Development of Resistance in Two Wheat Cultivars Against Constant Fumigation of Ozone

Tropospheric ozone (O 3 ) has been recognized as the major threat for worldwide agriculture and wheat production will have a crucial bearing on food security in the coming decades. The present study was conducted to evaluate the response of two wheat cultivars (HUW 234 and HP 1209) at constant levels of elevated O 3 and to compare results of the present open top chamber studies (OTC) with free air concentration studies (FACE). Wheat cultivars were exposed to 70 (T 1 ) and 100 (T 2 ) ppb O 3 for 4 h daily from germination to maturity. Both the cultivars showed differential and negative responses on photosynthetic pigments, morphological characteristics and total biomass at different stages of sampling. Photosynthetic rate, stomatal conductance and photosynthetic efficiency were negatively affected by the exposure of O 3 in both the cultivars. Allocation of biomass in different components of plants was observed to be diverse amongst the cultivars under different treatments resulted into the varied responses yield attributes. Exposure of O 3 causes variation in quantity as well as quality of grains of both the cultivars with higher yield reduction in HP1209. Therefore, the findings of the experiments revealed that the continuous O 3 exposure developed compensatory mechanism particularly reduced stomatal conductance, altered allocation pattern managed to maintain yield against O 3 , hence led to less reductions in yield was recorded as compared to OTCs and FACE experiments data.