Urban shading is caused by arti fi cial urban construction and has different effects on the photosynthesis of plant, and this shading will affect the plants in photosynthesis. The purpose of the study was to reveal the plant photo- synthetic characteristics in urbanshading,provide theoreticalbasis for improving the ecologicalbene fi tsof urban vegetation and provide scienti fi c basis for urban plant landscape con fi guration. We selected leaf samples of Eu- onymus fortunei from three typical urban light environments: full natural light, part-time shade and full urban building shade. We quanti fi ed various measures of photosynthesis and chlorophyll fl uorescence using the CIRAS-2 photosynthesis and FMS-2 fl uorescence systems, respectively. The results indicated that urban shading by arti fi cial structures caused differences in both the spatial and temporal distribution of photosynthetic active radiation ( PAR ). Surprisingly, this was not due to differences to the air temperature ( Ta ), relative humidity and CO 2 concentrations, whichwereconsistent amongthelightconditions. Urbanbuilding shade alsocausedchanges in leaf morphology and chloroplast pigment content of E. fortunei .Leafarea( LA ) increased with part-time shade and decreased with full shade, while lamina mass per unit area ( LMA ) decreased signi fi cantly as the shade in- creased. Chlorophyll b content increased and the chlorophyll a / b ratio decreased with the decrease of PAR . Pn of E. fortunei displayed an irregular single-peak curve under full light and part-time shade, and the peak for each ap- peared at10:00 and 12:00, respectively. Pn displayed a double-peak curve under full shade, with peaks appearing at 10:00 and 16:00. Tr of E. fortunei was signi fi cantly correlated with Pn .The Pn-PAR curve showed that Pmax , LSP , LCP ,and Rd all decreased along with PAR , with the exception of AQY , which signi fi cantly increased. Chlorophyll fl uorescence parameters also changed under the different light environments. Fo and Φ PS II both increased with the decreases in PAR ,but Fv / Fm and NPQ decreased. Different levels of urban shading caused the changes in adaptive strategies of E. fortunei . When there was no direct sunlight appearing, a highest level of shading, E. fortunei presented obvious adaptive changes in its physiological photosynthetic processes, morphology, photo- synthetic pigments and so on, and this type of the greatest shading caused by urban buildings or other infrastruc- tures can obviously affect the growth of plants.
