Medicinal plant-based agroforestry systems have considerable economic benefits.In the present study, the changes in the photosynthesis and growth of the early spring plant, Corydalis yanhusuo, under different light conditions were analyzed.This was done to provide a scientific basis for understory tending, canopy thinning, and development of medicinal plant-based agroforestry systems using this species.It was found that C.yanhusuo adapted to shaded and low-light environments by decreasing its light saturation point, light compensation point, and dark respiration rate, and increasing its apparent quantum yield.Differences in the performance of C.yanhusuo under full-and medium-light conditions were not significant.Particularly, the mean values for dark respiration rate and maximum net photosynthetic rate under medium-light conditions were higher than those under full-light conditions.The saturation light intensity, maximum net photosynthetic rate, and apparent quantum yield under low-light conditions were 62.67％, 43.25％, and 58.42％of the values under full-light conditions, respectively.The net photosynthetic rate, stomatal conductance, and transpiration rate under shaded conditions were generally lower than the corresponding values under full-light conditions.After shading, Chl a, Chl b, and Chl a+Chl b levels in the leaves of C.yanhusuo initially increased and subsequently decreased as photosynthetically active radiation decreased.Under medium-high-and medium-low-light conditions, the Chl a:Chl b ratio significantly decreased.This demonstrates the shade tolerance of this species, whereas the significant decrease in the Chl a:Chl b ratio under low-light conditions is attributed to the insufficient supply of photosynthates and reduced chlorophyll synthesis caused by low light.The leaf and root biomasses of C.yanhusuo under low-light conditions were only 34.78％and 22.03％of the values obtained under full-light conditions, respectively.With a decrease in photosynthetically active radiation, the specific leaf area initially increased and subsequently decreased, indicating that C.yanhusuo prioritizes the morphological construction of leaves over the expansion of leaf area to capture more photons under low-light conditions.The shade tolerance of C.yanhusuo is intermediate between that of light-demanding plants and shade plants, and the photosynthetic apparatus of C.yanhusuo may become similar to that of shade-tolerant plants under low-light conditions.Therefore, C.yanhusuo has a certain level of shade tolerance, but it is not well-suited for long-term exposure to low-light conditions.During the cultivation of C.yanhusuo in wild woodlands with very high canopy closure, measures such as appropriate thinning and pruning, or creation of forest gaps, can improve understory light environment and enhance photosynthetic capacity and sunfleck utilization of understory C.yanhusuo plants.These measures can then allow for reasonable allocation of light and temporal niches for the plants to achieve the expected economic benefits.%林-药复合系统是经济收益显著的立体林农生态系统.以早春植物延胡索为研究对象, 分析其不同光环境下光合与生长的变化, 为其林下抚育、林木间伐和林药复合生态系统的构建提供依据.试验发现, 延胡索通过降低光饱和点、光补偿点和暗呼吸速率, 提高表观量子效率等方式以适应遮阴和弱光环境;在高光照和中高光照条件下, 延胡索对两种光环境表现差异不显著, 在暗呼吸速率和最大净光合速率方面, 中高光照条件的均值甚至超过高光照条件;弱光条件下的饱和光照强度、最大净光合速率和表观量子效率分别为高光照的62.67％、43.25％和58.42％.遮阴条件的净光合速率、气孔导度和蒸腾速率总体均低于高光照条件.遮阴后, 延胡索叶片的Chl a、Chl b及Chl a+Chl b皆随着有效光辐射的下降呈现先升后降的趋势, Chl a/Chl b值在中高光照和中低光照条件下显著降低, 表现出耐阴性能, 而弱光条件下Chl a/Chl b值显著下降的原因是弱光导致延胡索的光合产物供应不足, 妨碍了叶绿素的合成.弱光下延胡索叶生物量、根生物量分别仅为高光照条件下的34.78％和22.03％;随着有效光辐射的下降, 比叶面积先升后降, 在弱光条件下延胡索优先于叶片的形态构成, 而不再倾向于扩大叶面积捕获更多的光量子.延胡索耐阴能力介于阳性植物和阴性植物之间, 弱光下的延胡索光合机构可能已向耐阴植物转变.因此, 延胡索具有一定的耐阴能力, 但并不适合长期的弱光条件.野外疏林下进行仿野生延胡索栽培时, 当乔冠层的郁闭度过高时, 可适当采取间伐修枝或者开辟林窗等措施改善林下光环境, 提升林下延胡索的光合作用能力和光斑利用效率, 合理配置其光生态位和时间生态位以达到预期的经济效益.
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