Growth and fruiting of tomato as influenced by elevated carbon dioxide and ozone

'Tiny Tim' tomato plants were exposed to five CO₂ treatments (375 (ambient), 450, 525, 600 or 675 μmol mol^-1 ) in combination with 0₃ (0 or 80 nmol mol^-1 . Biomass was evaluated following 3,5,7 and 13 wk exposure. Biomass following 13 wk exposure also included weekly harvests of mature tomato fruit beginning week 8. Carbon dioxide enrichment significantly enhanced total vegetative plant d. wt at each harvest, as well as cumulative yield of mature fruit, whereas O₃ significantly suppressed total vegetative plant d. wt at each harvest and reduced total cumulative fruit yield. The magnitude of these changes varied with the development of tomato from early growth to mature fruit yield. Carbon dioxide enrichment reduced the detrimental effects of O₃ on total vegetative plant d. wt of tomato following 3, 5, 7 and 13 wk exposure. Final mature fruit yield was 24% higher under enriched GO₂ treatments than in ambient CO₂ . Ozone suppressed final yield by 31%, following exposure to 80 nmol mol^-1 O₂ , when compared with exposure to charcoal-filtered (CF) air. The impacts of both CO₂ and O₃ on yield were, however, dependent upon the presence or absence of the other gas. In the absence of O₃ , yields were very similar for the ambient and elevated CO₂ treatments, but in the presence of O₃ , yields under ambient CO₂ were greatly suppressed whereas yields under elevated CO₃ were similar to those in the absence of O₃ . Thus, enriched CO₂ ameliorated most of the suppressive effect of O₃ on yield of mature fruit.