【作者】 李海涛；

【导师】 刘艺平； 李文玲；

【作者基本信息】 河南农业大学 ， 风景园林硕士（专业学位）， 2025， 硕士

【摘要】 随着中国城市化进程加速,高架桥在城市交通中发挥重要作用,但其引发的环境污染问题日益严峻。高架桥桥阴绿化是缓解此类问题的重要措施。然而,由于桥阴区域光合有效辐射显著不足,动态弱光环境对植物的光照适应性和耐阴性要求较高,导致大多数植物生长不良甚至死亡,桥阴区域绿化效果差、养护成本高。因此,研究不同类型高架桥桥阴区域的弱光环境及其他生境特征,并分析不同绿化植物对高架桥桥阴动态弱光环境响应策略及可塑性调节机制,有助于筛选适应光照范围广、耐阴性强的植物,并促进高架桥桥阴绿化的科学发展。本研究以郑州市三环内31座高架桥为调研对象,选取4座具有代表性的高架桥,重点分析桥阴生态环境,特别是光照特征。根据4座高架桥桥阴绿化区的光照率范围,选取光照差异显著的两座高架桥,以全光照环境为对照,构建光强逐渐降低的三种光环境:公园（近100%全光照环境,CK）、南北走向京广高架桥（22.36%-27.33%光照率,T1）与东西走向高架农业路高架桥（4.42%—7.43%光照率,T2）。通过测定郑州市4种典型桥阴绿化植物（麦冬Ophiopogon japonicus、海桐Pittosporum tobira、卫矛Euonymus alatus和小蜡Ligustrum sinense）在三种光环境下的叶片形态、生理光合作用及叶绿素荧光参数,探讨它们在桥阴弱光环境下的适应策略及表型可塑性调节机制,主要结论如下:1、光照强度是影响桥阴植物生长的关键生态因子。桥体走向、高宽比（H/W）及周围环境等因素均会影响其光照条件。南北走向高架桥桥阴区域光照率较高且分布均匀,东西走向桥阴区域光照率低且分布不均。桥体H/W较大时,桥阴光照条件较优,而高架引桥段净空高度低的区域光照极差,部分区域形成植物生长的“死区”。桥阴区域温湿度变化与光照强度相关,温度低于桥外无遮阴区域,湿度较高,但桥阴土壤较为干旱、呈弱碱性,含水率低,盐度高,可能对植物生长形成限制。2、四种植物叶片形态结构在桥阴弱光环境下显著变化。比叶面积（SLA）、气孔密度（SD）随光照降低而增加,表明植物通过扩大捕光面积和减少蒸腾作用以适应弱光环境。同时,比叶重（SLW）、叶片厚度（LT）、栅栏组织厚度（PT）、海绵组织厚度（ST）等随光照降低而下降,反映植物通过叶片轻薄化降低能量消耗,并优化解剖结构提升光能捕获效率。3、随着光照强度的降低,海桐、卫矛和小蜡的净光合速率（P_n）、气孔导度（G_s）、胞间二氧化碳浓度（C_i）与蒸腾速率（T_r）等光合参数普遍下降,光合能力在桥阴弱光环境中受限。相反,麦冬的光合参数在适度弱光环境（T1）下先升高后下降,表明其在适度桥阴条件下能够最大化光能利用,表现出较高的光合效率。各植物的水分利用效率（E_w）随光照强度降低呈先升高后下降的趋势,表明适度弱光环境有助于优化水分利用,而在极低光照下（T2）抑制植物的生长和适应能力。4、不同植物在桥阴弱光环境中的叶绿素荧光参数的变化存在显著差异。麦冬在T1条件下表现出PSII反应中心活性最强,叶绿素荧光参数(F_v/F_m、F_v’/F_m’和PI_ABS)显著提升,展现较高光化学效率与电子传递能力。相比之下,海桐、卫矛和小蜡的荧光参数随光照降低持续下降,PSII活性和光化学效率显著减弱。5、桥阴弱光环境对植物生理指标的影响显著。光照减弱时,植物叶绿素a、b含量、可溶性蛋白（SP）、丙二醛（MDA）、相对电导率（REC）、超氧化物歧化酶（SOD）和过氧化物酶（POD）活性均增加,而叶绿素a/b比值显著下降。植物通过增加叶绿素含量提高光能捕获效率,同时通过可溶性蛋白积累和抗氧化酶活性增强抗氧化防御机制,从而减轻弱光胁迫对细胞膜的氧化损伤。6、四种植物的整体表型可塑性依次为麦冬>卫矛>海桐>小蜡。麦冬表现出最强的可塑性,特别在光合效率和抗氧化调节方面,通过增加叶绿素和可溶性蛋白含量,优化光捕获与碳同化。卫矛在光合特征和生理调节上具有较高可塑性,通过增强光合作用和抗氧化能力适应弱光环境,并调整解剖结构提高光利用效率。海桐则在叶绿素积累、抗氧化物质调节及叶面积优化方面具有较强的可塑性,但光能转换效率调节能力有限。小蜡的可塑性最差,主要依赖于过氧化物酶活性和叶片厚度调整,对弱光环境的耐受性较差。麦冬对桥阴动态弱光环境具有优越适应能力,适应范围较广,且在适度弱光环境下保持较高的光合效率;卫矛和海桐次之,而小蜡则不适宜在此类环境下生长。综合分析,植物的可塑性主要通过光合特征与生理特性来体现,较高的光合指标（P_n、T_r、G_s）与生理指标（Chlab、POD、SP）可塑性是植物适应桥阴弱光环境的关键策略.因此,在对城市高架桥桥阴区域进行绿化时,应充分考虑桥阴光照环境与不同植物品种的适应光照范围,选择具有较高光合与生理可塑性的植物,如麦冬,卫矛,最大程度保证桥阴绿化植物的正常生长发育,确保桥阴绿化的生态价值与效益。更多还原

【Abstract】 With the rapid urbanization process in China,viaducts play a significant role in urban transportation,but the environmental pollution issues caused by viaducts have become increasingly prominent.The greening of viaduct shaded areas is an important measure to mitigate these issues.However,due to the significant lack of photosynthetically active radiation in shaded areas,the dynamic low-light environment poses high requirements for plants’light adaptation and shade tolerance,resulting in poor growth or even death of most plants,leading to ineffective greening and high maintenance costs.Therefore,studying the low-light environment and other habitat characteristics of different types of viaduct shaded areas and analyzing the response strategies and plasticity mechanisms of various greening plants can aid in selecting plants with broad light adaptability and strong shade tolerance,promoting the scientific