The dynamic changes in the distribution of lignin and hemicelluloses (xylans and xyloglucans) in cell walls during the differentiation of secondary xylem in Eucommia ulmoides Oliv. were studied by means of ultraviolet...The dynamic changes in the distribution of lignin and hemicelluloses (xylans and xyloglucans) in cell walls during the differentiation of secondary xylem in Eucommia ulmoides Oliv. were studied by means of ultraviolet light microscopy and transmission electron microscopy combined with immunogold labelling. In the cambial zone and cell expansion zone, xyloglucans were localized both in the tangential and radial walls, but no xylans or lignin were found in these regions. With the formation of secondary wall S-1 layer, lignin occurred in the cell corners and middle lamella, while xylans appeared in S-1 layer, and xyloglucans were localized in the primary walls and middle lamella. In pace with the formation of secondary wall S-2 and S-3 layer, lignification extended to S-1, S-2 and S-3 layer in sequence, showing a patchy style of lignin deposition. Concurrently, xylans distributed in the whole secondary walls and xyloglucans, on the other hand, still localized in the primary walls and middle lamella. The results indicated that along with the formation and lignification of the secondary wall, great changes had taken place in the cell walls. Different parts of cell walls, such as cell corners, middle lamella, primary walls and various layers of secondary walls, had different kinds of hemicelluloses, which formed various cell wall architecture combined with lignin and other cell wall components.展开更多
The developmental process of oil cells in the shoot of Litsea pungens Hemsl. has been studied with transmission electron microscopy. According to the development of the three layers of cell wall, the developmental pro...The developmental process of oil cells in the shoot of Litsea pungens Hemsl. has been studied with transmission electron microscopy. According to the development of the three layers of cell wall, the developmental process could be divided into 4 stages. In stage 1, the cell wall consisted only of a primary (the outmost) cellulose layer, which might further be divided into two substages, the oil cell initial, and the vacuolizing oil cell. During this stage, there were some small electron translucent vesicles and dark osmiophilic droplets of variant sizes in the different-shaped plastids. It was observed that some dark and gray osmiophilic materials coalesced to vacuoles in the cytoplasm. In stage 2, a lamellated suberin layer accumulated inside the primary cellulose layer. In stage 3, a thicker and looser inner cellulose wall layer was formed gradually inside the suberin layer. Some dark osmiophilic droplets have been observed in this loose inner cellulose wall layer. The plasmodesmata were blocked up and became a special structure. Then, the big vacuole, which is the oil sac, was full of osmiophilic oil. In stage 4, the oil cell became matured and the cytoplasm disintegrated. The oil sac enveloped from plasmalemma was attached to the cupule, which was formed by the protuberance of the inner cellulose wall layer into the lumen. After the maturity of oil cell, the ground cytoplasm began to disintegrate and became electron opaque or exhibited in a disordered state, and the osmiophilic oil appeared light gray.展开更多
The penetration modeling of an adhesive into the fiber requires the measurement of various properties of resin and fiber： the resin viscosity, its surface tension, the penetration depth and the timber pore radius. Th...The penetration modeling of an adhesive into the fiber requires the measurement of various properties of resin and fiber： the resin viscosity, its surface tension, the penetration depth and the timber pore radius. This study is based on the screening technique that identifies the factors sensed by the experimenter. In order to determine the optimum processing conditions and find the combination of parameters that maximize the productivity in the experimental phase, a geometric illustration of the response has been made. The results are： the pores radius （4 μm）, surface tension （62.5 mN/m）, depth （10 μm） and viscosity （2,000 Cp）.展开更多
Fractal theory was introduced in order to describe the ultrastructure of wood cell wall in this paper. The cellulose chain clusters around nano-scale were viewed as a fractal object that consists of many fibrillar str...Fractal theory was introduced in order to describe the ultrastructure of wood cell wall in this paper. The cellulose chain clusters around nano-scale were viewed as a fractal object that consists of many fibrillar structural units with different scales including microfibrils. On the basis of the morphological data of wood cell wall, fractal dimensions of multi-level fibrillar structural units were calculated by fractal-geometry approach, and then the morphological and structural characteristics of fibers as well as the influences on wood properties were investigated according to the dimensions. Besides, the fractal self-nesting character of the ultrastruture was also analyzed.展开更多
