Ten secondary metabolites in phloem of different strains of poplars were extracted by different chemical methods and their contents were determined.The effect of different treatment process for samples on the extraction efficiency of tannin,phenols and phenolic acids was studied in detail.The results showed that the contents of phenol and pyrocatechol in Populus alba×P.berolinensis were maximum,while these values were minimum in P.nigra.The temperature of sample preparation had influence on the extraction e...