development of viaduct greening.This study investigated 31 viaducts within the third ring road of Zhengzhou,selecting 4 representative viaducts,and focused on analyzing the ecological environment of the shaded areas,especially the light characteristics.Based on the light intensity range of the four viaducts,two viaducts with significantly different light levels were chosen as the study sites.Three light environments were constructed:full light（CK）,the north-south oriented Jingguang viaduct（22.36%-27.33%light）,and the east-west oriented Agricultural Road viaduct（4.42%-7.43%light）.By measuring the leaf morphology,physiological photosynthesis,and chlorophyll（Chl）fluorescence parameters of four typical plants（Ophiopogon japonicus,Pittosporum tobira,Euonymus alatus,Ligustrum lucidum）under these three light conditions,the study explored their adaptation strategies and phenotypic plasticity regulation mechanisms in low-light environments.The main conclusions were as follows:1.Light intensity is critical ecological factor affecting plant growth in viaduct shaded areas.Factors such as bridge orientation,height-to-width ratio（H/W）,and surrounding environment all affect light conditions.The north-south oriented viaduct has higher and more uniform light intensity in its shaded areas,while the east-west oriented viaduct exhibits lower and more uneven light distribution.The shaded areas with larger H/W ratios had better light conditions,while areas with lower clearance at the bridge ramps exhibited poor light conditions,forming"dead zones"for plant growth.The temperature and humidity changes in shaded areas were correlated with light intensity,with the temperature in the shaded area being lower than that in the open areas,while humidity was higher,but the soil in shaded areas was dry,weakly alkaline,with low water content and high salinity,which could limit plant growth.2.The leaf morphological structure of the four plants showed significant changes in low-light environments.Specific leaf area（SLA）and stomatal density（SD）increased with reduced light intensity,indicating that plants adapted to low light by expanding their light-capturing area and reducing transpiration.At the same time,specific leaf weight（SLW）,leaf thickness（LT）,palisade tissue thickness（PT）,and spongy tissue thickness（ST）decreased with light intensity,reflecting that plants reduced energy expenditure by thinning leaves and optimized their anatomical structure to enhance light energy capture efficiency.3.With decreasing light intensity,the photosynthetic parameters（C_i,T_r,G_s,P_n）of P.tobira,E.alatus,and L.sinense generally decreased,indicating limited photosynthetic capacity in the shaded environment.In contrast,O.japonicus exhibited higher photosynthetic parameters in moderate low-light environments（T1）,suggesting that it could maximize light energy utilization under moderate shading and showed higher photosynthetic efficiency.4.There were significant differences in the changes of Chl fluorescence parameters among the four plants