Some photosynthetic parameters of 6.0 mM phosphoric acid treated plants and control were measured using the CIRAS-2 Portable Photosynthesis System. The result showed that Pn and WUE of plants treated with phosphoric acid increased significantly compared with those of the control plants, while there was no significant difference in Gs and Ci between the treated plants and control (Table 4). Pn and WUE increased 28.8% and 16.1%, respectively.