Abstract: The photosynthetic characteristics of Phalaris arundinacea Linn.were studied by using portable LI-6400 photosynthesis instrument.The diurnal changes of net photosynthetic rate(P_n) and its major influencing factors,including photosynthetically active radiation(PAR),stomatal conductance(Cond),intercellar CO₂ concentration(C_i),leaves temperature (T_l),air temperature(T_a),and transpiration rate(T_r),were measured at different growing stages to analyze photosynthesis diurnal dynamics. The results show that the diurnal processes of photosynthetic rates exhibited a double peak curve at different growing stages with an obvious phenomenon of midday depression of photosynthesis.But the main and second peak of last ten-day of May appeared about one hour behind those of first ten-day of April,and the former P_n was higher than that of the later.The reasons for midday depression of photosynthesis were different at different growing stages,with stomatal limitation in early April and non-stomatal limitation in late May,respectively.The correlation coefficients among photosynthesis factors were different,even opposite at different growing stages.The seasonal dynamics of photosynthesis rate of P.arundinacea showed single-peak curve with the peak in middle and late April.According to the light intensity and CO₂ concentration response curve of photosynthetic rate,the light compensation point was at 45.6μmol·m^-2·s1,light saturation point at 1825 μmol·m^-2·s^-1,apparent quantum yield at 0.047 mol·mol^-1,dark respiration rate at 2.1429 μmol·m²·s^-1,CO₂ compensation point at 76 μmol·mol^-1,saturation point at 923 μmol·mol^-1,and carboxylation rate at 0.0556.The data indicate that P.arundinacea is a kind of C₃ sun plant with high photosynthetic efficiency.

Key words: Phalaris arundinacea Linn., Net photosynthetic rate, Light intensity response curve, CO₂ concentration response curve

摘要： 对虉草(Phalaris arandinacea)光合特性的研究表明:不同生长阶段虉草净光合速率日变化均呈双峰曲线,光合"午休"现象明显,但5月下旬主、次峰均滞后于4月初1 h,净光合速率后期大于前期,导致光合"午休"的原因不同,4月初为气孔限制因素,而5月下旬为非气孔限制因素。不同时期各生理生态因子间的相关系数不同。虉草净光合速率季节动态呈单峰曲线,4月中下旬最高。虉草的光补偿点为45.6μmol·m^-2·s^-1,光饱和点为1825μmol·m^-2·s^-1,表观光量子效率为0.047 mol·mol^-1,暗呼吸速率为2.1429μmol·m^-2·s^-1;CO₂补偿点为76μmol·mol^-1,饱和点为923μmol·mol^-1,羧化效率为0.0556。数据显示,虉草是一种高光效C₃阳性植物,对草地生态系统的稳定意义重大。

关键词: 虉草, 净光合速率, 光合响应曲线, CO₂响应曲线