松油烯-4-醇对粘虫幼虫体壁结构的影响

用砂地柏精油主要杀虫活性成分松油烯 - 4 -醇熏蒸处理粘虫 6龄中期幼虫后 ,在扫描电镜下观察了不同中毒阶段粘虫体表蜡质颗粒及体壁底膜的变化。结果表明 ,松油烯 - 4 -醇处理可导致粘虫幼虫体表蜡质层颗粒形态和排列形式发生改变 ,颗粒间空隙变大 ,体壁底膜也有一定程度的破坏 ,这些病变可能是导致体表失水的主要原因。     

黄瓜PGPR菌株根部定殖的扫描电镜研究

扫描电镜观察植物根际促生细菌(PGPR)菌株在限菌状况下黄瓜根部的定殖，结果显示根部定殖具宏观不均匀性，只在根面的少部分能够定殖，即存在有利于PGPR生长繁殖的生态位点；供试PGPR菌株在根部的扩展方式主要有2种：由根尖的被动携带和随根表水膜转移。     

百合种质资源花粉形态及亲缘关系研究

利用扫描电镜对12个分布于我国的百合Lilium种(包括2个变种)及6个栽培品种进行花粉形态观察与比较研究。结果表明,百合属花粉粒为椭圆体至长椭圆体,萌发沟均为单萌发沟,萌发沟长达两端。表面纹饰网纹,网眼为不规则多边形至近圆形,大小不一。网脊由瘤状或盘珠状颗粒较紧密排列而成,单排基柱,脊宽1.17~2.48μm,有时有断点。网眼内有疣状、瘤状或棒状突起,少数品种无突起。在花粉形态性状比较基础上,初步探讨了百合属植物的系统进化关系。通过对供试18个种、变种及品种的5个花粉形态指标进行聚类分析,结果除卷丹L. lancifolium外,较准确地将形态分类上的百合组与卷瓣组聚为2个类群。图2表2参13     

Effect of pre-cooking in potato granule production by a freeze-thaw process

Summary Steam-cooked potatoes pre-cooked for 20 min at 70 C were firmer than those cooked without pre-treatment. The product remained intact and required a greater force for subdivision into smaller aggregates. Excessive cell damage was sustained during the mashing step of the freeze-thaw (F-T) process, resulting in a gluey mash which could not be easily processed into granules. The pectic substances of the potatoes with pre-treatment were less solubilized than those cooked without. This suggested that they were made more resistant to thermal degradation by pre-cooking, resulting in greater intercellular cohesion and less rarefaction of the cell wall during subsequent cooking. Cell separation was poor in the following F-T process. Electron photomicrographs showed that precooking gelatinized the starch and that the cell wall remained unseparated.

---

Zusammenfassung Ged?mpfte Kartoffeln, 20 Minuten bei 70±1 C vorbehandelt, wiesen eine festere Konsistenz auf als solche ohne Vorbehandlung (Tab. 2). Dieses Produkt blieb eher intakt und es erforderte mehr mechanische Arbeit, um es in kleinere Bruchstücke zu zerteilen, die eine Vorbedingung des Gefrier-Tau-Verfahrens (G-T-Verfahren) sind. Dies verursachte gr?ssere Sch?den, die zur Bildung eines klebrigen Breis führten (Tab. 3), der mit dem G-T-Verfahren nicht zu Granulat verarbeitet werden konnte. Trotz einiger ?nderungen des Verfahrens, z.B. l?ngeres Pürieren und tiefere Trocknungstemperatur, war die Ausbeute an Granulat gering und die Anzahl der verletzten Zellen hoch (Tab. 1). So behandelte Kartoffeln zeigten eine geringere L?slichkeit pektinartiger Verbindungen (672.2 mg Galakturonide pro 100 g Trockenmasse) als ged?mpfte Kartoffeln ohne Vorbehandlung (1106 mg/100 g Trockenmasse). Das D?mpfen allein schien alle pektinartigen Substanzen in L?sung zu bringen, w?hrend ein Drittel des Pektins ungel?st blieb, wenn die Kartoffeln vorbehandelt wurden (Tab. 4). Dies l?sst vermuten, dass durch die Vorbehandlung die pektinartigen Substanzen gegen weitere Hitzeeinflüsse resistent werden, was zu einer Verminderung des Verlustes des interzellul?ren Zusammenhaltes sowie einem verminderten dünner werden beim darauffolgenden D?mpfen führt. Deshalb war das Kartoffelgewebe fester als dasjenige, welches nicht vorbehandelt wurde. Elektronenmikroskopische Untersuchungen zeigten, dass das Vorkochen die St?rke gelatinisierte und die Zelle lose füllte, w?hrend die meisten Zellw?nde aneinander haften blieben (Abb. 2 und 3). Da die Bindungskr?fte zwischen den Zellen sogar nach dem D?mpfen gut erhalten blieben, war die Zellabspaltung im darauffolgenden G-T-Verfahren gering (Abb. 8–11).

