麦秆不同形态区域中硅的碱稳定性

用SEM-EDAX法研究麦草原料中的Si在碱法制浆过程中的残留情况.结果表明,在碱法制浆过程中,麦秆外表面皮层及皮下纤维层中的Si对碱的稳定性较差,麦秆内部的维管束及内表皮层中Si的碱稳定性较高;原料的Si脱除率仅为60%～70%,浆中残留的Si量为30%～40%,且主要分布在麦秆内部的细胞中.不同部位中Si的碱稳定性不同意味着Si等矿质元素存在的化学状态的差异.     

Texture of frozen vegetables: Effect of freezing rate on green beans

The texture of green beans after blanching, freezing and cooking was measured with a shear press. Each processing step reduced shear resistance about the same amount. Visible damage to the vegetable tissues was caused by freezing, but not by blanching or cooking. Very rapid freezing by immersion in liquid nitrogen prevented damage and reduced the texture degradation. When the freezing rate was slightly slower than that required for perfect preservation, immature cells of the inner parenchyma were the first to be damaged. Further reduction of the freezing rate caused breakage of other cell walls in this tissue, and separation of walls in the outer part of the pod. When the freezing rate was changed during freezing, the part of the bean that froze rapidly was not damaged, whereas that which froze slowly was damaged. Decreasing the freezing rate during freezing did not damage the portion of the bean already frozen. Sensory appraisal panels were able to distinguish texture differences in beans frozen at various rates when there were visible differences in the amounts of cell wall damage.     

Isolates of cell types from sorghum stems: Digestion,cell wall and anatomical characteristics

Cell types were separated from internode 5 of sorghum stems to study the interrelationship between digestion characteristics and cell wall composition. Isolates of epidermis (EPI), sclerenchyma (SCL), vascular bundle zone (VBZ), inner vascular bundles (IVB) and pith parenchyma cells (PITH) were freeze-dried and ground for analysis. The cell fractions were digested in rumen fluid for times between 0 and 96 h, and wall composition measured using detergent extraction procedures. In-vitro dry matter digestibility (g kg^?1 after 48 h) of cell fractions was in the order of PITH (849-906) > IVB (794-816) > SCL (692-701) > VBZ (641-679) > EPI (608-628). Total cell wall content (CWC), indigestible CWC, and lignin content followed the inverse order. Lignin concentration on a dry matter or cell wall basis was highly correlated with indigestible wall residue after 96 h. The proportion of cell wall digested after 96 h was higher for SCL and VBZ cells (61·8-68·2%) than for PITH cells (48·4-56·1 %), despite the former having lignin content three to five times higher than that of PITH cells. Clearly, there were differences between the cell types in wall composition or chemical linkages between wall components that lead to the observed differences in wall digestion.     

Microspectrophotometric characterization of aromatic constituents in cell walls of hard and soft wheats

Cell walls of epidermis, hypodermis, nucellar epidermis, aleurone, and endosperm in hard and soft wheat (Triticum aestivum L) kernels were evaluated for aromatic constituents using ultraviolet (UV) absorption microspectrophotometry. Wheat varieties sampled were soft red winter Caldwell, hard red winter varieties Tam 200 and Karl, and hard red spring varieties Len and Yecora rojo. Spectra of cell walls of epidermis and hypodermis (beeswing cells) suggested larger amounts and a greater degree of polymerization of aromatic constituents in these walls compared to those of other cell types. Results also suggested the presence of ester-linked ferulic acid. Nucellar epidermal walls also had polymerized aromatics and ferulic acid, but amounts appeared to be much less than in the walls of the beeswing cells. UV spectra of aleurone walls suggested that the predominant aromatic was ester-linked ferulic acid; anticlinal walls had substantially more aromatic constituents than outer or inner periclinal walls. Endosperm walls lacked any indication of aromatics by this method. Grain hardness did not appear to be related to cell wall aromatics. UV absorption microspectrophotometry indicated significant variations in wall aromatics of different cell types of wheat grains.     

