Consequences of Artificial Light at Night (ALAN) on Urban Tree Functioning: A Case Study

Plants use light as a source of both energy and signalling. Street lighting is integral to urban infrastructure, providing safety and visibility during night hours. However, the widespread use of artificial lighting in urban areas has raised concerns about its potential impact on the physiological functioning of urban plants. This study aimed to understand the physiological responses of tree species at the seedling stage under exposure to artificial light at night (ALAN) provided by 50-W LEDs. The findings revealed that ALAN significantly affected chlorophyll content, stomatal conductance, transpiration, air and leaf temperature, leaf area, and soil moisture. All measured physiological functional traits declined under ALAN exposure compared to control plants. Further, long-term studies are recommended to draw comprehensive conclusions that will assist urban planners and policymakers in designing landscapes for developing green spaces in urban areas.