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用LI-6400型便携式光合测定仪观测7种生长年限苜蓿的光合作用日变化特征。结果表明:①7种生长年限苜蓿的净光合速率Pn、蒸腾速率Tr、水分利用效率WUE及气孔导度(Gs)日变化均呈现“双峰”曲线,有明显的光合“午休”现象,但不同年限Pn、Tr、WUE和Gs的高峰和低谷出现的时刻不同;②根据Pn、胞间CO2浓度Ci、气孔限制值Ls的变化方向,推测4年、6年苜蓿光合速率的下降同时受气孔和非气孔因素限制,而8年、12年、14年、18年、26年苜蓿光合速率的下降主要受非气孔因素限制;③从苜蓿的净光合速率看,日均净光合速率最高的是6年生苜蓿,苜蓿的最佳利用期为6年。
The diurnal variation of photosynthesis of alfalfa in seven growth years was observed by LI-6400 portable photosynthesis system. The results showed that: ① The net photosynthetic rate (Pn), transpiration rate (Tr), water use efficiency (WUE) and stomatal conductance (Gs) of alfalfa in seven growth years all showed “double peak” However, the peak times and troughs of Pn, Tr, WUE and Gs were different in different years; ② According to the change direction of Pn, intercellular CO2 concentration Ci and stomatal limitation value Ls, the photosynthetic rate of alfalfa decreased at 4 years and 6 years The photosynthetic rate of alfalfa decreased at 8, 12, 14, 18 and 26 years. The decrease of photosynthetic rate was mainly attributed to non-stomatal factors. From the net photosynthetic rate of alfalfa, the average net photosynthetic rate The highest is 6-year-old alfalfa, the best use of alfalfa is 6 years.