二氧化氮对樟树幼苗生长及光合作用的影响

采用开顶式人工熏气装置，对1年生樟树幼苗进行了为期2个月不同体积分数NO₂(0.1、0.5和4.0 μl·L^-1)熏气试验，研究其对幼苗生长及光合作用的影响.结果表明:0.5和0.1 μl·L^-1 NO₂处理促进了樟树幼苗生长，而4.0 μl·L^-1 NO₂处理则抑制其生长.各处理樟树幼苗叶片净光合速率(P_n)日变化呈不对称的双峰型曲线，存在光合“午休”现象;在光合日进程中，0.5 μl·L^-1 NO₂处理使叶片P_n提高，最大值达8.542 μmol CO₂·m^-2s^-1，4.0 μl·L^-1NO₂处理的大多数时段使P_n降低，而0.1 μl·L^-1 NO₂处理对P_n的影响则依时段而不同;0.5和4.0 μl·L^-1 NO₂处理提高了叶片气孔导度(G_s)和胞间CO₂浓度(C_i)的最大值和最小值，0.1 μl·L^-1 NO₂处理提高了C_i的最大值和最小值，降低了G_s的最大值和最小值.熏气处理中、后期，0.5μl·L^-1 NO₂处理叶片的日均净光合速率显著高于其他处理.在熏气处理前期，0.5和4.0 μl·L^-1 NO₂处理使叶片最大PSⅡ的光能转换效率(F_v/F_m)显著下降;在熏气处理后期，4.0 μl·L^-1 NO₂处理的叶片F_v/F_m仍显著低于对照.

Effects of NO2 on Cinnamomum camphora seedlings growth and photosynthesis

A 2-month fumigation experiment was conducted with opened top chambers to study the effects of different concentration (0.1, 0.5, and 4.0 μl·L-1) NO2 on the growth and photosynthesis of 1-year Cinnamomum camphora seedlings. Fumigation with 0.1 and 0.5 μl NO2·L-1 promoted the growth of the seedlings, while with 4.0 μl NO2·L-1 was in adverse. The diurnal variation of net photosynthetic rate (Pn) presented two-peaks, with an obvious depression in midday. 0.5 μl NO2·L-1 increased the Pn, the maximum of Pn reached 8.542 μmol CO2·m-2s-1; 4.0 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 0.5 and 4.0 μl NO2·L-1 increased the maximal and minimal values of stomatal conductance (Gs) and intercellular CO2 concentration (Ci), while 0.1 μl NO2·L-1 increased the maximal and minimal values of Ci but decreased the maximal and minimal values of Gs. At the middle and late stages of fumigation, the mean Pn of the seedlings treated with 0.5 μl NO2·L-1 was significantly higher than that treated with 0.1 and 4 μl NO2·L-1. At the early stage of fumigation, 0.5 and 4.0 μl NO2·L-1 significantly decreased the maximal PSⅡ efficiency (Fv/Fm); and at the late stage, 4.0 μl NO2·L-1 still decreased the Fv/Fm significantly.