Diurnal dynamics of photosynthesis under three rotation systems (potato-wheat-A. sinensis, A. sinensis-wheat-A. sinensis,and wheat-A. sinensis-A. sinensis rotation system over a three-year period) were monitored by using portable CI-310 Photosynthetic Gadget. Based on the results, diumal variations in A. sinensis Pn, Tr, Gs and Ci exhibited di-peak curves, with obvious midday (12:00) depressions. However, difference existed in the time and value of diurnal variation curve peaks and troughs for Pn, Tr, Gs and Ci. The diurnal tendencies of Pn, Ci and Gs suggested that the midday depression was caused by stomatal conditions. Wheat-A.sinensis-A. sinensis and A. sinensis-wheat-A. sinensis rotation systems significantly decreased leaf chlorophyll content in A. sinensis.Diurnal average values of Pn, Tr, Gs and Ci under potato-wheat-A, sinensis rotation system were significantly higher than those under wheat-A. sinensis-A. sinensis rotation system. Continuous cropping significantly decreased A. sinensis leaf chlorophyll content and Gs, Ci, Pn and Tr, which resulted in decreased Ao sinensis yield.%利用CI-310 便携式光合作用系统,测定正茬(连作0年)、迎茬(隔年连作)、重茬(连作2年)3种种植方式下当归叶片的光合参数,研究其日变化特征.结果表明:3种种植方式下当归叶片净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)和胞间CO2浓度(Ci)的日变化均呈"双峰"曲线,12:00 时存在明显"午休"现象,但不同茬口Pn、Tr、Gs和Ci高峰和低谷出现的时刻和值不同;根据Pn、Ci和Gs的变化方向,推测当归叶片的光合"午休"受气孔因素影响;重茬和迎茬极显著(P<0.01)降低当归叶片叶绿素含量;正茬种植方式下当归叶片Pn、Gs、Ci和Tr的日均值均极显著(P展开▼
