Impact of tropospheric ozone on wheat (Triticum aestivum L.) in the eastern Gangetic plains of India as assessed by ethylenediurea (EDU) application during different developmental stages

Phytotoxic ambient O3 concentrations are often recorded at several rural sites supporting agriculture in India. As ethylenediurea (EDU) has been successfully used to prevent foliar O3 injury and to determine O3 effects on growth and yield of plants, the present study was conducted to standardize the optimal dose of EDU in providing maximum protection against O3 impact on wheat (Triticum aestivum L. cv. HUW468) under natural field conditions at a sub-urban site of Varanasi, India. Optimal dose of EDU (400 ppm) was also supplied at different growth stages to assess the usefulness of application in providing protection against O3. Air monitoring conducted for 12 h showed high concentrations of O3 varying from 27.7 to 59.1 ppb from December 2007 to April 2008. Root and shoot lengths, number of leaves, leaf area, total biomass and total chlorophyll and carotenoid contents were higher in EDU-treated plants as compared to untreated ones. Various yield attributes also improved under EDU application suggesting its protective nature against ozone. The results clearly suggest that 400 ppm EDU was most effective in alleviating the negative effect of O3 on wheat and its application throughout the plant life is most beneficial for protection against O3 compared to particular growth stage.