Abstract:A 2-month fumigation experiment was conducted with opened top chambers to study the effects of different concentration (01, 05, and 40 μl·L-1) NO2 on the growth and photosynthesis of 1-year Cinnamomum camphora seedlings. Fumigation with 01 and 05 μl NO2·L-1 promoted the growth of the se edlings, while with 40 μl NO2·L-1 was in adverse. The diurnal variat ion of net photosynthetic rate (Pn) presented two-peaks, with an obvious depression in midday. 05 μl NO2·L-1 increased the Pn, the maxi mum of Pn reached 8542 μmol CO2·m-2s-1; 40 μl NO2·L-1 decreased the Pn in most period of time; while the effect of 0 .1 μl NO2·L-1 varied with time period. Fumigation with 05 and 4.0 μ l NO2·L-1 increased the maximal and minimal values of stomatal conducta nce (Gs) and intercellular CO2 concentration (Ci), while 0.1 μl N O 2·L-1 increased th e maximal and mi nimal values of Ci but decreased the maximal and minimal values of G s. At the middle and late stages of fumigation, the mean Pn of the seedlings treated with 05 μl NO2·L-1 was significantly higher than that treated with 01 and 4 μl NO2·L-1. At the early stage of fumigation, 05 and 40 μl NO2·L-1 significantly decreased the maximal PSⅡ efficiency (Fv/Fm); and at the late st age, 40 μl NO2·L-1 still decreased the Fv/Fm significantly.