Analysis Of Secondary Tissue Structure And Bark Extractives Of Lagerstroemia Indica And Lagerstroemia Limii

Lagerstroemia indica L.and Lagerstroemia limii Merr.both belong to Lagerstroemia in the family Lythraceae.Lagerstroemia indica is widely distributed in eastern and southern Asia,and Lagerstroemia limii is an endemic specie to China.The roots,stems and leaves of Lagerstroemia species have medicinal value,and Lagerstroemia indica bark has a long history of being used as Chinese traditional medicine.However,there is no report on the secondary tissue anatomical structure and bark extractives composition of Lagerstroemia indica and Lagerstroemia limii.The aim of this thesis is to enrich the structural characteristics of Lagerstroemia indica and Lagerstroemia limii.The ticklish phenomenon of Lagerstroemia indica is explained from the anatomical structure of wood in this thesis.The seasonal variation of secondary tissues,callose and phloem crystals are also observed.and explore the compound composition of bark extractives from Lagerstroemia indica and Lagerstroemia limii.The secondary tissue structure,seasonal variation,callose and phloem crystals between Lagerstroemia indica and Lagerstroemia limii were observed.Results are compared by means of microsection,tissue maceration,optical microscope,fluorescence microscope,polarizing microscope and scanning electron microscope.Bark samples were extracted with three solvents,such as benzenol,n-hexane and ethyl acetate.The extractives were analyzed by gas chromatography and mass spectrometry.The main conclusion are as follows.(1)The wood anatomical differences between Lagerstroemia indica and Lagerstroemia limii were in the distribution and number of vessels,types of wood fibers and types of vestured pits:Lagerstroemia indica was a wood diffuse-porous,vessels 63/mm~2,with septate fibers and the type of vestured pits was spheroid.Lagerstroemia limii was a semi-ring-porous wood,vessels 35/mm~2,with non-septate fibers and the type of vestured was dendritic.Other anatomical structure differences were not obvious:vessels were round and oval,simple perforation plates,axial parenchyma vasicentric and axial parenchyma bands more than three cells wide,all rays were exclusively uniseriate and non-storied.Measurement data showed that in the average tangential diameter of vessel,average length of vessel and average length of fiber,Lagerstroemia indica were 55μm,307μm,572μm;Lagerstroemia limii were 72μm,321μm,635μm.The boundary between conducting phloem and nonconducting phloem was not distinct of Lagerstroemia indica and Lagerstroemia limii,and the sieve tubes were rectangular with companion cells beside some sieve tubes.The area and length of the sieve tubes of Lagerstroemia indica were 133μm~2 and 236μm,and those of Lagerstroemia limii were 186μm~2 and 242μm.The most remarkable difference of phloem was that Lagerstroemia indica did not have phloem fiber cells and Lagerstroemia limii had phloem fiber cells.It was speculated that the"itch"fear of Lagerstroemia indica trees was related to the lack of phloem fibers.According to the anatomical structure of xylem and phloem of Lagerstroemia indica and Lagerstroemia limii,the IAWA codes were written respectively.(2)The cambium of Lagerstroemia indica and Lagerstroemia limii both began to meristem in May.In the process of development from dormant period to active period,the cambium cells of Lagerstroemia indica increase from two to four layers and become irregular in shape.The secondary xylem cells differentiated in May and the phloem cells differentiated in June were not significantly different from the earlier cells.The newly formed phloem cells expanded in September and cell walls thickened in October.During the active period,the number of cambium cells of Lagerstroemia limii increased from 2 layers to 6 layers,and the shape of the cells was deformed obviously.After entering the dormant period,the cambium cells returned to the regular arrangement of 2 layers.The cambium of Lagerstroemia limii differentiated inwards to form xylem cells in May and June,and outwardly to form phloem cells in July.The newly differentiated phloem cells grew in area in August,and their cell walls thickened in September.The thickening of the secondary wall of the phloem fiber cells of Lagerstroemia limii showed an obvious change pattern.From June to December,the shape of the fiber cells was rounded and polygonal,and the distribution types were banded,scattered and clustered.The number of fiber cells with secondary wall thickening showed the trend of increasing-decreasing-increasing.(3)The callose of phloem of Lagerstroemia indica and Lagerstroemia limii were both decreased in active period and gradually increased during dormant period.Callose of Lagerstroemia indica was not abundant and distributed in a wide range.Callose only existed in conducting phloem.Callose was disappeared during active period and gradually increased during the dormant period.Callose of Lagerstroemia limii was more abundant than that of Lagerstroemia indica.Callose is distributed in conducting phloem and nonconducting phloem.In conducting phloem,callose in sieve tube was less in active period and more in dormant period.In nonconducting phloem,callose deposition occurs synchronously with the thickening of the secondary wall of the phloem fibers.The number of phloem crystals of Lagerstroemia indica and Lagerstroemia limii decreased during the active period and gradually increased during the transition from the active period to the dormant period.Since calcium plays an important role in promoting and preserving flowers,it is speculated that the low number of phloem crystals in Lagerstroemia indica and Lagerstroemia limii during the active stage was due to the breakdown of calcium oxalate crystals in the phloem to provide calcium for flowering.At the end of the active period,the excess calcium again combines with oxalic acid to form calcium oxalate crystals in phloem.(4)The bark of Lagerstroemia indica was extracted by benzenol,n-hexane and ethyl acetate,the contents of extractives were respectively 4.45%,1.95%and 2.15%,and the type of compounds identified by GC-MS were 24,21 and 21.The bark of Lagerstroemia limii was also extracted by benzenol,n-hexane and ethyl acetate,the contents of extractives were respectively 5.05%,2.10%and 1.40%,and the type of compounds identified by GC-MS were27,19 and 19.Among the three extraction solvents benzenol,n-hexane and ethyl acetate,benzenol was the best extraction solvent.The extractives content of benzenol was the highest both in the bark samples of Lagerstroemia indica and Lagerstroemia limii,and the number of benzenol extractives were the largest.There were medicinal compounds in the bark of Lagerstroemia indica and Lagerstroemia limii extracted with benzenol,n-hexane and ethyl acetate.Some compounds with medicinal value were found in the extractives,such as palmitic acid,linoleic acid,stearic acid,squalene,phytol,palmitamide and oleic acid.The functions of medicinal compounds mainly focus on anti-inflammatory,antioxidant,prevention of cardiovascular disease,anti-tumor and so on.The bark of Lagerstroemia indica and Lagerstroemia limii may both have certain medicinal value.The bark resources of Lagerstroemia indica and Lagerstroemia limii are of great research significance and potential application value.