Preparation and composition of mesophyll,epidermis and fibre cell walls from leaves of perennial ryegrass (lolium perenne) and italian ryegrass (lolium multiflorum)

Cells of mesophyll, epidermis and residual fibrous material were obtained from leaves of Italian and perennial ryegrass harvested at different stages of maturity by mechanical disruption of leaf tissue. Mesophyll cells were selectively removed by filtration through 0.045 mm nylon mesh and remaining non-mesophyll cells centrifuged in metrizamide solutions (56–58% wt to vol.) of known density (1.308–1.329 g cm³ at 5°C) to obtain a pure epidermis cell fraction and a residual fibre fraction. Whole mesophyll cells contributed 63–72%, epidermis 12–15% and the fibre fraction 15–24% to the total leaf dry matter. Fibre values were higher in late-cut samples. Cell walls were prepared from mesophyll and epidermis cells by disruption and washing to remove cell contents. Fibre cells were judged free of cell contents and received no further treatment. Examination of cell wall preparations by light and electron microscopy showed that both mesophyll and epidermis preparations were essentially free from contaminating material. Mesophyll cell walls were uniformly thin (200 nm) while those of epidermis ranged from 2000–3000 nm at the outer face, thinning to 300 nm or less at the inner surface. An electron-light layer (cuticle) of approximately 200 nm thickness was present covering the outer face of the epidermis. The fibre fraction largely consisted of sclerenchyma, but contained, in addition, other vascular cells, detached annular rings and heavily silicified leaf hairs. Analysis of cell walls accounted for 85–90% of dry matter. Cellulose was the major component of all cell walls examined (approximately 40% of dry matter) with xylose residues accounting for a further 11% of mesophyll, 13.5–17.5% of epidermis and 21–25% of fibre cell walls. Arabinose was low in fibre cells but was present in much higher proportions in mesophyll and epidermis walls. The ratio of arabinose to xylose was approximately 1:1.5 for mesophyll, 1:2.5 for epidermis and 1:7.0 for the fibre fraction. The molar ratio acetyl to xylose remained fairly constant at 1:4 regardless of the grass, cell type or maturity of the sample. The uronic acid content of epidermis was higher than that in other cell types and showed an increase with increasing maturity of the grass, reaching over 9% in late-cut samples. Total phenolic material represented 2–3% of mesophyll and epidermis cell walls and 6% of fibre walls. Ferulic acid alone was released from the primary cell walls by saponification and p-coumaric and ferulic acids from the secondary-thickened fibre walls. Crude protein values (NX6.25) were high in mesophyll cell wall preparations and low in epidermis and fibre cell walls. Amino acid patterns were similar for both grasses and cell types but hydroxyproline was found in greater amounts in fibre cell walls than in either epidermis or mesophyll.     

Phenolic acids released from bermudagrass (Cynodon dactylon) by sequential sodium hydroxide treatment in relation to biodegradation of cell types

Sections of solvent-extracted bermudagrass (Cynodon dactylon L Pers) leaf blades were treated sequentially with increasing concentrations of sodium hydroxide. The amounts of saponifiable phenolic acid monomers and cyclobutane dimers released and the digestibility of the treated blades (ie % dry weight loss) were determined. Leaf sections were examined by scanning electron microscopy for biodegradation of cell types and histochemically (light microscopy) for lignin after treatment with sodium hydroxide. Treatment with 0.1 m sodium hydroxide for 1 h resulted in only minor changes from untreated sections. However, this treatment for 24 h released 86% of the ferulic acid, 65% of the dimers, and c 50% of the p-coumaric acid. Digestibility was increased from 6.5% in the untreated control to 56.6%. Substantial loss of the slowly biodegradable tissues (ie epidermis and parenchyma bundle sheath) and partial biodegradation and disruption of the refractory tissues (ie sclerenchyma, xylem and mestome sheath) occurred; histochemical reactions for lignin were less intense after NaOH treatment. Treatment with 1 m sodium hydroxide for 24 h released 50% of the p-coumaric acid and the remainder of the alkali-extractable ferulic acid and dimers, increased digestibility to 72%, and increased biodegradation of mesophyll and phloem. Mestome sheath cell walls only gave a histochemical reaction for phenolics and the reaction was weak after 1 m NaOH treatment. Alkali treatment increased the biodegradation of all cell types, with lignified tissues reduced to single-cell fibres after 1 and 2 m treatments.     

