The present experiment was done on two different cultivars of a tropical legume, Cymopsis tetragonoloba L. Taub. (cluster bean) cvv. Pusa-Naubahar (PUSA-N) and Selection-151 (S-151). The experiment was conducted under ambient ozone (O3) conditions with inputs of three different doses of inorganic nitrogen (N1, recommended; N2, 1.5-times recommended and N3, 2-times recommended) as well as control plants. The objective of this study was to evaluate the effectiveness of soil nitrogen amendments in management of ambient ozone stress in the two cultivars of C. tetragonoloba. Our experiment showed that nitrogen amendments can be an efficient measure to manage O3 injury in plants. Stimulation of antioxidant enzyme activities under nitrogen amendments is an important feature of plants that help plants cope with ambient O3 stress. Nitrogen amendments strengthened the antioxidant machinery in a more effective way in the tolerant cultivar PUSA-N, while in the sensitive cultivar S-151, avoidance strategy marked by more reduction in stomatal conductance was more prominent. Enzymes of the Halliwell–Asada pathway, especially ascorbate peroxidase and glutathione reductase, were more responsive and synchronised in PUSA-N than S-151, under similar nitrogen amendment regimes and were responsible for the differential sensitivities of the two cultivars of C. tetragonoloba. The present study shows that 1.5-times recommended dose of soil nitrogen amendments was sufficient in partial mitigation of O3 injury and the higher nitrogen dose (2-times recommended, in our case), did not provide any extra advantage to the plant’s metabolism compared with plants treated with the lower nitrogen dose (1.5-times recommended).

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In view of the present climate change scenario which significantly affects the agricultural sustainability, we need to develop certain strategies that help us to sustain agricultural productivity. Ground level ozone is an important component of climate change that has been proved to be the main culprit causing significant agricultural losses during the past few decades. The aim of present study is to evaluate the effectiveness of nutrient treatment in sustaining agricultural production under ambient ozone stress. Two varieties of maize (Zea mays L. var Malviya hybrid-2 and HHM-1) were taken as the experimental plants. Three doses of nutrients (NPK) recommended (N1), 1.5x recommended (N2) and 2x recommended (N3) were applied to the experimental plants grown under ambient ozone stress. Daytime eight hourly ozone concentrations varied from 49.2 to 59 ppb during the experimental period. Plants treated with nutrients responded better than the plants without nutrient, which served as control. Yield (test weight) increased significantly by 11, 46 and 44 % in Malviya hybrid-2 and by 11, 18 and 18.3 % in HHM-1 at N1, N2 and N3 treatments, respectively, as compared to control. Variations in the biomass allocation strategies during the vegetative and reproductive phases resulted in higher yield increments in Malviya hybrid-2 as compared to HHM-1. It was further observed that N2 treatment was sufficient to cause significant increments in yield as compared to control. The results of the present experiment clearly suggest that nutrient amendments can be effectively used in partially mitigating ambient ozone stress and sustaining agricultural productivity to some extent. However, more experimentation with different crop varieties is required to prove the expediency of nutrient amendments.

The present study was conducted to assess the effect of elevated ozone stress on the development and metabolite contents of lemongrass, a medicinal plant. The experimental plant was exposed to two elevated ozone concentrations (ambient + 15 ppb, and ambient + 30 ppb) using open-top chambers. Samplings were carried out at 45 and 90 days after transplantation (DAT), for the analysis of different characteristics, while the metabolite contents of leaves and essential oils were analyzed at 110 DAT. Both the doses of elevated ozone had notable negative effects on the carbon fixation efficiency of plants, resulting in a significant reduction in plant biomass. Enzymatic antioxidant activity increased during the second sampling, which suggests that the scavenging of reactive oxygen species was more prominent in lemongrass during the later developmental stage. The results of the present study showed a stimulated diversion of resources towards the phenylpropanoid pathway, which is made evident by the increase in the number and contents of metabolites in foliar extract and essential oils of plants grown at elevated ozone doses, as compared to ambient ozone. Elevated ozone not only upregulated the contents of medicinally important components of lemongrass, it also induced the formation of some pharmaceutically active bio compounds. On the basis of this study, it is expected that increasing ozone concentrations in near future will enhance the medicinal value of lemongrass. However, more experiments are required to validate these findings.

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