly higher than those under I₁₀₀ and I₄₀, which suggested that heavy shading could increase enzyme activities and chlorophyll content of photosynthesis. (5) Soluble sugar and non-structural carbohydrate (NSC) in the shading treatments were significantly higher than those under I₁₀₀. In conclusion, M. sinostellata seedlings had higher leaf area, S_mes and S_c, tighter leaf structure, and enhanced CO₂ utilization ability under I₄₀. Shading treatment led to higher NSC content. As a shade-tolerant woody species, moderate shading can alleviate the limitation of high temperature and drought on seedling growth in summer, but the shading intensity should not be too high. The effective light intensity should be kept above 40% of natural light intensity.

Key words: light intensity, Magnolia sinostellata, morphological and anatomical characteristics, stoichiometry, non-structural carbohydrate.