نوع مقاله : علمی- پژوهشی
نویسندگان
1 استادیار، گروه علوم و فناوریهای زیستی، واحد یادگار امام خمینی (ره) شهرری، دانشگاه آزاد اسلامی، تهران، ایران
2 نویسنده مسئول، دانشیار، گروه علوم و فناوریهای زیستی، واحد یادگار امام خمینی (ره) شهرری، دانشگاه آزاد اسلامی، تهران، ایران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Background and Objectives: Trees in urban environments improve air quality by filtering and absorbing gases and particles. However, these trees may themselves be vulnerable to air pollution. Oriental plane trees (Platanus orientalis L.) were widely used for Tehran's greenery, Iran, but are now gradually deteriorating. Black locust (Robinia pseudoacacia L.), a resistant species adaptable to various climates, is often planted for beautifying green spaces. This study examined physiological leaf characteristics of both species in late spring across three Tehran areas with varying air pollution levels to assess oriental plane sensitivity and black locust resistance.
Methodology: Twenty leaves from five trees of each species were collected from three parks: Sadra (District 22), Al-Mahdi (District 9), and Avesta (District 11), spanning western to central Tehran. Based on Tehran Air Quality Control Organization data, Al-Mahdi and Avesta parks were classified as polluted, while Sadra Park was relatively clean. Stomatal conductance (transpiration), stomatal resistance, and relative leaf moisture were measured using a porometer. Chlorophyll and carotenoid contents were determined via the Porra (2002) method, and anthocyanin levels via Mancinelli et al. (1988). Dried leaves and soil samples were extracted using a Digesdahl apparatus per Pichtel and Bradway (2008). Iron, zinc, nickel, and copper concentrations in extracts were analyzed using an ICP atomic absorption spectrometer. The experiment followed a completely randomized design with five replicates; SAS software (version 9.1) was used for analysis, with two-way ANOVA and Duncan's multiple range test for variance and mean comparisons.
Results: Soil from the three areas showed minor textural differences, with heavy metal levels below permissible limits. Both species exhibited highest stomatal transpiration in polluted areas and lowest in Sadra Park. Stomatal resistance was highest in Sadra Park for both species, though oriental plane leaf moisture showed no significant differences across areas. Black locust leaf moisture was lowest in Sadra Park (P<0.01). Chlorophyll and carotenoid levels were highest in Sadra Park for oriental plane (P<0.01) and black locust (not significant). Anthocyanin was highest in oriental plane leaves from Sadra Park (P<0.01) and lowest in black locust leaves from Sadra Park (P<0.05). Air pollution did not significantly affect iron, zinc, nickel, or copper in oriental plane leaves, which contained higher zinc and nickel than black locust. Black locust leaves had higher iron and copper, with iron elevated in polluted areas (P<0.01). Nickel was lowest in black locust leaves from Al-Mahdi Park (P<0.05), while copper and zinc showed no significant differences across areas.
Conclusion: Unlike oriental plane trees, black locust trees showed no air pollution effects on chlorophyll and carotenoid content through late spring. Black locust may defend against pollution by increasing leaf anthocyanin. Air pollution increased stomatal conductance in both species, but black locust prevented dehydration by reducing stomatal resistance and maintaining leaf moisture, while oriental plane did not, resulting in necrosis and leaf dryness, especially in high-pollution traffic zones.
Keywords: Air pollution, green space, heavy metals, physiological traits, plant resistance.
کلیدواژهها [English]
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