Photosynthetic Pigments as Parameters/Indicators of Tree Tolerance to Urban Environment (Plovdiv, Bulgaria)

As polluted air is a stress factor that contributes to the decline of trees in urban areas, we aimed to investigate the complex impact of anthropogenic activity on chlorophylls and carotenoids content of four tree species (Acer heldreichii Boiss., Tilia tomentosa Moench, Fraxinus excelsior L. and Pinus nigra L.). Seedlings were purchased from certified greenery and planted by us at four selected sites in the city of Plovdiv (Bulgaria) during spring of 2015. Leaf samples were taken monthly and photosynthetic pigments content was measured immediately after sampling. Results of this preliminary study confirmed that pigment levels in plants varied between species, locations and seasons. Although an extension to the above work is necessary to quantify possible differences between the levels at which photosynthetic components are affected, it is obvious that both ratios chlorophyll a/b and chlorophylls/carotenoids could serve as very useful indicators of stress level. Because of the non-specificity in pigment reaction to different type of anthropogenic impact, we recommended to apply a combination among pigments concentration and another parameters (morphological, biochemical, physiological) for the targets of biomonitoring.