Role of nitrogen amendments on carbon fixation efficiency of ozone exposed lemongrass: Interrelationship between secondary metabolite production and yield

The phytotoxic nature of Ozone (O₃) has been well documented in a number of scientific literatures during the last few decades. Although there are sufficient studies related to O₃ impact assessment studies on crop plants and tree species, studies pertaining to O₃ effects on medicinal plants are comparatively sparse. During the recent years, the mitigation strategies for management of O₃ stress in plants have also assumed paramount significance. The present study sought to explore the combined impact of soil nitrogen (N) amendments and O₃ doses on morphological and physiological responses, and metabolite profile of lemongrass, an aromatic medicinal plant. The experiment utilised three levels of inorganic soil N amendments within Open Top Chambers, subjected to ambient (A) and two elevated O₃ doses. For each O₃ treatment, control was also maintained, wherein no N amendments were done. The objective of the study was to study the pattern of allocation of carbon pool towards biomass accumulation and secondary metabolite production under N amendments and O₃ exposure conditions in lemongrass. The results of the physiological traits clearly suggest the resurgence of the photosynthetic machinery of O₃ exposed lemongrass. The improved response of the carbon fixation processes upon N amendments resulted in supplemented carbon pool, diverting it towards increased biomass accumulation and yield of lemongrass, which was depreciated under O₃ stress. This study demonstrates that N amendments in O₃ stressed lemongrass enhance bioactive compound production, and sustain yield. Further researches are required to establish optimal N doses under varying O₃ conditions, potentially advancing pharmaceutical applications of O₃ exposed medicinal plants.