Effect of elevated ozone and carbon dioxide interaction on growth and yield of maize

The effect of elevated tropospheric ozone and carbon dioxide interaction were evaluated on the growth and pro¬ductivity of high quality protein maize (HQPM-1) at the research farm of the Indian Agricultural Research Institute, New Delhi. Maize plants were exposed from emergence to maturity for two years to different ozone levels in non fil¬ter air (NF), charcoal filter air (CF), non-filter air with elevated CO2 (NF+CO2), elevated ozone (EO and EO1), elevated ozone with elevated CO2 (EO+CO2) and ambient control (AC) in open top chambers. Elevated ozone significantly decreased growth attributes of leaf and shoot biomass and leaf area index and the yield attributes. Highest values of all the growth and yield attributes were observed in CF treatment. The photosynthetic rate decreased by 24 to 37% and from 41 to 56% under EO (ambient + 25-35 ppb O3) over NF at tasseling and silking stage respectively. The yield increased by 21 to 31% in the sub ambient ozone levels in the CF treatment over non-filtered control whereas it decreased by 13 and 20 % under EO in both the years respectively. The presence of higher levels of ozone EO1 (ambient + 45-50 ppb O3) however made the plant weak and more susceptible to pest attack, result¬ing in a complete loss in yield. The presence of elevated carbon dioxide along with elevated ozone in the EO+CO2 treatment increased the yield by 9 to 10% over EO alone. Elevated CO2 was able to counter the negative effect of O3 on growth and yield parameters of maize to a certain extent.