Formation and deposition of tannins in Quebracho colorado (Schinopsis balansae Engl.)

In Quebracho colorado heartwood tannins are located in the lumina of most parenchyma cells, fibres and vessels. Formation and deposition of the tannins were studied by electron microscopy. In parenchyma cells phenolic compounds first occur at the inner and outer side of the membranes of vacuoles. Later, these vacuoles are completely filled with dark stained compounds and fuse together. From parenchyma cells the phenolic substances migrate into the lumina of fibres and vessels through pits. In pits they penetrate into the compound middle lamella (CML) and diffuse along the CML. Tannins were also found in the cell walls and in fissures within the CML and G-layer of tension wood fibres.     

Effect of tissue type and variety on cell wall chemistry of onion (Allium cepa L.)

The purpose of this study was a comparative examination of the cell wall chemistry of component tissues of different varieties of onions (Allium cepa L. cv Sturon, Durco, Hysam, Grano de Oro and Caribo). Cold alcohol-insoluble residues (CAIRs) were prepared and were extracted sequentially with water, imidazole, CDTA, Na₂CO₃ and 0.5 M KOH to leave a residue. These were analysed for their carbohydrate compositions. On a whole organ basis, the cell wall carbohydrate composition was similar for each variety studied, and no significant change resulted from commercial storage, with or without sprout suppressant. However, there were significant differences in the carbohydrate composition of cell walls from different tissues. Cell walls of inner leaf bases contained galactoserich pectic polysaccharides. Outer layers had progressively less pectic galactose, and the outer brown skin contained virtually none. This was accompanied by changes in water- and CDTA-soluble polysaccharides and may be related to the dry and protective nature of the non-lignified outer skin. The differences in cell walls from different tissues provide the basis for developing processing methods for exploiting onion waste.     

Composition of cell walls isolated from cell types of grain sorghum stems

Cell types were isolated from sorghum stems at two stages of development, anthesis and grain maturity, to study cell wall characteristics. Cell walls were isolated from epidermis (EPID), sclerenchyma (SCL), vascular bundle zone (VBZ), inner vascular bundles (IVB) and pith parenchyma cells (PITH) and analysed for total carbohydrate, acid insoluble lignin, total uronosyls, neutral sugars and hydroxycinnamic acids. In addition, walls from SCL, VBZ, IVB and PITH were subjected to chemical fractionation to separate wall carbohydrate into polysaccharide groups. Although wall characteristics were similar at both plant maturities, there were differences in lignin concentration, hydroxycinnamic acids, and carbohydrate composition among the cell wall types. Lignin was lowest in the PITH walls (169 g kg⁻¹) and highest in SCL and EPID (c 211 g kg⁻¹). Cellulose was most abundant in VBZ and SCL walls with greater secondary wall formation. Pectic materials were most abundant in PITH walls. Xylans were similar among wall types except for EPID that contained higher amounts of xylose. Releasable hydroxycinnamates were not as consistent among the cell wall types. Total ferulates, including ester linked and releasable ether linked, tended to increase from PITH to SCL (8 to 15 g kg⁻¹ CW) with an increase in the proportion etherified within the wall matrices (PITH 51%; SCL 66%). Total p‐coumarates showed opposite trends with PITH walls having significantly more (35 g kg⁻¹ CW) than VBZ or SCL (19 and 13 g kg⁻¹ CW). EPID walls contained the least pCA (6.5 g kg⁻¹ CW). Except for the hydroxycinnamates, compositional trends for the different wall types would reflect changes from primary walls to increased amounts of secondary wall. Neutral sugar analysis of indigestible residues indicated similar carbohydrate compositions among the cell wall types, with xylose being less degradable than all other wall sugars. © 1999 Society of Chemical Industry     

