Application of ethylene diurea (EDU) in assessing the response of a tropical soybean cultivar to ambient O3: Nitrogen metabolism, antioxidants, reproductive development and yield

•EDU maintained reproductive sites in soybean cultivar under ambient O3.•Level of protection by EDU to plant depends upon O3 concentration at different developmental stages.•Identification of mode of action of EDU with respect to antioxidative defense mechanism, N metabolism and metabolites in soybean at flowering stage.

The present study deals with assessment of response of a tropical soybean cultivar to O3 in relation to photosynthetic pigments, chlorophyll fluorescence kinetics, antioxidative capacity, N assimilation enzymes, metabolites, growth and yield using ethylene diurea (EDU) given as a soil drench (400) ppm at an interval of 10 days after germination up to maturity. Mean O3 concentration was 42 ppb and accumulated threshold above 40 ppb (AOT 40) was 9.07 ppm h. Lipid peroxidation and total phenolics reduced, while increases in activities of antioxidative and nitrogen assimilation enzymes, ascorbic acid, protein, photosynthetic pigments, Fv/Fm ratio, number of leaves, flowers, pods, branches and yield attributes were found in EDU treated plants. EDU alleviated the negative effects of O3 by enhancing the first line of defense against ROS and protecting N assimilation enzymes at flowering and maintaining adequate supply of photosynthates to developing pods during pod filling stage. EDU provided maximum protection between flowering to pod filling stage.