---

Résumé Les pommes de terre cuites à la vapeur après avoir subit une précuisson pendant 20 min à 70±I C sont plus fermes que celles obtenues sans précuisson (tableau 2). Un tel produit a tendance a rester intact et demande une plus grande action mécanique pour être reduit en particules plus petites lors de la mise en purée par la méthode requise lors du procédé ‘freezethaw’ (F-T). Ceci entraine des domages importants des cellules, rendant la purée collante et impropre à la granulation lors du procédé F.T. (tableau 3). Même par le biais de quelques modifications du procédé, e.g. un malaxage plus long de la purée et une température de séchage inférieure, le rendement en granules reste faible et le nombre de cellules broyées trés élevé (tableau 1). Les pommes de terre subissant ce traitement présentent une faible solubilisation des substances pectiques (673.2 mg d’uronide par 100 g de matière sèche) comparé aux pommes de terre cuites sans précuisson (1106 mg/100 g de matière sèche). La cuisson à la vapeur semble solubiliser à elle seule toutes les substances pectiques utilisables alors qu’un tiers de la pectine reste insolubilisée lorsque le produit a subit une précuisson (tableau 4). Ceci suggère que la précuisson rend les substances pectiques plus resistantes à toute dégradation thermique successive, diminuant la perte de liaisons entre les cellules et raréfiant la séparation des parois cellulaires lors de la cuisson. Donc, les tissus obtenus sont plus fermes que ceux qui n’ont pas re?u de prétraitement. Des photos au microscope électronique montrent que la précuisson gélatinise l’amidon qui remplit alors tout le volume cellulaire tandis que la plupart des parois cellulaires restent liées les unes aux autres (figures 2 et 3). Les forces de liaison entre cellules restant donc importantes même après cuisson à la vapeur, la séparation des cellules est mauvaise lors des étapes suivantes du procédé F-T (figures 8 à 11).

     

Surface properties and locations of gluten proteins and lipids revealed using confocal scanning laser microscopy in bread dough

Surface properties of gluten proteins were measured in a dilation test and in compression and expansion tests. The results showed that monomeric gliadin was highly surface active, but polymer glutenin had almost no surface activity. The locations of those proteins in bread dough were investigated using confocal scanning laser microscopy and compared with polar and nonpolar lipids. Added gluten proteins participated in the formation of the film or the matrix, surrounding and separating individual gas cells in bread dough. Gliadin was found in the bulk of dough and gas ‘cell walls’. Glutenin was found only in the bulk dough. Polar lipids were present in the protein matrix and in gas ‘cell walls’, as well as at the surface of some particles, which appeared to be starch granules. However, nonpolar lipid mainly occurred on the surface of particles, which may be starch granules and small lipid droplets. It is suggested that the locations of gluten proteins in bread dough depends on their surface properties. Polar lipid participates the formation of gluten protein matrix and gas ‘cell walls’. Nonpolar lipids may have an effect on the rheological properties by associating with starch granule surfaces and may form lipid droplets.     

