| Cerasus yedoensis belongs to sub-family Prunoideae of Rosaceae.The bark of C.yedoensis has excellent tensile property in tangential direction and contains phellem.However,there are few studies on the anatomical structure of bark from C.yedoensis and observation on its meristematic process.In this research,the young branches of C.yedoensis in Nanjing Forestry University were sampled during different seasons,sectioned and observed to analyze the seasonal regularity during phellem formation.Different dyes combined with fluorescence microscope observation were used to characterize the cell wall of phellem from C.yedoensis.After depolymerization with sodium methoxide and methanol solution,the suberin was extracted from the bark of C.yedoensis.The composition of the monomer was determined by mass spectrometry,and the fluorescence characteristics of the monomer were characterized by ultraviolet absorption spectrometer and fluorescence spectrophotometer.The water contact angle tester was used to assess the relationship between the monomer of suberin and water content.Major achievements of this study were summarized as follows:(1)The young branches of C.yedoensis consist of epidermis,periderm,cortex,sclerenchyma,phloem,cambium,xylem and pith.The phellogen of annual C.yedoensis young branch originated from the cells under the epidermis and its meristematic cycle was from April 29 th to August 24th;Sudan III staining confirmed that the embolic time of phellem was May 9th,and the fluorescence time of phellem wall was May 14 th.On August 24 th,the number of phellem and phellem of oneyear-old C.yedoensis young branches increased the most,which were 25 and 7 layers,respectively.The layer number of phellem increased significantly in June,July and August when the rainfall was high.During the active period of phellogen(April to August),the length of phellem increased from 16.22 ?m to 45.56 ?m.And the growth was the fastest in April.From May 9th to May 14 th is the initial accumulation stage of suberin in the cell wall of phellem.On May 19 th,the relative concentration of phellem in cell wall of phellem increased rapidly,that is,suberin accumulated the fastest and the highest amount at this time.On August 19 th,the content of suberin was stable,but the relative concentration of suberin decreased and was lower than that on May 24 th.(2)The cell wall of phellem has double layer structure.The cell walls of phellems next to each other are composed of five parts: light-dark-light-dark-light.The corresponding cell wall structure is ‘ligninfied cell wall-suberized cell wall-compound middle layer-suberized cell wall-ligninfied cell wall'.Different staining methods were used to stain the phellem,and Sudan III was the best.The suberin in the cell wall was dyed red,which confirmed that the suberin mainly existed in the outermost layer of the cell wall.(3)The maximum absorption wavelength of the UV absorption spectrum of suberin grease dichloromethane solution is at 316 nm.The best absorption wavelength of suberin was 372 nm,and the maximum fluorescence intensity was 443nm;The content of total extracts from the periderm of C.yedoensis was about 19.22%.The main chemical components of periderm of C.yedoensis were lignin,cellulose,suberin and hemicellulose,and the contents were 43.88%,16.06%,14.81%and 5.73% respectively;The monomer of suberin was mainly composed of fatty acids,hydroxy fatty acids and aromatic compounds,and the relative contents were 52.91%,13.51% and 12.66%respectively.The moisture content of periderm was 29.59%,which was much lower than that of phloem(91.40%)and xylem(106.36%);The water absorption property of suberin is poor. |
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