FREEZE-THAW (AND BLANCH) DAMAGE TO VEGETABLE ULTRASTRUCTURE

The parenchyma cells of three vegetable tissues varying in starch content as well as in textural response to freeze-thawing were studied ultrastructurally before and after controlled freeze-thaw regimes. Similar tissue samples were also studied after blanching and after the blanch-freeze-thaw combination. Subcellular structures were altered more drastically by blanching than by freeze-thawing. There was much less fine structural disruption in the high starch tissue (green pea cotyledon) than in the tissues of lower starch content (spinach leaf and green bean pod) following all processing treatments. As judged by sensory evaluation, peas also underwent less textural change on processing than the other tissues studied. The minimal ultrastructural change observed in peas may be associated with certain cell characteristics: high starch content, abundant protoplasmic structure, and resultant low degree of vacuolation. It is concluded that - of these - the starch granule component is the major contributor to texture. This probably applies in the case of most processed vegetable tissues of relatively high starch content. The protective role of cellular starch is discussed in relation to fine structure retention and to texture.     

甜菜丛根病根部形态解剖学观察

对甜菜丛根病病根进行解剖学观察研究，结果表明：根部结构发生较大变化，（1）根的周皮结构发生异常，周皮表面不光滑，细胞排列不规则，有的凸凹不平，有的产生裂口，有的细胞脱落，细胞壁褐化等。（2）根维管束异常，导管木化现象明显，导管内或周围有一些异样物质，其染色较深，尤其是初生和次生木质部这种现象更为严重。（3）维管束间的薄壁组织（结合组织）异常，近周皮附近的薄壁细胞组织破裂产生裂隙，产生染色较深的一群异样组织，木质部附近的木薄壁细胞有破损现象。     

芒秆皮层的SEM-EDXA研究(Ⅰ)

用SEM-EDXA法研究芒秆茎部皮层的形态、超微结构及矿质元素分布.结果表明,芒茎皮层外表面由纵向的条纹区和非条纹区交替排列而成;皮层纵切面中存在多孔结构及具层状细胞壁的横向管孔;皮层中存在不同结晶形态的Si化合物.芒茎皮层的形态及超微结构明显与甘蔗、麦草等的茎部皮层不同.芒茎皮层主要含C、O、Si、K等元素,Si元素含量高于50%,C元素含量低于4.0%;皮层中部的Si元素含量最高,外部及内部的Si元素含量稍低;皮下纤维及芒茎内部组织结构中的Si元素含量均为0.00%.皮层中的Si化合物主要是无机物.     

Histological and cell wall polysaccharide chemical variability among apricot varieties

The variability of histological and cell wall chemical characteristics of apricot were assessed in nine apricot varieties: Harogem, Goldrich, Hargrand, Iranien, Moniqui, Orangered^® Bhart, Stark Early Orange, Ravicille and Rouge du Roussillon. For chemical analyses, Iranien and Moniqui were harvested twice at two weeks interval and Goldrich parenchyma was subdivided into inner and outer tissue.     

DIFFERENCES IN THE STRUCTURAL RESPONSE OF 'GRANNY-SMITH' APPLES UNDER MECHANICAL IMPACT AND COMPRESSION

Apple fruits, cv. Granny Smith, were subjected to mechanical impact and compression loads utilizing a steel rod with a spherical tip 19 mm diameter, 50.6 g mass. Energies applied were low enough to produce enzymatic reaction: 0.0120 J for impact, and 0.0199 J for compression. Bruised material was cut and examined with a transmission electron microscope. In both compression and impact, bruises showed a central region located in the flesh parenchyma, at a distance that approximately equalled the indentor tip radius. The parenchyma cells of this region were more altered than cells from the epidermis and hypodermis. Tissues under compression presented numerous deformed parenchyma cells with broken tonoplasts and tissue degradation as predicted by several investigators. The impacted cells supported different kinds of stresses than compressed cells, resulting in the formation of intensive vesiculation, either in the vacuole or in the middle lamella region between cell walls of adjacent cells.     

