Abstract: Based on the estimation of transpiration rate by energy balance theory, and combining the estimations of atmospheric water potential and leaf and atmosphere resistance, a leaf water potential model retrieved from remote sensing was built. Some physiological and meteorological parameters observed by CI-301 apparatus were used for testing the retrieval precision of leaf water potential; and the sensitivity of the responses of leaf water potential to physiological and climate drought in arid and semiarid region was analyzed. The results showed that leaf water potential was a good index for reflecting drought, by which, thecharacteristics of physiological and climate drought could be well expressed. The retrieval error of leaf water potential from remote sensing was between 3.2% and 17.3%, indicating that the leaf water potential estimated by remote sensing could be used for monitoring drought and evaluating water stress. In the dry year of 2005 in Gansu, the leaf water potential was between -2 and -3 MPa in May and about -2 MPa in June, and the drought degree was correlated to crop species.

Key words: Phytoplankton, Ribulose-1, 5-bisphosphate carboxynase/oxygenase large subunit gene(rbcL), Molecular genetic diversity