Abstract:

Initiation and development of resin ducts were studied in cortex of stem of Pinus massoniana Lamb. by thin section. It is shown that the development of resin ducts can be divided into four stages: the initial stage, the intercellular space forming stage, the lumen expanding stage and the mature stage. To further investigate the original mode of resin ducts, cytochemical localization of pectinase with a transmission electron microscope (TEM) was conducted. Results showed that the pectinase was active during resin duct development. At the initial stage, reaction products of pectinase first appeared in the corner of swollen cell wall among the future epithelial cells and later along the walls. At the intercellular space forming stage, reaction products occurred in the cell wall/intercellular space interface and its density decreased while the intercellular space enlarged. At the mature stage, no reaction products were found in the walls of the epithelial cells. These results indicate that pectinase catalyzes the degradation of the middle lamella of the epithelial cells during the resin ducts development. The cytochemical evidence supports that the resin ducts are formed by schizogeny. This report represents the first direct evidence for the involvement of pectinase in resin ducts formation .

Key words: initiation and development, cytochemical localization, pectinase, resin ducts, Pinus massoniana