Studies On Change Of Urushiol Content In Raw Lacquer And The Structure Of Bark Of Toxicodendron Vernicifluum (Stokes) F.A. Barkley In Different Seasons

Toxicodendron vernicifluum (Stokes) F. A. Barkley, which originated in China and distributed in most province or region of China, is an important kind of economical tree of Anacardiaceae Toxicodendron. The main product of Toxicodendronvernicifluum (Stokes) F. A. Barkley——raw lacquer, which has a reputable name of"king of paint", is a kind of excellent natural paint and it is also the important material of modern industry, agriculture, national defense, science and technology and civil. The people of our country have been planting lacquer tree and using raw lacquer for almost 7000 years. The leaves, flowers, roots, skin, fruits, dry lacquer and heartwood of lacquer tree can all be used as medicine. The flowers of lacquer tree contain abundant sweet liquid and lacquer trees are important nectar source plant. Lacquer oil, which is processed by lacquer seeds, can be edible and used as material of paint. We studied the distribution and structural characters of laticiferous canals, the structure that secreting and reserving raw lacquer, by plant anatomical means, and compared the similarities and differences of the structure of laticiferous canals in every organs, in the same, we put the emphasis on studying the structure of bark of lacquer tree, analyzed and generalized the change of the structure of bark in different seasons. We also studied the change of urushiol content in raw lacquer in different seasons and in the lacquer tapping season by spectrophotometry. The main results acquired through these systematic studies as follows:1. The structure that secreting raw lacquer are laticiferous canals, which distribute mainly in phloem of every organ of lacquer tree. Except seeds, the roots, stem, leaves, flowers and fruits all have laticiferous canals, the laticiferous canals mainly distribute in phloem of vascular bundle in every organ and minority laticiferous canals distribute in the pith of stem. The laticiferous canal is secretory canal, consists of a canal which rounded by one layer of epithelial cells and the multiple layers of sheath cells around them. The diameter and the layers of sheath cells of laticiferous canals are different in different organs of lacquer tree. The diameter of laticiferous canals in stem and fruits are large, they are large-scale laticiferous canal. The diameter of laticiferous canals in other organs are small, the diameter of laticiferous canals in calyx and stamen are most small. The pericarp is developed by ovary wall, but the structure of laticiferous canals in fruits is very different from the structure of laticiferous canals in ovary wall.2. The bark of lacquer tree which is the main part of lacquer tapping is made up of secondary phloem in the stem of lacquer tree and periderm and the dead bark around it. Secondary phloem consists of the vertical system and the radial system, the vertical system consists of sieve vessels, companion cells, parenchyma cells, stone cells and laticiferous canals; the radial system is ray. According to the shape and function of sieve vessels, the secondary phloem can be divided into functional phloem and non-functional phloem. Except the number of laticiferous canals in a unit, the diameter of laticiferous canal, the proportion of functional phloem and non-functional phloem and the size, number and alignment of cells in tissues rounding the laticiferous canals, the structure of bark of the same kind of lacquer trees in different months is nearly the same. In our study, we measure and statistic some indexes of choosing lacquer tree in different months and analyze the change patterns.3. Through determining the change of urushiol content in raw lacquer in March to November and in lacquer tapping season, it is proved that the experience of people tap the raw lacquer in July and August is scientific and reasonable. In lacquer tapping season, the urushiol content in late July and early August is high and showing the increasing trend. So we concluded that the period from late July to early August is the best period for lacquer tapping, the raw lacquer flow of this period is large, it is easy to tap lacquer, the urushiol content of this period is high, especially in early August, the urushiol content is highest. Based on these, we study on the relativities between the structure of bark and the change of urushiol content in raw lacquer, which provide scientific thinking for determining lacquer tapping best period and improving the productive and quantity..