| Parenchyma is of great significance to the commercial value,utilization range and service life of Taxodiaceae,but there are great differences among species,so it is necessary to carry out comparative study on this.In this paper,Metasequoia glyptostroboides,Cryptomeria fortunei,Cunninghamia lanceolata and Taxodium ascendens,which are 4 common genera in Taxodiaceae,are used as the research objects.Quantitative and qualitative research is conducted on parenchyma and ray tissue,in order to find out the differences between species and species variability,and provide support for material evaluation and scientific and rational use.The specific results are as follows:(1)In terms of longitudinal parenchyma,the order of parenchyma cell diameter,lumen diameter and double wall thickness of 4 species was Pond Cypress > Dawn Redwood >Chinese Fir > Chinese Cedar.The mean diameters were 33.02 μm,30.96 μm,28.67 μm,25.23 μm,respectively.The average lumen diameters were 29.28 μm,27.15 μm,25.20 μm,22.01 μm,respectively.The average double wall thicknesses were 3.74 μm,3.70 μm,3.47μm,3.22 μm.The longitudinal parenchyma cell diameters,lumen diameters and double wall thicknesses of the 4 kinds of wood showed a general trend of increasing in radial direction,with great fluctuation in radial direction.From the base,the cell diameter and lumen diameter of Dawn Redwood and Pond Cypress increased slightly,while the cell diameter and lumen diameter of Chinese Cedar and Chinese Fir decreased slightly.It showed that the influence of age effect was greater than that of efficiency response.(2)The average height of longitudinal parenchyma cells of Dawn Redwood,Chinese Cedar,Chinese Fir and Pond Cypress were 139.19 μm,181.68 μm,163.54 μm and 156.50μm,respectively;The mean quantity of longitudinal parenchyma was 10,9,10 and 10,respectively.Radially,the number of longitudinal parenchyma cells increased first and then decreased.The radial variation of longitudinal parenchyma cell height of Chinese Fir and Pond Cypress was opposite to the number,while that of Chinese Cedar was the same.Axially,the number of cells in the longitudinal parenchyma of 4 Taxodiaceae species generally increased;The longitudinal parenchyma cell height of Dawn Redwood decreased continuously,that of Chinese Cedar increased first and then decreased,and that of Chinese Fir is fluctuated and decreased.The longitudinal parenchyma cell height of Dawn Redwood was basically unchanged from 0.3 to 3.3 m,and then decreased when it reached the maximum at 5.3 m.There were significant differences in longitudinal parenchyma cell height and number in radial direction,axial direction and among species.(3)The average height of wood rays of Dawn Redwood,Chinese Cedar,Chinese Fir and Pond Cypress were 141.65 μm,126.57 μm,158.37 μm and 149.48 μm,respectively;The average width was 16.16 μm,14.05 μm,16.01 μm and 17.63 μm in order.The average ray shape factors were 0.13,0.12,0.12 and 0.14,respectively.Radially,the range of ray height of Chinese Cedar and Pond Cypress was small,and the age of trees had no obvious influence on them.The ray widths of 4 Taxodiaceae species varied significantly.The radial variation of ray shape factor of Chinese Cedar was not significant,but the radial variation of ray shape factor of Dawn Redwood,Chinese Fir and Pond Cypress was significant.The ray height of the 4 species of Taxodiaceae increased from the base upward first,then fluctuated to 1.3 m.The axial variation of ray height was not significant in Dawn Redwood,but significant in the other 3 species.Axial direction,the ray width of Dawn Redwood remained unchanged,but the variation was not significant.Chinese Cedar,Chinese Fir and Pond Cypress showed a trend of decrease first and then increase,with significant variation.The axial variation of ray shape factor of 4 Taxodiaceae species decreased first and then increased,but the axial variation of Chinese Fir was not significant,while that of other 3 Taxodiaceae species was significant.(4)The longitudinal parenchyma ratio of Chinese Fir was the largest,while the ray ratio of Pond Cypress was the largest.In radial direction,the proportion of longitudinal parenchyma of Dawn Redwood,Chinese Cedar and Pond Cypress fluctuated slightly,while that of Chinese Fir increased first and then decreased.The ray tissue ratio of the 4 species showed a decreasing trend.In the axial direction,the variation range of longitudinal parenchyma ratio was smaller than that in the radial direction,indicating that the influence of tree age on the ratio was higher than that of trees.The ray tissue ratio showed certain fluctuation.(5)The heartwood extracted contents of Dawn Redwood,Chinese Cedar,Chinese Fir and Pond Cypress were 3.69%,4.58%,4.32% and 5.35%,respectively,and the sapwood extracted contents were 0.68%,0.56%,1.00% and 1.02%,respectively.There were significant differences in the heartwood extract contents of the 4 Taxodiaceae species at different heights,while in sapwood,only Dawn Redwood had significant differences,while the sapwood extract contents of Chinese Cedar,Chinese Fir and Pond Cypress had no significant differences.(6)In the heartwood,the main components of the extracts from Dawn Redwood,Chinese Cedar,Chinese Fir and Pond Cypress were alcohols,and the relative contents were 22.66%,14.28%,62.44% and 40.80%,respectively.The main components of odor were alkenes,and their relative contents were 67.17%,39.66%,62.44% and 23.80%,respectively.In sapwood,the main components of the extracts from Dawn Redwood,Chinese Cedar,Chinese Fir and Pond Cypress were alcohols and esters.The relative contents of alcohols were 38.37%,31.73%,30.24% and 35.05%,respectively,and the relative contents of esters were 35.26%,2.85%,49.20% and 33.11%,respectively.The main odor components of Dawn Redwood were esters,and the relative content was 12.99%.Chinese Cedar and Pond Cypress were mainly alkenes with relative contents of 19.06% and 32.46%,respectively.Chinese Fir contains a lot of alcohols,accounting for 31.34%.(7)Among the 4 Taxodiaceae species,there were the most similar parenchyma characteristic parameters in Chinese Fir and Pond Cypress,and Chinese Cedar was far related to the other 3 Taxodiaceae species. |
PDF Full Text Request