Effects of Ozone on Photosynthesis of Several Plants

In order to investigate the effect of ozone on photosynthesis of Machilus pauhoi, Lindera setchuenensis, Phoebe bournei, Phoebe chekiangensis and Machilus thunbergii, the study was carried out in 12 open-top chambers( OTCs) with different levels of ozone in Qianyanzhou experimental station, and net photosynthesis rate (Pn) and stomatal conductance (Cond) were detected. The results indicated that ozone treatments changed the variation trend of photosynthesis of all tested plants, but ozone exposure did not always play an inhibitory role on them. In fact, photosynthesis changed with ozone concentration, experimental period, season and specific species. Exposed to ozone could even promote Pn to a peak in a short term, and the indicator of plants treated with ozone was higher than that of the control at this point. Low and medium concentrations of ozone treatment enhanced Pn of Phoebe bournei and Machilus thunbergii. The peak of treatment group also came earlier because of ozone. Furthermore, the positive correlation between Pn and Cond did not existed under the condition of ozone. Machilus thunbergii had the strongest resistance to ozone, followed by Phoebe bournei, by comparison, Phoebe chekiangensis, Machilus pauhoi and Lindera setchuenensis were more sensitive.