Stduy On Cell Morphological Characteristics Of Tissue Cell And Variation Regularity Of Cell Wall Lignin Of C3H RNAi Transgenic Poplar

Lignin genetic engineering can effectively reduce the lignin content of the cell walls in poplars,and improve utilization characteristic of poplars as the lignocellulosic material.However,the influence of lignin genetic engineering on morphological characteristics of the tissue cells and lignin distribution at micro-area of transgenic poplars also show important research significance.In this paper,C3 H down-regulated transgenic Populus alba×P.glandulosa cv`84k’ and non-transgenic poplar were selected.The optical and electron microscopes were used to observe the differences of cell morphology and morphological parameters of fibers and vessels of two kinds of poplars.The Acetyl bromide method(AcBr),Pyrolysis–gas-chromatography/mass spectrometry(Py-GC/MS)and Fourier transform infrared(FTIR)were used to determine the content and structure of lignin and other key cell wall chemical components of transgenic poplars.The histochemistry reaction and Confocal laser scanning microscopy(CLSM)and Raman microscopic analysis were used to observe micro-distribution of lignin and polysaccharide in situ atcell walls of transgenic poplars.The main results of this paper were as follows:1.Morphological characteristics of tissuecells of transgenic poplars(1)Transgenic poplarswere typical diffuse-porous woods.The vessels,fibers and ray tissue cells all showed similar distribution rule from pith to bark with the control groups.It was also found that the shape of the vessel walls of the transgenic poplarswere wavy,and there were some differences compared with the shape like ellipse of control groups.(2)The average wall thickness of transgenic poplars fibers(2.17μm)was lower than that of control group(2.42μm),with an average reduction of 12.40%.The fibers length of transgenic poplar woods(0.551mm)was raised compared with that of the control group(0.526mm),with an average increment of 4.75%.And the values of fiber cell wall thickness and fiber length of the two kinds of poplars were increased with the lignification degree increasing.There were no significant differences in fiber lumen diameter and width between transgenic poplars(11.95μm,21.1 μm)and the control group(11.65μm,22.5 μm).Compared with control group,the ratio of fiber cell wall thickness to the lumen diameter of transgenic poplar wood wall were decreased.(3)The vessel wall thickness of transgenic poplars(1.92μm)was thinner than that of control poplars(2.12μm),with an average of 9.43%.There was no significant difference in the longitudinal heights of transgenic poplars vessel wall thickness.There was also no significant differences in mean value of the lumen diameter between transgenicpoplar(32.21μm)and control group(32.04μm).Compared with the control group,the ratio of the vessel wall thickness to the lumen diameter of transgenic poplar was decreased.2.Lignin content and composition of transgenic poplars(1)The main chemical components composition in the cell wall of transgenic poplars were consistent with that of the control groups.But the content of lignin in the cell wall of transgenic poplar(25%)was lower than that of control group(29.3%).The value of lignin content at different heights of transgenic poplar showed a down-regulated trend,and with an average reduction of 14.68%.The relative content of cellulose and hemicellulose of transgenic poplar were increased compared with that of its control.(2)The relative content of G and S lignin monomer of transgenic poplars decreased while the H monomer content increased,compared with the control.The relative contents of G,S and H of the transgenic poplar trees were 30.85%,54.69% and 12.13%,and the control group were 34.39%,59.42% and 6.19%,respectively.There was no significant difference in the composition of G and S lignin monomers of the two kinds of poplars,but the H monomer composition of transgenic poplarswere increased.3.Lignin and polysaccharides micro-distribution of transgenic poplars(1)The G lignin monomer of transgenic poplar was evenly concentrated at vessel wall,while S lignin monomer was uniformly distributed in fiber cell walls.The lignin distribution at the cell wall micro-area and radical direction of transgenic poplars were that the concentration at cell wall corner was greatestand followed by the cell wall middle lamellar and second cell wall,and lignin showed higher depositional concentration near the pith than that in middle position of xylem,and there were no significant differences between transgenic poplars and control poplars.(2)The polysaccharides of transgenic poplars were mainly concentrated in the second cell wall and the cell wall middle lamellar,while there was lessconcentration at the cell corner.And it was found that the polysaccharides concentration at the same micro-area of transgenic poplars showed higher concentration than that of control poplars,indicating that the polysaccharide content of transgenic poplar was increased after the lignin content down-regulated.