in the shaded low-light environment.O.japonicus demonstrated the strongest PSII reaction center activity under T1,with significantly enhanced chlorophyll fluorescence parameters(F_v/F_m,F_v’/F_m’,and PIABS),indicating higher light energy capture efficiency and photochemical activity.On the other hand,E.alatus,P.tobira,and L.sinense showed a continuous decrease in these parameters with reduced light intensity,reflecting a significant decline in PSII activity and photochemical efficiency.5.The impact of low-light environments on plant physiological indicators was significant.As light intensity decreased,the Chl a and b content,soluble protein（SP）,malondialdehyde（MDA）,relative electrical conductivity（REC）,superoxide dismutase（SOD）,and peroxidase（POD）activity all increased,while the Chl a/b ratio significantly decreased.Plants enhanced light energy capture efficiency by increasing Chl content and bolstered their antioxidant defense mechanisms through soluble protein accumulation and antioxidant enzyme activity,thus mitigating oxidative damage to cell membranes from low-light stress.6.The overall phenotypic plasticity of the four plants followed this order:O.japonicus>P.tobira>E.alatus>L.sinense.O.japonicus exhibited the strongest plasticity,particularly in photosynthetic efficiency and antioxidant regulation,optimizing light capture and carbon assimilation by increasing chlorophyll and soluble protein content.P.tobira demonstrated high plasticity in photosynthetic features and physiological regulation,adapting to low light by enhancing photosynthesis and antioxidant capacity,and adjusting anatomical structures to improve light utilization.E.alatus showed strong plasticity in chlorophyll accumulation,antioxidant regulation,and leaf area optimization but had limited ability to adjust light energy conversion efficiency.L.sinense exhibited the weakest plasticity,relying mainly on peroxidase activity and leaf thickness adjustment,with poor tolerance to low-light environments.O.japonicus displayed the best adaptation to dynamic low-light environments,with a broad light adaptability range and maintained high photosynthetic efficiency under moderate shading,followed by P.tobira and E.alatus,while L.sinense is unsuitable for growth in such environments.In conclusion,the plasticity of plants is primarily reflected through photosynthetic characteristics and physiological traits.High plasticity in photosynthetic parameters（P_n,T_r,G_s）and physiological indicators（Chla,b,POD,SP）is key for plants to adapt to the dynamic low light environment under viaducts.Therefore,when greening the shaded areas under urban viaducts,it is crucial to fully consider the light environment under the viaduct and the light adaptability range of different plant species.Plants with high photosynthetic and physiological plasticity,such as O.japonicus and E.alatus,should be selected to ensure the optimal growth and development of plants in shaded areas,thereby maximizing the ecological value and benefits of viaduct greening.更多还原