Electron microscopic studies in cultivated plants. I. Green pods of Phaseolus vulgaris var. nanus L

Scanning (SEM) and transmission (TEM) electron microscopic studies in the legumen of Phaseolus vulgaris var. nanus L. (kidney beans) were carried out. In this work emphasis was laid on the analysis of the morphological structure of the parenchyma tissue, being the chief component of the pod at edible maturity. The leaf character of the pod becomes especially evident by the occurence of stomata, trichomes, and typical cuticle structures on the outside of the pod (SEM). The cells of the mesophyll-like parenchyma tissue are distinguished by a great range of variation of their plastids (chloroplasts--chloroamyloplasts--amyloplasts) and some special cytological features such as a strongly developed rough ER, big nuclei, and numerous plasmodesmata (TEM).     

氨纶包芯纱蠕变性能测试与分析

对大豆蛋白复合纤维、棉和涤纶纤维纺制的氨纶包芯纱的蠕变性能进行测试,基于纺织材料的黏弹性理论,使用四元素力学模型分析氨纶包芯纱的拉伸变形规律,并利用DPS数据处理系统,建立了氨纶包芯纱蠕变伸长的拟合方程,从本质上研究大豆蛋白/氨、棉/氨、涤/氨包芯纱的蠕变性能特征。结果表明:氨纶包芯纱外包纤维种类不同,其蠕变性能亦不同;四元素模型的理论分析结果比较接近实际测试值,即应用四元素模型可以较好地描述各种氨纶包芯纱的蠕变规律。     

Variations in anatomy and ultraviolet microspectrometry between normal and brown midrib mutant maizes possessing different rumen degradabilities

Normal and brown midrib mutant (bmr) maize (Zea mays L) were examined for variations in their morphological composition. The degradability of the leaf blade, leaf sheath and stem, proportional area of specific tissues in leaf blade, and the ultraviolet (UV) absorption spectra of cell walls were measured and related to variations in cell wall degradability by rumen microorganisms. The UV and infrared (IR) absorption spectra of the lignins isolated from leaf blades of both types, before and after reduction with sodium borohydride, were recorded. The bmr3 maize had higher dry matter (DM) and neutral detergent fibre (NDF) degradabilities for leaf blade, leaf sheath, and stem than the normal counterpart. Approximately 35% and 26% of the observed difference in DM degradability was attributed to the difference in DM degradability of stem and leaf blade, respectively, and 39% to the difference in DM composition of stem. Distinct differences in tissue degradation of the leaf blades were observed for mesophyll cell walls in the midrib portion, which were thinner and of greater number in the bmr3 maize. Sclerenchyma cells were present only in the vascular bundles in the bmr3 leaf blade, while in the normal type those cells were underneath the epidermis tissue. The bmr3 plant also had large epidermal cells. UV microspectrometry of mesophyll cell walls of the bmr3 maize showed their lower UV absorbance around 320 nm compared to that of the normal, but not at 280 nm. Considerable increase in the UV absorbance at 280 nm was observed for the isolated lignins after reduction, suggesting a lesser degree of lignification in the bmr3 maize tissues. Lowered UV absorbance of the isolated lignin around 320 nm after reduction was associated with the removal of the IR bands at 1730, 1660, 1600, and 1250 cm^?1.     

Foetal fibroblasts introduced to cleaving mouse embryos contribute to full-term development

