EFFECT OF AIR POLLUTION ON LEAF MORPHOLOGY AND STOMATAL CHARACTERISTICS OF SELECTED PLANT SPECIES IN URBAN AREAS OF MANSEHRA DISTRICT

Abstract

Urban air pollution can substantially alter plant morphology and stomatal characteristics, making vegetation a useful indicator of environmental stress. The present study evaluated the effects of different pollution levels on five common plant species, namely Platanus orientalis, Populus ciliata, Morus alba, Melia azedarach, and Dalbergia sissoo, in urban areas of Mansehra District, Khyber Pakhtunkhwa, Pakistan. Leaf length, width, area, petiole length, fresh and dry mass, visible leaf injury, stomatal density, stomatal dimensions, and stomatal index were assessed under low, moderate, and high pollution conditions. Leaf area decreased markedly under high pollution, with the greatest reductions recorded in Populus ciliata (29.7%) and Morus alba (28.3%), whereas Melia azedarach showed the smallest reduction (14.9%). Visible leaf injury increased from 3.9–6.4% at low-pollution sites to 18.5–34.8% at highly polluted sites. Mean stomatal density declined from 209.0 ± 23.3 mm⁻² under low pollution to 158.0 ± 11.0 mm⁻² under high pollution, accompanied by reductions in stomatal length, width, and index. Two-way ANOVA showed significant effects of pollution and species on all measured traits (p < 0.001). Overall, the findings demonstrate species-specific sensitivity to urban air pollution and highlight the potential of leaf and stomatal traits for biomonitoring environmental pollution in Mansehra District.