Negative impacts of elevated ozone on dominant species of semi-natural grassland vegetation in Indo-Gangetic plain.

Increasing tropospheric ozone (O3) concentrations in most regions of the world have led to significant phytotoxicity to all types of vegetation. Indo-Gangetic Plains of India is one of the hot spot areas with high O3 concentrations throughout the year although O3 phytotoxicity on grassland species in this region is not explored. Therefore the present study was conducted to assess the responses of a dominant species, Ischaemum rugosum Salisb, a C4 grass and a co-dominant species Malvastrum coromandelianum (L.) Garcke, a C3 forb under future elevated O3 (non filtered ambient + 20 nl l-1; NFA+) concentration compared to non filtered ambient (NFA; 48.7 nl l-1, 8 h mean) for 9 weeks from 15th May to 15th July 2016 in mix-culture using open-top chambers (OTCs). Plants were assessed for physiological, biochemical and growth parameters including biomass accumulation during vegetative and reproductive stages to assess the O3 induced responses. Under NFA+, higher reductions were observed in physiological parameters, growth and total biomass accumulation in M. coromandelianum compared to I. rugosum while both the species suffered membrane damage. Enhancement in contents of ascorbic acid and tannin in I. rugosum while proline and total phenolics in M. coromandelianum led to more protection of former species compared to later from oxidative damage. No significant change in stomatal conductance in I. rugosum while significant increase in M. coromandelianum might have led to more accumulation of O3 inside the plant, thus more negatively affecting the performance of later species. The present study concludes that M. coromandelianum (C3 photosynthetic pathway) will be relatively more negatively affected compared to I. rugosum (C4 photosynthetic pathway) under future O3 concentrations.