Study On The Microstructure Of The Lignified Cells In Camellia Oleifera Shells

The timber resources are scarce in our country.The most fundamental solution is to promote timber conservation and substitution.Camellia oleifera shell reserves are abundant but have not been rationally utilized.The research and development of the non-lignified resource of C oleifera shells not only save resources but also protect the environment to a certain extent.The cell composition,morphology and arrangement of biomass materials can determine the various properties of the materials.This reseach mainly studies the microstructure of the lignified cells in the C.oleifera shell at different growth stages for improving the utilization of its added value.The main conclusions of this research are as follows:(1)The microscopic observation results show that there are mainly four types of cell tissues in the C.oleifera shells,which are stone cells,parenchyma,vessels and vascular tissue.The tissue ratio of parenchyma cells to stone cells is as high as 90%.In the process of cell development,the cell morphology of parenchyma,vessels and vascular tissue are almost the same in different sections with little morphological variability.The morphology of stone cells is more complicated,mainly concentric circles and irregular strips.By scanning electron microscopy observation,there are abundant pore structures on the stone cell wall of C.oleifera shells.The vessels have obvious thread thickening and spirally attached to the cell wall.The vascular tissue with thickened cell wall in the vascular tissue may be vessel tissue.According to the inverse relationship between the ratio of stone cells and parenchyma and the characteristics of microscopic images,it can be inferred that stone cells are transformed from parenchyma,the cell walls of parenchyma gradually thicken and deposit lignin.The analysis shows that the number of stone cells tends to be stable after about July(NO.12)in the middle stage of C.oleifera shells.(2)Observation by fluorescence microscope showed that all kinds of cells in the C.oleifera shells contain lignin,which was mainly deposited in stone cells with thick-walled tissues.The distribution of lignin in the cell tissue of C.oleifera shell is the highest concentration in the composite intercellular layer,the secondary wall inner layer S3 is the next,and the secondary wall middle layer S2 is the lowest.The fluorescence value L*is not directly proportional to the wall-cavity ratio of stone cells,and the staining effects of Wiesner and Maule methods show that the lignin will not continue to be deposited after a certain degree,but the cell morphology and size will continue to increase.The lignin concentration in the later stage of cell development is not as good as that in the early stage of development.Based on the Wiesner method,Maule method and Fourier transform infrared spectrum analysis,it can be showed that the lignin types of the cell wall of C.oleifera shells’ stone cells are mainly G-lignin and S-lignin during cell development.(3)The measurement by nitrogen adsorption method showed that there were a large number of mesopores with pore diameters centered between 2-20 nm in the C.oleifera shells at different developmental stages.The specific surface area BET value reaches its peak at the end of April(NO.5)and then drops to a stable level at the beginning of June(NO.9).Among them,June(NO.9-NO.10)was the transition point where the slit-type pores in the early stage of development were transformed to the coexistence of slit-type and ink bottle pores in the later stage of development.During this period,the number of stone cells were abundant,and a large amount of lignin was deposited.Lignin randomly filled the voids between the microfibrils,which changed the pore structure and morphology.The nano-scale pores were derived from the cell wall pores of stone cells and parenchyma.These pore structures may be produced when the cellulose,lignin,and hemicellulose of the cell wall were combined.The mercury injection test showed that there were still a large number of macroporous pores in the C.oleifera shells at different development stages,and the change trend of the macropore diameter was:in the early stage of the development of the C.oleifera shells,the pore size is larger,and the macropore pore size decreases in the later stage.The large pore diameter tends to be stable.The measured macroporous pores may originate from the pores with larger pores in the process of the three elements on the stone cell and parenchyma cell walls,or from the pores on the stone cell wall and the smaller vessels in the shells.