Effects of Nitrogen Dioxide on Biochemical Responses in 41 Garden Plants

Nitrogen dioxide (NO2) at a high concentration is among the most common and harmful air pollutants. The present study aimed to explore the physiological responses of plants exposed to NO2. A total of 41 plants were classified into 13 functional groups according to the Angiosperm Phylogeny Group classification system. The plants were exposed to 6 μL/L NO2 in an open-top glass chamber. The physiological parameters (chlorophyll (Chl) content, peroxidase (POD) activity, and soluble protein and malondialdehyde (MDA) concentrations) and leaf mineral ion contents (nitrogen (N+), phosphorus (P+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), manganese (Mn2+), and zinc (Zn2+)) of 41 garden plants were measured. After NO2 exposure, the plants were subsequently transferred to a natural environment for a 30-d recovery to determine whether they could recover naturally and resume normal growth. The results showed that NO2 polluted the plants and that NO2 exposure affected leaf Chl contents in most functional groups. Increases in both POD activity and soluble protein and MDA concentrations as well as changes in mineral ion concentrations could act as signals for inducing defense responses. Furthermore, antioxidant status played an important role in plant protection against NO2-induced oxidative damage. NO2 poses a pollution risk to plant systems, and antioxidant status plays an important role in plant protection against NO2-induced oxidative damage. In conditions of strong air pollution, more evergreen plants may be considered in landscape design, particularly in seasonal regions. The results of this study may provide useful data for the selection of landscaping plants in NO2 polluted areas