文摘The dynamic changes in the distribution of lignin and hemicelluloses (xylans and xyloglucans) in cell walls during the differentiation of secondary xylem in Eucommia ulmoides Oliv. were studied by means of ultraviolet light microscopy and transmission electron microscopy combined with immunogold labelling. In the cambial zone and cell expansion zone, xyloglucans were localized both in the tangential and radial walls, but no xylans or lignin were found in these regions. With the formation of secondary wall S-1 layer, lignin occurred in the cell corners and middle lamella, while xylans appeared in S-1 layer, and xyloglucans were localized in the primary walls and middle lamella. In pace with the formation of secondary wall S-2 and S-3 layer, lignification extended to S-1, S-2 and S-3 layer in sequence, showing a patchy style of lignin deposition. Concurrently, xylans distributed in the whole secondary walls and xyloglucans, on the other hand, still localized in the primary walls and middle lamella. The results indicated that along with the formation and lignification of the secondary wall, great changes had taken place in the cell walls. Different parts of cell walls, such as cell corners, middle lamella, primary walls and various layers of secondary walls, had different kinds of hemicelluloses, which formed various cell wall architecture combined with lignin and other cell wall components.
文摘The developmental process of oil cells in the shoot of Litsea pungens Hemsl. has been studied with transmission electron microscopy. According to the development of the three layers of cell wall, the developmental process could be divided into 4 stages. In stage 1, the cell wall consisted only of a primary (the outmost) cellulose layer, which might further be divided into two substages, the oil cell initial, and the vacuolizing oil cell. During this stage, there were some small electron translucent vesicles and dark osmiophilic droplets of variant sizes in the different-shaped plastids. It was observed that some dark and gray osmiophilic materials coalesced to vacuoles in the cytoplasm. In stage 2, a lamellated suberin layer accumulated inside the primary cellulose layer. In stage 3, a thicker and looser inner cellulose wall layer was formed gradually inside the suberin layer. Some dark osmiophilic droplets have been observed in this loose inner cellulose wall layer. The plasmodesmata were blocked up and became a special structure. Then, the big vacuole, which is the oil sac, was full of osmiophilic oil. In stage 4, the oil cell became matured and the cytoplasm disintegrated. The oil sac enveloped from plasmalemma was attached to the cupule, which was formed by the protuberance of the inner cellulose wall layer into the lumen. After the maturity of oil cell, the ground cytoplasm began to disintegrate and became electron opaque or exhibited in a disordered state, and the osmiophilic oil appeared light gray.
文摘The penetration modeling of an adhesive into the fiber requires the measurement of various properties of resin and fiber： the resin viscosity, its surface tension, the penetration depth and the timber pore radius. This study is based on the screening technique that identifies the factors sensed by the experimenter. In order to determine the optimum processing conditions and find the combination of parameters that maximize the productivity in the experimental phase, a geometric illustration of the response has been made. The results are： the pores radius （4 μm）, surface tension （62.5 mN/m）, depth （10 μm） and viscosity （2,000 Cp）.
文摘Fractal theory was introduced in order to describe the ultrastructure of wood cell wall in this paper. The cellulose chain clusters around nano-scale were viewed as a fractal object that consists of many fibrillar structural units with different scales including microfibrils. On the basis of the morphological data of wood cell wall, fractal dimensions of multi-level fibrillar structural units were calculated by fractal-geometry approach, and then the morphological and structural characteristics of fibers as well as the influences on wood properties were investigated according to the dimensions. Besides, the fractal self-nesting character of the ultrastruture was also analyzed.
