Sensitivity of agricultural crops to tropospheric ozone: a review of Indian researches.

Tropospheric ozone (O) is a long-range transboundary secondary air pollutant, causing significant damage to agricultural crops worldwide. There are substantial spatial variations in O concentration in different areas of India due to seasonal and geographical variations. The Indo-Gangetic Plain (IGP) region is one of the most crop productive and air-polluted regions in India. The concentration of tropospheric O over the IGP is increasing by 6-7.2% per decade. The annual trend of increase is 0.4 ± 0.25% year over the Northeastern IGP. High O concentrations were reported during the summer, while they were at their minimum during the monsoon months. To explore future potential impacts of O on major crop plants, the responses of different crops grown under ambient and elevated O concentrations were compared. The studies clearly showed that O is an important stress factor, negatively affecting the yield of crops. In this review, we have discussed yield losses in agricultural crops due to rising O pollution and variations in O sensitivity among cultivars and species. The use of ethylene diurea (EDU) as a research tool in assessing the losses in yield under ambient and elevated O levels also discussed. Besides, an overview of interactive effects of O and nitrogen on crop productivity has been included. Several recommendations are made for future research and policy development on rising concentration of O in India.