Laboratory of Air Pollution and Global Climate Change, Department of Botany, Banaras Hindu University, Varanasi 221005, India; Laboratory of Air Pollution and Global Climate Change, Department of Botany, Institute of Science, Banaras Hindu University, Varanasi 221005, India.
Laboratory of Air Pollution and Global Climate Change, Department of Botany, Banaras Hindu University, Varanasi 221005, India; Laboratory of Air Pollution and Global Climate Change, Department of Botany, Institute of Science, Banaras Hindu University, Varanasi 221005, India.
Sci Total Environ. 2020 Mar 25;710:136363. doi: 10.1016/j.scitotenv.2019.136363. Epub 2019 Dec 31.
Air pollution in an urban environment is the major stress factor for vegetation due to the direct generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). To quantify urban air pollution-induced ROS/RNS formation, damage and detoxification, nine different biochemical parameters related to free radical formation, scavenging and membrane damage were estimated in twelve tropical tree species. The experiment was performed in three different seasons at four distinct urban environments in Varanasi city located in the Indo-Gangetic plain of India. Redundancy analysis was performed to statistically assess the relationship between air pollutants (PM, NO, SO and O) and temperature with ROS/RNS generation and their detoxification. Significant effects of air pollution exposure and temperature on ROS/RNS formation, scavenging and membrane damage were recorded with increasing pollution load in the city for all the tree species. The extent of variability (47-87%) in responses of different tree species was due to their intrinsic ability to scavenge free radicals which minimized the membrane damage. PM, NO and O were identified as major pollutants that influenced trees to different extents in regulating ROS/RNS. However, the response was maximum against NO (34-72%) followed by PM (16-64%) and O (3-31%), indicating that under urban environment, trees are considerably sensitive to the combined effects of both particulate and gaseous pollutants. Reactive oxygen intermediate release, total free radical scavenging activity, NO scavenging activity and membrane stability index were identified as major parameters which showed distinct responses with increasing pollution load. Caesalpinia sappan, Ficus religiosa and Albizia lebbeck were identified as most tolerant tree species having higher ROS/RNS scavenging potential resulted in lower membrane damage. Thus responses of urban trees to air pollution are governed by their intrinsic defence mechanisms to scavenge ROS/RNS by maintaining the membrane integrity through integrated cross-talk between different antioxidative pathways.
城市环境中的空气污染是植被的主要应激因素，因为它会直接产生活性氧（ROS）和活性氮（RNS）。为了量化城市空气污染诱导的 ROS/RNS 形成、损伤和解毒，在 12 种热带树种中估计了与自由基形成、清除和膜损伤相关的 9 种不同的生化参数。该实验在印度恒河平原的瓦拉纳西市的四个不同城市环境中的三个不同季节进行。冗余分析用于统计评估空气污染物（PM、NO、SO 和 O）和温度与 ROS/RNS 生成及其解毒之间的关系。随着城市污染负荷的增加，所有树种的空气污染物暴露和温度对 ROS/RNS 形成、清除和膜损伤都有显著影响。不同树种对不同空气污染物的响应程度差异很大（47-87%），这是由于它们内在的清除自由基的能力，从而最小化了膜损伤。PM、NO 和 O 被确定为主要污染物，它们以不同的程度影响树木调节 ROS/RNS。然而，NO 的影响最大（34-72%），其次是 PM（16-64%）和 O（3-31%），这表明在城市环境下，树木对颗粒状和气态污染物的综合影响相当敏感。活性氧中间产物释放、总自由基清除活性、NO 清除活性和膜稳定性指数被确定为主要参数，随着污染负荷的增加，这些参数表现出明显的响应。苏木、菩提树和印度苦楝被确定为最耐受树种，它们具有更高的 ROS/RNS 清除潜力，导致较低的膜损伤。因此，城市树木对空气污染的反应受其内在防御机制的控制，这些机制通过不同抗氧化途径之间的综合相互作用来清除 ROS/RNS，从而维持膜的完整性。
