AIr Pollution and Its Impact on Plant Physiological and Biochemical Responses: A Review

Air pollution has emerged as a major driver of ecosystem degradation, agricultural yield reduction, and climate–biosphere interactions. Rapid industrialization, urban expansion, fossil fuel combustion, and intensive agriculture have substantially increased atmospheric concentrations of particulate matter (PM), nitrogen oxides (NOx), sulphur dioxide (SO2), ozone (O3), volatile organic compounds (VOCs), heavy metals, and persistent organic pollutants. These contaminants enter plant tissues primarily through stomatal uptake and surface deposition, triggering excessive production of reactive oxygen species (ROS) and disrupting cellular redox balance. Tropospheric ozone is particularly phytotoxic, impairing photosystem function, Rubisco activity, and carbon assimilation, while particulate deposition reduces light interception and promotes toxic metal accumulation. Pollutant-induced oxidative stress damages membrane lipids, proteins, nucleic acids, and chloroplast structures, leading to reduced photosynthetic efficiency, premature senescence, altered phenology, and significant yield losses. Plants activate coordinated defence responses involving antioxidant enzymes, non-enzymatic antioxidants, transcription factors, MAPK signalling cascades, and hormone-mediated regulatory networks; Prolonged exposure frequently overwhelms protective capacity. Interactions between air pollution and climate change–associated stresses such as drought and heat further intensify physiological disruption and limit crop resilience. Integrated mitigation strategies—including emission reduction, green infrastructure development, and advancement of pollution-tolerant crop varieties through molecular and genomic approaches- are essential to safeguard ecosystem stability and global food security under accelerating environmental change.