Abstract: Taking Polygonatum zanlanscianense and Polygonatum sibiricum as the research objects, two light treatments (full sunlight and 60%-65% shading) were established to evaluate the effects of light environment on maximum leaf morphology, stem diameter, chlorophyll SPAD values, and photosynthetic parameters of the two Polygonatum species. The results showed that shading made the leaves of both species thinner and more elongated. The leaf length and leaf shape index of Polygonatum zanlanscianense reached their maximum values under shading. Shading had no significant effect on stem diameter, which was mainly determined by species. Two-way analysis of variance (ANOVA) showed that species had a significant (P<0.05) or highly significant (P<0.01) influence on most morphological and photosynthetic indicators, with the exception of chlorophyll SPAD value. Shading significantly regulated leaf length (P<0.05), leaf width (P<0.01), leaf shape index (P<0.01), and leaf area (P<0.01). The interaction between the two factors had a significant effect only on leaf shape index (P<0.01). For Polygonatum zanlanscianense, leaf area showed strong linear correlations with leaf length (R²=0.90) and leaf width (R²=0.89) under shading, whereas the correlations among morphological indicators of Polygonatum sibiricum were generally not significant across all light treatments, indicating that Polygonatum zanlanscianense had stronger morphological plasticity in maximum leaves. In terms of photosynthetic parameters, Polygonatum sibiricum showed the highest net photosynthetic rate and transpiration rate under full sunlight. Polygonatum zanlanscianense had the lowest chlorophyll SPAD value under shading, and its intercellular CO₂ concentration was significantly lower than that of Polygonatum sibiricum. Species had a significant effect on transpiration rate, net photosynthetic rate, chamber CO₂ concentration, and intercellular CO₂ concentration, whereas shading and the interaction had no significant effects on these photosynthetic parameters. Polygonatum zanlanscianense and Polygonatum sibiricum showed interspecific differences in morphological plasticity and photosynthetic physiology, and therefore zone-based cultivation should be implemented in production based on their light adaptability.

Key words: Polygonatum zanlanscianense, Polygonatum sibiricum, shading, leaf morphology, photosynthetic physiology, interspecific difference