黄土高原地区不同生长年限苜蓿光合作用的日变化规律研究

Study on Daily Dynamics of Photosynthesis of Alfalfas with Different Growing Years in the Loess Plateau

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。

Daily dynamics of photosynthetic characteristics of alfalfas with different growing years in the Loess Plateau were monitored using Portable LI -6400 Photosynthesis System. The results were summarized as follows ： The curves of diurnal variation in Pn, Tr, 1VUE and Gs of 7 alfalfa leaves had two peaks, and there were differences in the time and the value of the peaks occurred in terms of Pn, Tr, WUE and Gs. Based on the changing tendencies of Pn, Ci and Ls, it was speculated that the midday depression in 4 and 6 years alfalfa were controlled by stomatal factor and non. stomatal factor, while 8, 12, 14, 18 and 26 years alfalfa were controlled by stomatal factor. Concerning Pn, the 6 years alfalfa has the highest Pn, so the best use period is 6 years.