Influence of night-time light pollution on the photosynthesis and physiological characteristics of the urban plants Euonymus japonicus and Rosa hybrida

Background Night-time light pollution (NLP), which breaks the natural cycle of day and night, has become a new threat to urban ecosystems. Plants are the main component of urban ecosystems and play an irreplaceable role in maintaining urban ecological balance. The effects of NLP with various radiation sources, including green, white, blue and red light provided by light-emitting diodes, on urban plants, Euonymus japonicus and Rosa hybrida , were examined in a block field experiment. Results NLP caused photoinhibition and oxidative stress in plants, and the extent of the deleterious effects varied with the spectral distribution of artificial light sources and species. Both E. japonicus and R. hybrida were more sensitive to blue and red light, which reduced the pigment concentration, net photosynthetic rate, stomatal limit value, effective quantum yield, apparent electron transfer rate and photochemical quenching coefficient, and markedly increased the malondialdehyde content and total antioxidant capacity. However, those negative effects under white light were only present in E. japonicus and not in R. hybrida . Furthermore, blue and red light significantly decreased the stomatal conductance of E. japonicus . In contrast, green light had no significant effect on the above indices for both species. All spectra did not significantly change the sugars and starch contents for either species. Conclusions Considering that the spectral distribution of artificial light at night in cities has great heterogeneity and that its effect varies with plant species, it is important to arrange tree species with NLP tolerance and install appropriate light sources in urban areas based on the corresponding physiological responses and adaptation of urban trees.