Broken Cell Walls Research Articles

Effect of Drying on Microstructure of Plant Tissue

Drying causes many chemical and physical changes in plant tissue. Physical changes are mostly due to stresses developed in the tissue and are pronounced by macro- and microalterations of size, shape and internal structure. The extent and direction of these changes depend on the mode of drying. Convective drying of apple tissue results in numerous breaks of cell walls and formation of many microcavities. In consequence, the dominating cross-sectional area of cells moves toward values smaller than those observed in raw apple. Cavities formed during convective drying can be pictured in 2D plane as pentagons joined together or ellipses with large ratio between axes. Puff-drying forms porous structure with cavities twice as large as in raw apple. The process homogenizes the structure, and spread of cell sizes is even smaller than that observed in raw apple. Broken cell walls are clearly visible in microphotographs of sliced samples. Many large cavities with cross-sectional area exceeding 40,000 µm2 are characteristic of puff-dried apple while such areas are hardly found in raw apple. The structure of freeze-dried apple is similar to that formed during puff-drying. Large irregular cavities and broken cell walls are clearly seen in microphotographs. However, larger cavities are present in freeze-dried apple than in puff-dried one. Cross-sectional area of cavities in freeze-dried apple can be simulated by pentagons joined together or elongated ellipses.

Failure of Fertilization Associated with Absence of Zygote Development in the Interspecific Cross of Fagopyrum tataricum * F.esculentum.

To obtain a desirable hybrid from an interspecific cross between Fagopyrum tataricum and F. esculentum, the early embryo developmental changes were investigated by light microscopy and transmission electron microscopy (TEM). The nature of pre- and post-fertilization barriers in the hybrid embryo was examined at the ultrastructural level. The ovules were excised at 1 to 5 days after pollination (DAP) and fixed for TEM. In comparison with self-pollinated embryo (F. tataricum) or legitimate-pollinated embryo (F. esculentum), the interspecific hybrid embryos showed numerous abnormal ultrastructural pre- and post-fertilization phenomena leading to the abortion of embryo. The main abnormal phenomena were failure of fertilization, no zygotic development with a broken cell wall, dispersed endosperm with absence of ribosomes, and defective embryo sac development such as srunken, small and irregular-shaped embryo sac. The interspecific incompatibility was attributed to the failure of fertilization and the hybrid zygotic embryo showed retardation in cell division, which resulted in cease of development.

227 異種物質内包クローズドセル構造金属材料の圧縮による破壊特性(OS 多機能・複合機能化への材料協調設計)

Powder particles of polystyrene coated with nickel-phosphorus alloy layers using electroless plating were pressed into pellets by isostatic pressing and sintered in vacuum at high temperature. A metallic closed cellular material was then fabricated. The compressive tests of this metallic closed cellular material containing organic materials were performed. The obtained results show that this material has the different stress-strain curves among the specimens that have different thickness of the cell walls. Also these results show this closed cellular material has a long plateau region in the curves and high energy absorption. The cracks occur in the direction parallel to the loading axis in the plateau region and the broken cell walls were observed on the fracture surface. It should be thought that the fracture of cell walls causes this high energy absorption.

Microscopic Examination of Chilling Injury Symptoms in Ethanol-treated Cucumber Seedling Roots

Cucumber seedlings were germinated for 24 h at 25 °C and half were immersed in a 500 mM ethanol solution for 2 h. After rinsing, seedlings were chilled for 96 h at 2 °C. Control and ethanol-treated samples were taken for light and electron microscopy immediately before and after chilling, and after re-warming for 24 and 72 h. Preliminary experiments revealed visual chilling symptoms such as pinching of the root in a region just above the root tip. This region was excised under a microscope, fixed, and mounted for microscopic observations. The cortical cells of ethanol-treated seedlings before chilling appeared to be irregular in shape with irregular edges, and some epidermal damage was evident. Chilling caused much more epidermal damage in the control seedlings when compared to the ethanol-treated seedlings. After chilling, cortical cells in the control seedlings were observed to be irregularly shaped while those treated with ethanol had round cells. Upon re-warming, control seedlings exhibited increasing epidermal damage with broken cell walls, while ethanol-treated seedlings exhibited more differentiation in the stele.

Lead uptake, localization and changes in cell ultrastructure ofFunaria hygrometrica protonemata

The main sites of lead entering the protonemata were spores with broken cell walls and apical cells of protonemata. The lead ions could enter the symplast probably by endocytosis but we can not exclude diffusion as the way of entering. Lead deposits inside a protoplast were observed after 2 h of lead application. After 12 h, Pb deposits were commonly present in all cell structures surrounded by a membrane. Some disturbances in ultrastructure of organelles were found after 8 h. The most frequent were: change of endoplasmatic reticulum configuration from linear to concentric one in many cases surrounding other organelles (e.g. mitochondria) and large and numerous plastoglobuli in chloroplasts. Longer treatment of protonemata with lead (24 h or 48 h) caused degeneration of organelles and even death of the cell.

EXTRUDED CORN GRITS?QUINOA BLENDS: II. PHYSICAL CHARACTERISTICS of EXTRUDED PRODUCTS

Quinoa was blended with corn grits at levels of 10%, 20% and 30% and extruded at 15% and 25% moisture respectively, using screws with a 1:1 or 3:1 compression ratio. Extrusion temperatures were 80° and 100°C at the feed section and 100° or 150°C at the compression section, respectively. RPM values were 100, 150 and 200. Quinoa addition produced a darker, less yellow product than corn grits alone. Density, expansion ratio and shear strength were lower for products containing greater levels of quinoa. the most favorable products were produced at a 15% initial moisture content and a 3:1 compression ratio. Products extruded under these conditions had the greater expansion, lower density and lower shear strength than products extruded at 25% moisture or at a 1:1 compression ratio. SEM showed larger, more uniform cells in the 100% corn grits product indicating a more even expansion. A product containing 30% quinoa had a rougher texture, many broken cell walls and less evenly distributed air cells.

Adhesion of cellulose to cell walls toTrichoderma reesei

Abstract The attachment of Trichoderma reesei QM 9414 cell wall fractions to cellulose crystallites from cotton fibres was simulated under conditions of isopycnic density gradient centrifugation. Cell wall fractions were obtained from mechanically sheared mycelia of cellobiose-grown Trichoderma cultures. Diameters of broken cell wall portions were 1–4 μm. Cellulose crystallites (length: 400–1 000 nm, width: 60–100 nm) were prepared from dewaxed cotton fibres using a cellulase-complex with free-fibre forming characteristics. The hydrolase complex was isolated from culture fluid of cellulose-grown Trichoderma reesei . The hydrolase has endo- and exoglucanase activities. The structural properties of the cellulose crystallites observed by TEM are given. Mixing cellulose crystallites ( d = 1.135 g/ml) with cell wall fractions ( d = 1.080 g/ml) resulted in a hybrid band with an intermediate density of 1.105 g/ml after density gradient centrifugation. This indicates a strong binding between both components. The mode of binding cellulose to cell walls is discussed.