Effects of ambient and elevated CO2 and ozone on physiological characteristics, antioxidative defense system and metabolites of potato in relation to ozone flux

The present study was performed to evaluate the effects of different levels of carbon dioxide (ambient (382 ppm) and elevated (570 ppm)) and O-3 (ambient (50 ppb) and elevated (70 ppb)) on physiological and biochemical characteristics of potato (Solanum tuberosum L cv. Kufri chandramukhi) using open top chambers. Ozone flux in leaves at 60 days after emergence (DAE) showed a trend in decreasing order as ACO(2) + EO3 > ACO(2) + AO(3) > ECO2 + EO3 > ECO2 + AO(3) > ACO(2). Ozone flux was found to correlate directly with the plant's photosynthetic performance and antioxidative response under different combinations of ambient and elevated CO2 and O-3. Maximum O-3 flux under ambient CO2 and elevated O-3 (ACO(2) + EO3) caused the highest increase in lipid peroxidation and solute leakage and reductions in chlorophyll content along with photosynthesis rate. Elevated O-3 stimulated the activities of superoxide dismutase (SOD), glutathione reductase (GR) and ascorbate peroxidase (APX) under ambient (ACO(2) + EO3) and elevated CO2 (ECO2 + EO3). However, all these alterations were alleviated by elevated CO2, indicating that oxidative stress on cell membrane was minimized and depression in photosynthesis rate recovered under combination of ECO2 + EO3. Elevated CO2 increased antioxidative enzymes and total phenolics in the leaves under ECO2 + EO3 at 30 DAE, contributing to the protection against O-3 induced oxidative stress. However, at 60 DAE, the protection provided by ECO2 was mainly by reducing the ozone flux inside the leaves under ECO2 + EO3. The study suggests that future increase in atmospheric concentrations of CO2 will ameliorate O-3 damage to potato due to reduced O-3 uptake, increased carbon assimilation and by enhancing antioxidative property of leaves as an additional factor. (C) 2014 Elsevier B.V. All rights reserved.