Abstract
Potato ( Solanum tuberosum L.cv. Kara) was grown in Open-Top Chambers (OTCs) in Northern Egypt at ambient (ca 350 ppm) or doubled CO (2) (ca 690 ppm) either in charcoal-filtered air (15 nll(- 1)) or in non- filtered ambient air (78 nll(- 1) O-3) to investigate the changes in physiology and yield under long-term elevated CO (2) and/or O-3 throughout 100 days. Ambient O (3) 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 by 44%, 37% and 20%, respectively. Significant O (3) x CO (2) interactions were detected. However, O (3) caused an increase in GR and POD by 18% and 35%, respectively, while CO (2) caused an increase in POD only by 46%, and there was no effect of O (3) and/or CO (2) on other enzymes. The results of this study are discussed in relation to predicted atmospheric changes.