关键词: 虉草, 净光合速率, 光合响应曲线, CO₂响应曲线

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