Foetal fibroblasts (FFs) labelled with vital fluorescent dye were microsurgically introduced into eight-cell mouse embryos, three cells to each embryo. FFs were first identified in the inner cell mass (ICM) in about one-third of embryos, whereas in three quarters of embryos FFs were located among trophoblast cells. Some elimination of FFs from trophoblast occurred later on. Eventually, in blastocysts' outgrowths, an equally high contribution from FFs progeny (60%) was found in both ICM and trophoblast. Three days after manipulation, FFs resumed proliferation in vitro. More than three FFs were found in 46.2% of embryos on day 4. On the 7th day in vitro in 70% of embryos more than 12 FFs were found, proving at least three cell divisions. To study postimplantation development, the embryos with FFs were transferred to pseudopregnant recipients a day after manipulation. After implantation, FFs were identified by electrophoresis for isozymes of glucose phosphate isomerase (GPI). A single 11-day embryo delayed to day 8 proved chimeric by expressing both donor isozyme GPI-1B and recipient GPI-1A. Similar chimerism was found in the extraembryonic lineage of 11% of embryos by day 12. Starting from day 11 onwards, in 32% of normal embryos and in 57% of foetal membranes, hybrid GPI-1AB isozyme, as well as recipient isozyme, was present. Hybrid GPI-1AB can only be produced in hybrid cells derived by cell fusion, therefore, we suggest that during postimplantation development, FFs are rescued by fusion with recipient cells. In the mice born, hybrid isozyme was found in several tissues, including brain, lung, gut and kidney. We conclude that somatic cells (FFs) can proliferate in early embryonic environment until early postimplantation stages. Foetuses and the mice born are chimeras between recipient cells and hybrid cells with contributions from the donor FFs. Transdifferentiation as opposed to reprogramming by cell fusion can be considered as underlying cellular processes in these chimeras.     

Chemical and Structural Analysis of Fibre and Core Tissues from Flax

Samples of flax ( Linum usitatissimum ) stems from the cultivars ‘Natasja’ and ‘Ariane’ were separated into fibre and core fractions and analysed by gas–liquid chromatographic methods, ¹³C CPMAS NMR spectrometry, histochemistry, electron microscopy and UV absorption microspectrophotometry to assist in determining the structure and composition of these cell walls in relation to quality and utilisation. Analyses from chromatography and NMR gave similar results for carbohydrate and phenolic constituents in various samples and in the lower, more mature regions of the stem. Amounts of uronic acids and xylose were lower while amounts of mannose, galactose and glucose were higher in fibre vs core fractions. Quantities of phenolic constituents were significantly higher in the core than the fibre, with groups representative of both guaiacyl and syringyl lignins; amounts of phenolic acids were low. NMR showed a low intensity signal for aromatics in fibre, and it is possible that such signals arise from compounds in the cuticle rather than the fibre. Microscopic studies indicated that aromatic constituents were present in core cell walls, cuticle of the epidermis, and cell corners and middle lamellae of some regions within the fibre tissues. The lignin in fibre appeared to be of the guaiacyl type and may be too low in concentration to be unambiguously detected by NMR. Aromatic compounds were not observed in the epidermis or parenchyma cell walls. Similar analyses of dew-retted (unscutched) samples indicated that core tissues were mostly unchanged from unretted samples. Retted fibre tissues still contained lignified cell corners and middle lamellae in some regions. The cuticle, which was associated with retted fibres, was not degraded by dew-retting fungi. Fungi removed interfibre materials in some places and at times degraded the secondary wall near the cell lumen of fibre cells. Results indicate that microspectrophotometry and histochemistry are useful to identify the location and type of aromatics in fibre cell walls.     

Correlation between Pod Shape Traits and Its Fiber Quality of Wild Calotropis Gigantea

Seed fiber in the Calotropis gigantea (C. gigantea) pods is the most valuable component and can be developed into textile material. Cultivating high-yield and high-quality seed fibers for C. gigantea is one of the critical preconditions for its textile industrialization. In this paper, pods picked from wild C. gigantea plants were used as the experimental materials. The fiber length distribution of the pods was studied. The pod characters (pod shape, single pod weight, fiber weight per pod and seed number per pod, etc.) and the crucial quality characteristics of seed fibers (length, diameter and strength) were tested. The correlations between them were analyzed. The results show that the fiber lengths at the tip, the petiole and the middle part of the pods are significantly different: the fibers from the two sides of the middle part are the longest and more uniform. The pod shape is closely correlated with the fiber length, fineness and strength: longer pods have longer fiber length, smaller length variation and larger fiber diameter, and the percentage of low strength fiber (single fiber strength <1.2 cN) is significantly lower compared to smaller pods. Cultivating C. gigantea with large size and heavy pods will improve the seed fiber yield and the fiber quality.