Abstract:

Lacquer (Toxicodendron vernicifluum) is a unique economic tree species in China, raw lacquer (also known as oriental lacquer) is the sap from phloem of lacquer trees. In this study, the phloem structure and seasonal development of 3 different lacquer varieties were investigated using the anatomical technique. The results showed that phloem structure was basically similar in the 3 varieties. The secondary phloem consisted of sieve tubes, companion cells, parenchyma cells, stone cells and secretory ducts in longitudinal orientation, and phloem rays in radial alignment. In the newly formed secondary phloem, sieve tube had been developed to mature with transporting function, parenchyma and phloem rays were still tender, and the secretion ducts were in the differentiating period. This part of phloem had transportation function. Outside of this part, it was the secondary phloem formed in previous years, and its sieve tubes became atrophic and lost transporting function, and this part of phloem was known as the non-functional phloem and occupied most of the area of phloem. In non-functional phloem, the size of parenchyma cells gradually increased and squeezed sieve tubes; secretory ducts developed to mature and secreted a large number of lacquer in the canals, the phloem rays increased to 3-5 layers. Moreover, some of the parenchyma cells differentiated into stone cells clustered in non-functional phloem. The structure and development characteristics of lacquer tree phloem were related to their physiological functions. This study would provide a scientific basis for tapping lacquer reasonably.

Key words: Toxicodendron vernicifluum, phloem, laticiferous canals, structure, development