Ozone

Ozone (O3) is not only affecting plants through toxicity, it can also affect plants by acting as green house gas. It is important to note that ozone has been rated the third most important anthropogenic green house gas after carbon dioxide and methane. The increasing emissions of reactive hydrocarbons and NO2 in the urban areas have significantly increased the ground level O3 concentrations and affects plants in agricultural, forest and remote rural areas. A seasonal variation in O3 showed a pronounced maximum (62 ppb in March) in summer with values sometime exceeding 90 ppb and a minimum in the monsoon and post monsoon season (17 ppb in August). Further, low rainfall, high temperature and solar radiation have given rise to the gradual build up of O3 during summer and winter. Regional pollution is shown to have maximum contribution to O3 level during February to May in high altitude region of Nilgiris (Udayasoorian et al., 2013).