Abstract:Fruits of pummelo [Citrus grandis (L.) Osbeck ‘Guanxi-miyou’] from old-age trees occurred easily juicy sac granulation and proper-age trees not occurred juicy sac granulation were used to study the relationship between juicy sac granulation and cell wall metabolism during the fruit mature stage. The index of juicy sac granulation of fruits from the old-age trees increased with fruit maturing. Pectinesterase (PE), polygalacturonase (PG) and cellulase in juicy sacs kept low activities, and the contents of protopectin, cellulose and semicellulose were high during the development of juicy sac granulation. At the early and the rapid developmental stages of juicy sac granulation, the contents of cellulose and semicellulose were enhanced significantly. In contrast, the index of juicy sac granulation of fruits from the proper-age trees had little change with the fruit maturing. The activities of PE, PG and cellulase in juicy sacs were high and the contents of protopectin, cellulose and semicellulose were low. It suggested that the activities of PE, PG and cellulase, and the contents of protopectin, cellulose and semicellulose were closely related to juicy sac granulation of pummelo fruits.