Abstract: Phylanthus emblica is the characteristic and dominant species of the vegetation in xerothermic valley. With the simulation of the climate conditions in April in Yuanmou basin, a typical area in the xerothermic valley of Jinsha River, this paper studied the vigor dissipation of P. emblica seeds, and related physiological and biochemical mechanisms. The natural regeneration of P. emblica population was also investigated. The results showed that with prolonging high temperature and drought, the seed vigor of P. emblica decreased, the relative electrical conductivity, Pro content, and MDA content in seed had an increasing trend, and the respiration intensity, activities of SOD, POD and CAT, and soluble sugar content in seed showed a single-peaked pattern. The decrease of membrane protective enzyme activities and of protective matter content was the key factor for the decrease of seed vigor. The period from the 18th to the 24th day of stress treatment was the critical period for the stress-resistance of P. emblica seeds. In order to improve the natural regeneration ability of P. emblica seeds, some artificial measures should be taken from the last ten-day of April to the early and mid March of the year.

Key words: Spring wheat, Crop evapo-transpiration, Reference evapo transpiration, Crop coefficient