【摘要】 【目的】研究不同遮阴处理对明日叶光合色素含量和光合特性的影响，为明日叶的林下种植及其耐阴性评价提供理论依据。【方法】以6个月生明日叶实生苗为供试材料，采用盆栽试验，设不遮阴对照、轻度遮阴（遮阴率30%）、中度遮阴（遮阴率50%）和重度遮阴（遮阴率70%）4个处理，于遮阴30、60和90 d时取样测定功能叶的光合色素含量，于遮阴90 d时测定叶片的光合特性，分析各指标的变化及其相关性。【结果】随着遮阴程度增加，3个遮阴处理的叶绿素a（Chla）、叶绿素b（Chlb）、总叶绿素（Chlt）和类胡萝卜素（Car）含量及叶绿素a/叶绿素b（Chla/Chlb）均呈先升高后降低的变化趋势，中度遮阴处理下叶绿素含量显著高于其他处理（P<0.05，下同）。光响应参数变化趋势存在差异，表观量子效率（AQY）和光饱和点（LSP）先升高后降低，最大净光合速率(P_max)先升高后降低再升高，光补偿点（LCP）持续下降，暗呼吸速率（R_d）先降低后升高再降低。净光合速率（P_n）日变化呈单峰曲线，气孔导度（G_s）和蒸腾速率（T_r）整体呈先升高后降低的变化趋势，胞间CO₂浓度（C_i）日变化呈V形曲线，气孔限制值（L_s）日变化在各处理间变化规律不一致。相关分析结果表明，P_n与L_s呈极显著正相关（P<0.01，下同），与C_i、AQY和叶绿素含量呈极显著负相关，与LSP和Car呈显著负相关；光合色素含量均与光合有效辐射（PAR）、T_r、G_s、LCP、R_d呈极显著负相关，与AQY呈极显著正相关；其他指标间也存在不同程度的相关性。【结论】适度遮阴条件下，明日叶可通过提高叶绿素含量，增强其对弱光的捕获和利用能力，从而适应低光环境，表现出较强的光能利用率和光合能力。不同遮阴处理下明日叶的P_n日变化为单峰曲线，未出现由于强光抑制导致的光合午休现象，C_i升高、L_s降低导致的P_n下降是限制其光合作用的主要原因。更多还原

【Abstract】 【Objective】This study aimed to investigate effects of different shading treatments on photosynthetic pigment content and photosynthetic characteristics of Angelica keiskei, thereby providing a scientific reference for the understory planting of Angelica keiskei and evaluation of its shade tolerance mechanism. 【Method】The 6-month-old Angelica keiskei seedlings were used as the test materials to carry out the pot experiment. Four treatments were set up: no shading control, mild shading（shading rate of 30%）, moderate shading（shading rate of 50%） and severe shading（shading rate of 70%）. The photosynthetic pigment content of functional leaves was measured after 30, 60 and 90 d of shading, and the photosynthetic characteristics of leaves were measured after 90 d of shading to analyze the changes of each index and their correlations. 【Result】With the increase of shading degree, the chlorophyll a（Chla） content, chlorophyll b（Chlb） content, total chlorophyll content, and chlorophyll a/chlorophyll b（Chla/Chlb） of the three shading treatments increased first and then decreased, and the chlorophyll content under moderate shading treatment was significantly higher than that under other treatments（P<0.05, the same below）. The change trends of light response parameters were different: the apparent quantum yield（AQY） and light saturation point（LSP） increased first and then decreased; the maximum net photosynthetic rate(P_max) increased first, then decreased and then increased; the light compensation point（LCP） continued to decrease; and the dark respiration rate（R_d） decreased first, then increased and then decreased. The diurnal variation of net photosynthetic rate（P_n） showed a single-peak curve; the stomatal conductance（G_s） and transpiration rate（T_r） increased first and then decreased; the diurnal variation of intercellular CO₂ concentration（C_i） showed a V-shape curve; the diurnal variation of stomatal limitation（L_s） was inconsistent across treatments. The results of correlation analysis showed that P_n had a highly significant positive correlation with L_s（P<0.01, the same below）, but P_n had highly significant negative correlations with C_i, and AQY, significantly positive correlations with LSP and Car; photosynthetic pigment content had highly significant negative correlations with photosynthetic active radiation（PAR）, T_r, G_s, LCP, and R_d, but it had a highly significant positive correlation with AQY; other parameters were correlated to different extents. 【Conclusion】Appropriate shading conditions can enhance the ability of Angelica keiskei to capture and utilize weak light by increasing chlorophyll content, so as to adapt to low light environment, showing a strong light energy utilization and photosynthetic capability of Angelica keiskei. The diurnal variation curves of P_n under different shading treatments are single-peak, showing no indicating no midday depression of photosynthesis caused by strong light inhibition, therefore, the increase of C_i and decrease of L_s are the main reasons for the decrease of P_n, which mainly limit the photosynthesis of Angelica keiskei.更多还原