Particulate Retention And Physiological Response Of Three Evergreen Broad-leaved Afforestation Tree Species In Yangtze River Delta

This paper studies the dynamics of particulate matter deposition and physiological response mechanisms of the evergreen broad-leaved afforestation tree species in Yangtze river delta based on controlled experiments,including Euonymus Japonicus,Pittosporum tobira and Photinia serrulata.Selecting tree species with strong dust-retention abilities and high stress tolerance to provide a certain theoretical basis for scientific allocation of urban green landscape and improvement of air quality.In spring,the maximum retention of total particulate matter of Euonymus japonicus and Pittosporum tobira was 188.47±3.72?g·cm-2 and 80.70±1.38?g·cm-2,respectively.The retention of particles with different particle sizes per unit area of Euonymus japonicus was higher than that of Pittosporum tobira.In the summer,the dust retention capacity is Euonymus japonicus,Photinia serrulata and Pittosporum tobira in descending order,Among them,the maximum retention of total particles of Euonymus japonicus,Photinia serrulata,and Pittosporum tobira was 152.45±11.47?g·cm-2,66.70±4.31?g·cm-2,87.71±5.99?g·cm-2,respectively.The dust-retention capacity of Euonymus japonicus and Pittosporum tobira in spring was significantly higher than that in summer,but the difference of ability of Euonymus japonicus was even more significant in seasonal.When the plants were exposed to particulate stress,the net photosynthetic rate of the three plants decreased significantly.The percentages of the decrease in the contents of the soluble sugar contents were higher in Euonymus japonicus,Photinia serrulata,Pittosporum tobira.The superoxide dismutase(SOD)and peroxidase(POD)activities of Euonymus Japonicus,Photinia serrulata,Pittosporum tobira both showed a trend of increasing first and then decreasing,and POD played a more important protective role than SOD.With the increase of dust-retention time,intracellular free radicals gradually accumulated,induced or exacerbated membrane lipid peroxidation,and the malondialdehyde(MDA)content of plants increased significantly.The degree of cell membrane lipid peroxidation was: Photinia serrulata > Pittosporum tobira > Euonymus japonicus.The MDA content and SOD and POD activities of the three plants all peaked on the 12 th day of dust retention,indicating that the plants were most damaged.To sum up,the order of the resistance of the three plants to car exhaust is: Euonymus japonicus > Photinia serrulata > Pittosporum tobira.