Effects of dust pollution on leaf morphology and chlorophyll content: A comparative study across two seasons in Biratnagar, Nepal

The effect of dust on leaf morphology and chlorophyll content in industrial, roadside, residential, and campus areas during the winter (January) and monsoon (June) season of 2024 was investigated. The highest dust load on the leaves of Tectona grandis was recorded in industrial areas during the winter season. The greatest leaf area reduction was observed in Azadirachta indica (13.25%) in winter and Citrus maxima (14.32%) in the monsoon season. The specific leaf area (SLA) of Ficus religiosa decreased by 20.48% in winter, and that of Nephelium litchi decreased by 28.46% in monsoon, particularly in industrial areas, likely due to their dust-trapping capacity and stress tolerance. Total chlorophyll was mostly reduced in polluted areas (industrial, roadside areas) in the winter season. During the studied seasons, chlorophyll-a ranged from 0.04 to 2.56 mg/g, chlorophyll-b ranged from 0.66 to 2.56 mg/g, and total chlorophyll ranged from 0.13 to 3.08 mg/g. Both chlorophyll-a and chlorophyll-b showed greater reduction during the monsoon season compared to winter. Less reduction in chlorophyll-a was observed in Ficus benghalensis, Ficus religiosa, Mangifera indica, Neolamarckia cadamba, and Syzygium cumini. But the species like Artocarpus heterophyllus, Citrus maxima, Syzygium cumini, and Mangifera indica exhibited less reduction in chlorophyll-b. The chlorophyll a:b ratio was generally higher during the winter season, particularly in the campus area (a less polluted site), whereas the ratio was reduced in more polluted areas. Physiological characteristics were more affected by dust accumulation than morphological characteristics. Plant species like Artocarpus heterophyllus, Ficus benghalensis, Ficus religiosa, Mangifera indica, Neolamarckia cadamba, Nephelium litchi and Psidium guajava showed comparatively less impact from dust, indicating their potential use in minimizing air pollution and enhancing urban green spaces.