Fruit of pear cultivars Xizilu,Jushui,and 'Dangshansu' were used as materials for studying the relationship between sclereids (grit cells) and related enzymes. The results showed that the density of sclerid group was high at the early stage, then descended with the fruit developing, and one month before maturity it retained stable; the diameter of sclerid group increased gradually. As a whole, activities of all the three enzymes declined gradually in the course of fruit development; and PAL (phenylalanine a...