Photosynthetic diurnal change of white clover and orchardgrass intercroping in apple orchard

The photosynthetic diurnal change characteristics of orchard grass (Dactylis glomerata cv. Amba) and white clover (Trifolium epens cv. Haifa) intercroping in the apple orchard were studied using LI6400 portable photosynthesis system．The results indicated that the net photosynthesis rate (Pn)，transpiration rate (Tr), stomata conductance (Gs) and water use efficiency (WUE) of Haifa and Amba showed a singleapex curve, the respective apex occurred at 11:00 or 13:00. The intercellular CO2 concentration (Ci) of Haifa and Amba showed the U shape with the lowest values occurred respectively at 11:00 and 13:00. The leaf daily average WUE of Amba showed no significant difference (P0.05) compared with that of Haifa, but the leaf daily average LUE showed significant difference (P0.01). The comprehensive results certificated furtherly Amba has stronger shade tolerance and greater photosynthetic capacity than that of Haifa.