A Diagnostic Experiment and Study of the Influence of O₃ on Pakchoi

A long time experiment on pakchoi in five O₃ concentration treatments is made by using the OTC-1 open top chamber. The results show that lower O₃ concentrations (25×10 ^–9 ~ 40×10 ^–9 and 50×10 ^–9) have chronic injury to pakchoi. When O₃ concentration is up to 100×10 ^–9 or 200×10 ^–9, green pakchoi leaves faded and lost water. Increasing O₃ content in ambient air may lead to shorter plant height and smaller plant pattern as well as the decreased leaf number, leaf area, photosynthesis rate, biological yield and economy yield. In addition, the experiment shows that pakchoi mesophyll and epidermis was influenced first when pakchoi in normal growing condition moved into the chamber with the O₃ concentration being 100×10 ^–9 or 200×10 ^–9, but the veins of new leaves in the clamber twised and changed form first .