Does CO2 ameliorate phytotoxic effects of O3?, Prof. Ibrahim Hassan

Potato (Solanum tuberosum L. cv. Kara) was grown in Open-Top Chambers (OTCs) in Northern Egypt at ambient (ca 350 ppm) or doubled CO2 (ca 690 ppm) either in charcoal-filtered air (15 nl l−1) or in non-filtered ambient air (78 nll−1 O3) to investigate the changes in physiology and yield under long-term elevated CO2and/or O3 throughout 100 days. Ambient O3 level reduced net photosynthetic rates, number and weight of tubers by 18%, 41% and 21%, respectively, whereas elevated CO2 caused the opposite effect where it increased the same parameters by44%, 37% and 20%, respectively. Significant O3 x CO2 interactions were detected. However, O3 caused an increase in GR and POD by 18% and 35%, respectively, while CO2 caused an increase in POD only by 46%, and there was no effect of O3 and/or CO2 on other enzymes. The results of this study are discussed in relationto predicted atmospheric changes.