魔芋球茎中的β-甘露聚糖酶

迄今研究高等植物的β-甘露聚糖酶主要是用贮藏甘露聚糖的种子为材料(Halmer等1975,Halmer和Bewley 1979,Reid等1977,McCleary 1983)。营养器官贮藏甘露聚糖的植物,仅存在于单子叶植物的少数科(Meier和Reid 1982)。魔芋球茎贮藏大量甘露聚糖,Sugiyama等(1973)和Shimahara等(1975)从萌发的球茎中部分纯化了β-甘露聚糖     

60Coγ射线辐照对花魔芋同工酶与品质的影响

本文开展了^60Coγ射线辐照对花魔芋酶类与球茎品质影响的研究。结果表明：辐照诱发了花魔芋同工酶谱的变异,经等电聚焦电泳分析,不同剂量处理,酯酶和多酚氧化酶同工酶酶带呈现多态性,有稳定带和可变带,带型和带数的变化从分子水平揭示了魔芋辐射敏感性,是诱变效应和农艺性状突变的分子基础;经采后球茎品质检测,辐照引起了魔芋品质变化,数据分析表明干物质含量、葡甘聚糖含量、葡甘聚糖粘度与辐照剂量均呈二次曲线关系,总生物碱含量与剂量呈线性负相关。以葡甘聚糖的量和质为评价依据,中等辐射剂量范围内的辐照处理可提高魔芋品质。     

槐种子发育中胚乳细胞半乳甘露聚糖积累的研究

槐 ( Sophora japonica L.)开花约 60 d至种子成熟 ,为胚乳半乳甘露聚糖积累期。用组织化学方法 ,对储藏于胚乳细胞壁上的半乳甘露聚糖的形成积累进行了观察 ,结果表明 ,半乳甘露聚糖最先在邻近胚的胚乳细胞的粗面内质网的囊泡腔内形成 ,并通过细胞质膜分泌至细胞壁周围。此后 ,半乳甘露聚糖的积累逐渐向种皮方向扩展 ,及至种子成熟时 ,除糊粉层外 ,所有胚乳细胞几乎全由多糖所填充。此外 ,对半乳甘露聚糖发生部位及其积累过程的消长变化进行了讨论     

60Coγ射线辐照对花魔芋农艺性状的影响

本试验开展了^60Coγ射线辐照对花魔芋(Amorphophallus konjac)农艺性状影响的研究。结果表明：辐射诱发了大量有利的或损伤的数量性状变异。这些可观察或可检测的变异有形态异常,主要表现为植株矮小及叶片畸形(包括叶片黄化、缺刻、叶卷曲及主叶脉粘连不分离等);还有其它的性状变化,如生长期、根系、鞭状茎分化、耐寒性,球茎增重和产量等。观察发现,辐射效应的主要特征是抑制和损伤,并有一定程度的生理修复。通过分析,这些数量性状的变化符合统计规律,如植株叶片面积的变化与辐射剂量关系可拟合成三次曲线,其它的性状变化与剂量成二次曲线。在花魔芋生长期间发现了大叶片植株、耐寒植株、少鞭状茎分化植株和高球茎增重系数植株等有益突变。大叶片可增加光合作用面积,提高产量;少鞭状茎分化可减少球茎物质分流,使积累更加有效;耐寒抗寒既可延长生长期,也可扩大种植范围和向适宜地区推广。通过实验,得出花魔芋的辐射敏感性强,诱变效应显著,性状变异有可选择性,辐射诱变育种和种质改良可行。此外,魔芋种植多采用无性繁殖方式,有些有利的变异性状可直接作为育种和引种驯化的基础材料利用。     

诺卡氏菌形放线菌β-甘露聚糖酶的水解特性

诺卡氏菌形放线菌（Nocardioform actinomycetes）NA3-540产生的β-甘露聚糖酶（ManNA）能不同程度地水解槐豆胶、瓜胶、田菁胶和魔芋胶等甘露多聚糖为组分的植物胶,生成系列甘露寡糖;该酶只轻微地水解香豆胶,不能水解β-甘露聚糖、黄原胶、海藻胶;ManNA对槐豆胶、瓜胶和魔芋胶多糖的Km值和Vmax分别为1．75、6．13、3．9mg／mL和2485、1303、853μmol／（min／mg）,表明槐豆胶是该酶的理想水解底物。ManNA水解几种植物胶的明显差异,表明甘露聚糖的糖链组成和空间结构明显地影响着β-甘露聚糖酶的水解活性。     

