Cloning and Expression Analysis of Drought-tolerance Related Gene Gp-LEA in Grimmia pilifera Construction of cDNA Library in Grimmia pilifera Under Drought Stress Cloning and Expression Analysis of GpSOD in Grimmia pilifera Cloning and Expression Analysis of GpUCH Gene in Grimmia pilifera Extraction of totle RNA from dry Grimmia pilifera The Method Study of Extracting Total RNA from Grimmia pilifera P.Beauv Photochemical analysis of PSII in response to dehydration and rehydration in moss Grimmia pilifer P.Beauv