Atmospheric Particle Retention Capacity And Physiological Responses Of Nerium Indicum Mill. Under Secondary PM_2.5Pollution

To explore the effects of secondary PM pollution on the pm-retention capacity of typical urban greenbelt plants and their physiological responses,in this study,the evergreen shrub oleander(Nerium indicum Mill.)commonly used in the southern cities was used as the tested species.Our study is based on the controlled experiment,the vehicle exhaust gas was used to simulate the particulate matter pollution source,and the open-top chamber method was used to treat the tested samples for 12 weeks.The season1 was 4 weeks,the recovery period was 4 weeks,and the season2was 4 weeks.The PM2.5 concentration during the average air pollution period was around 613.72±44.85 ?g·m-3.We sampled each week to determine the retention ability of different sizes of pm and physiological and biochemical response during the two seansons of same group of oleanders exposure under polluted and normal conditions,and use the APTI index to assess the air pollution tolerance of plants.The result shows:(1)Under the condition of secondary particulate matter pollution,the total dust retention of the saturated unit leaf area of oleander decreased by 12.95%,the proportion of coarse particulate matter decreased the most,and the time of saturated ash retention of oleander during the second stress period was delayed.8-9 days;(2)For the first time,the effects of particulate matter pollution on plant physiological and biochemical characteristics occurred 14 days before stress,the pigment content of leaves decreased by 18.7%,the activity of antioxidant enzymes increased by 15.77%,and the content of ascorbic acid and specific leaf weight increased by 18.11.%and 9.65%;(3)The degradation of oleander pigment content was weakened under the condition of secondary particulate matter pollution.The specific leaf leaf weight level of leaves was 8.06%higher than that of the first particulate matter pollution,and the response of antioxidant enzyme activity and ascorbic acid content and dust retention was weakened.(4)The APTI of the plants under the secondary particulate matter showed an upward trend,indicating that the air pollution resistance of the plants showed an increase,but the difference of the plant responses before and after the APTI numerical comparison was not found(the APTI difference between the nodes at the same time)Both are p>0.05);(5)The dark respiration rate of plants under the condition of the first particulate matter pollution was significantly higher than that of the control group(p<0.01).The difference of dark respiration rate between the treatment group and the control group under the secondary pollution condition still existed,but the overall significant decrease(p=0.057).