Abstract:Photosynthetic characteristics of Juglans hopeiensis Hu ‘Yihe 1’were studied by an open gas analysis system of model CI-301PS in the orchard. The results indicated that the light compensation and light saturation points of Juglans hopeiensis Hu were 50 μmol·m- 2 ·s- 1 and 1643 μmol·m- 2 ·s- 1 , respectively. The optimum temperature of Pn was 29 ℃. The curve of diurnal variation of Pn in Juglans hopeiensis Hu showed two peaks with a minimum at noon. Two peaks appeared in the curve of seasonal variation of Pn of Juglans hopeiensis Hu, the first peak occurring in May, and the second peak occurring in August. The diurnal change of Pn in Juglans hopeiensis Hu was influenced by stomatal conductance, PAR (photosynthetic available radiation) , leaf temperature, intercellular CO2 concentration and transpiration rate. The Pn of Juglans hopeiensis Hu were lower than that of English-walnut, and approached that of Manchurian walnut.