Characteristics of photosynthetic diurnal variation at the reproductive stage of Eupatorium adenophorum

The CI340 photosynthetic system was used to monitor the photosynthetic diurnal variation of Eupatorium adenophorum at the reproductive stage and determine the relationship between photosynthetic diurnal variation and environmental factors for providing the useful information for control E. adenophorum in natural condition. The results of this study indicated that the diurnal variation of net photosynthetic rate (Pn) presented a doublepeak curve, peaking at 11:00 and 13:00, and this study also showed an obvious midday depression. The stomatal conductance (Gs) and transpiration rate (Tr) were positively consistent with Pn from 9:00 to 14:00, and then increased slightly, and they showed a threepeak curve. The intercellular CO2 concentration (Ci) was significantly negative correlation with stomatal limitation value (Ls) (R=-0.997 6**), presenting the singlepeak curve. At the reproductive stage of E. adenophorum, Pn was mainly affected by Tr, Leaf Water Deficit and leaf temperature, and greatly regulated by photosynthetic active radiation (R=0.860 0**）. This study suggested that the comprehensive control measures of E. adenophorum focused on choosing the more strongly photosynthesis replaced plants, herbicide, chemical control time.