Comparison of DNA damage detected by plant comet assay in roadside and non-roadside environments

Although mixed air pollutants generated from traffic are suspected as one of the causes of DNA damage in living species, effects of the combination of these pollutants and other micro-environmental factors on urban biota have not been clarified yet. Thus, this study mainly aimed to detect the genetic damages in selected plant biomonitors, which were ginkgo (Ginkgo biloba), pohtos (Epipremnum aureum), and periwinkle (Vinca rosea), setting in roadside and non-roadside environments. Two monitoring positions were selected in the Hongo campus of the University of Tokyo, Japan. This area was categorized as the urban residential zone. Both roadside and non-roadside samples were analyzed by using comet assay protocol. Different distribution changes in DNA migration ratios of all species could be observed and further interpreted as percentages of DNA damage. For all test species, in the final stage of experiment, roadside samples showed significantly higher degrees of DNA damage than non-roadside one. Time-dependent response pattern of each species to the overall environmental stresses was performed. Increase in the percentages of DNA damage could be expressed by regression equations. In addition, ratio of percentage of DNA damage between roadside and non-roadside species (R/N ratio) was introduced in order to clarify the additional genetic effect caused by roadside air pollutants. Series of response phase of plant under stresses, including cell destabilization, damage intensification, and re-stabilization, were explained. This study might be applied as a preliminary method in urban air quality assessment for detecting the existing effects of air pollutants and micro-environmental stress in an urban ecosystem.