Colonization of soft wheat following infection of the stem base by Fusarium culmorum and translocation of deoxynivalenol to the head

Following inoculation of the base of soft wheat seedlings with Fusarium culmorum, disease symptoms typical of crown rot developed at the stem base and extended up to the third node by plant maturity. Fungus was isolated from all tissues exhibiting symptoms but not from symptomless tissues. Histopathological analysis revealed that the fungus was present mainly in the parenchymatic cells of the stem base and colonized the tissues via apoplastic and symplastic pathways. Host response in advance of pathogen colonization was observed. At maturity, plants were divided into sections from the inoculated area to the head. Heads were also separated into grain, rachis and chaff components. Colonization by the fungus was assessed by isolation from surface‐sterilized segments and quantified by real‐time PCR. Disease symptoms and the fungus were detected up to the third node, while deoxynivalenol (DON) was present in all stem segments and heads. Within the head, the DON concentration was higher in the rachis than in the chaff and grain components. These results demonstrate that F. culmorum can extensively colonize stem tissues but not reach the head by the time of plant maturity. In contrast, DON was detected in tissues beyond those colonized by the fungus, translocating to the head where, although accumulating mainly in the rachis, significant quantities accumulated in the grain. These findings indicate that there is a potential threat of contamination of grain with DON where severe crown rot is present in a crop.     

Chemical composition and profile characterisation of pumpkin (Cucurbita maxima) seed oil

Seeds of a Tunisian variety (Béjaoui) of pumpkin (Cucurbita maxima) were analysed for their main chemical composition and for their oil properties. Expressed on dry weight basis, seed moisture was 8.46%, whereas contents of proteins, fibre, ash, fat, and total sugars established at 33.92%, 3.97%, 21.97%, 31.57%, and 0.11% respectively. Gas chromatography revealed that the major fatty acids were oleic, linoleic, and palmitic acids (44.11%, 34.77%, and 15.97% respectively). Seed oil was also found to be rich in tocopherols with a predominance of δ-tocopherol (42.27%). The sterol marker β-sisosterol accounted for 39.6% of total sterols contained in seed oil of this variety. Six phenolic acids (protocatechuic, caffeic, syringic, vanillic, p-coumaric and ferulic) were detected, the syringic acid being predominant (7.96 mg/100 g). As a whole, based on its seed oil features, pumpkin may be considered as a valuable source for new multi-purpose products for industrial, cosmetic, and pharmaceutical utilisation.     

基于CT技术的原状黄土细观结构动态演化特征

非饱和原状黄土具有典型的结构性,结构性对其强度、变形等特征产生重要影响,但结构性对其屈服特性的影响却鲜有报道。为研究结构性对非饱和原状黄土在各向等压加载过程中的屈服特征影响规律,以非饱和土多功能三轴仪为研究工具,对4个非饱和原状黄土试样进行控制吸力的各向等压加载试验。借助CT(computerized tomography)技术,对变形和排水稳定后黄土试样进行实时动态扫描,将加载过程中的宏观力学指标与细观扫描数据联系,以明晰原状黄土加载过程中的结构演化规律。结果表明:原状黄土屈服前,CT数ME增长缓慢,说明结构性起到了抵御外部荷载的作用;当试样屈服后,ME呈线性增长趋势,试样进入塑性硬化阶段,结构性的作用明显降低。吸力增大时,原状黄土结构性对其力学变形特征影响较小;而吸力减小时,土颗粒之间水膜润滑作用明显,结构性对于抵抗外部荷载的作用增强。施加净平均应力后的原状黄土,其内部的孔洞和孔隙会减小,但不会完全闭合,这与新形成的结构能抵御外部荷载有关。研究结果可为进一步建立原状黄土结构性本构模型提供借鉴。