Role of soil nitrogen amendments in management of ozone stress in plants: a study of the mechanistic approach

In view of the increasing concentration of tropospheric ozone (O3), it becomes important to develop mitigative measures which help in sustaining plant yield. On the basis of a few experiments, soil nitrogen amendments have given some promising results and can be used in the partial amelioration of O3 stress in plants. The aim of the present experiment was to evaluate the interactive effects of ambient O3 and nitrogen treatments on selected physiological, biochemical and morphological characteristics of palak (Beta vulgaris L. var Allgreen) plants. The experimental design consisted of three nitrogen treatments i.e, control (no supplement nitrogen), recommended dose (N1) and 1.5 x recommended dose (N2). The results of the experiment showed that the mechanisms through which nitrogen amendments assisted the plants to cope with O3 stress were dominated by the physiological features like stomatal conductance at low nitrogen dose treatment, while at higher nitrogen dose treatment, biochemical characteristics are more prominent. Alteration in the enzymatic and non-enzymatic antioxidants in nitrogen treated plants as compared to control, clearly suggest a reduction in O3 stress upon nitrogen amendments. The biomass allocation pattern is also modified by nitrogen treatments to sustain a higher yield. The positive effect of biomass allocation was more prominent in N2 plants where yield increments were higher. The yield increments, as compared to control were higher in N2 as compared to N1, indicating that a higher nitrogen dose was more effective in partial amelioration of O3 stress. However, more experiments are required to be planned to determine the exact dose of nitrogen amendments needed for different plants.