小麦籽粒发育及淀粉晶体特性对花后高温胁迫的响应

选用2个品质类型和成熟期不同的新疆主栽小麦品种‘新春11号’和‘新春39号’,分别进行花后灌浆早期高温(花后5~8d,32℃,T_1)和中期高温(花后15~18d,38℃,T_2)处理,分析花后高温对小麦籽粒发育及淀粉晶体的影响。结果显示:(1)T_1处理明显降低了两品种籽粒长度和粒重,而T_2处理显著影响籽粒宽度和厚度;高温处理虽然降低了籽粒灌浆速率,但两品种灌浆最大峰值出现时间均在花后18d。(2)T_1处理对小麦籽粒A型淀粉粒形态的影响较大,中熟品种‘新春11号’的A型淀粉粒表面在花后10d时可观察到微孔,在花后15~20d时其粒径明显小于同期对照,在花后20~25d时淀粉粒表面压痕增多且A、B型淀粉粒表面出现明显缢缩;而早熟品种‘新春39号’淀粉粒形态和粒径大小受花后高温的影响相对较小。(3)两品种在不同高温处理下,其淀粉粒晶体特性衍射峰出现的位置相同,但淀粉粒的尖峰强度不同,表明高温胁迫不影响淀粉粒的晶体类型,但可能改变了淀粉粒内部的层状结构。研究表明,花后早期高温不仅对小麦籽粒外部形态有较大的影响,同时也影响到籽粒内部淀粉粒的形态和晶体的特性。     

魔芋的经济开发评价

魔芋是一种经济价值和医疗保健价值极高的多年生草本植物。明李时珍在本草纲目中记载,“魔芋主治痛肿风毒,摩傅肿上。捣碎,以汁煮成饼,五味调食,(状如水母丝)主消渴”。中医讲的消渴即现代医学的糖尿病。现代科学业已查明,魔芋含有一种许多植物都没有的特殊成份——葡萄甘露聚糖,其干粉中含量可达58％     

魔芋甘露聚糖化学结构的研究

研究了陕西花魔芋块茎中分离所得的魔芋甘露聚糖的化学结构与分子组成。经葡聚糖凝胶Ｇ－７５柱层析为一组均一性多糖,气相色谱检测由甘露糖,葡萄糖组成,其克分子比Ｍａｎ;Ｇｌｕ＝１．７８：１,平均分子量为１１×１０＾－５。     

甘露聚糖结合蛋白基因突变引起的免疫缺陷

甘露聚糖结合蛋白基因突变引起的免疫缺陷陈政良（第一军医大学免疫学教研室,广州５１０５１５）关键词甘露聚糖结合蛋白基因突变免疫缺陷甘露聚糖结合蛋白（ＭＢＰ）是一种血清Ｃ型凝集素。其肽链包括Ｎ末端区、含Ｇｌｙ－Ｘ－Ｙ重复顺序的胶原样区（ｃｏｌａｇｅｎ－ｌ...     

中国薯蓣属植物地下茎淀粉粒形态特征及其分类学意义

对中国薯蓣属（Dioscorea L．）40个种类地下茎的淀粉粒形态进行了显微观察。结果表明,中国薯蓣属植物地下茎淀粉粒主要有单粒和复粒2种形态。单粒淀粉粒以类圆形为主,脐点多为点状。复粒淀粉粒可分为2类：A型由2～3个淀粉小粒构成,以卵圆形和三角形为主,脐点点状且大多不明显,少数种类层纹清晰;B型由10个以上的淀粉小粒构成,以圆形为主,脐点不明显,无层纹。根状茎组（Sect．Stenophora Uline）、基生翅组（Sect．Opsophyton Uline）和周生翅组（Sect．Enantiophyllum Uline）均为单粒淀粉粒;顶生翅组（Sect．Shannicorea Prain et Burkill）为复粒淀粉粒A型;丁字型毛组（Sect．Combilium Pra Jnet Burkill）和白薯莨组（Sect．Lasiophyton Uline）为复粒淀粉粒B型;复叶组[Sect．Botryosicyos（Hochst．）Uline]兼有单粒和复粒淀粉粒。淀粉粒形态特征支持白薯蓣（D．hispida Dennst．）由复叶组分出单列成组及毛芋头薯蓣（D．kamoonensis Kunth）和高山薯蓣（D．delavayi Franch．）互为独立种的分类学处理。     

Histochemical Localization of Calcium Oxalate Crystals in Starch Grains of Yams (Dioscorea)

The bulbils and/or tubers of seven species of yams (Dioscorea)were examined for crystal content using light microscopy andhistochemistry. Calcium oxalate crystals in the form of raphide bundles werelocalized in the parenchymatous tissues. Within starch grains,crystals of various shapes and sizes were observed. The variationin shape and sizes of the intra-amylar crystals could be exploitedfor taxonomic purposes. Calcium oxalate crystals appear to serve a storage functionin these starch grains. Yams, Dioscorea, raphides, oxalate crystals, histochemistry     

In situ Imaging of Pea Starch in Seeds

A method has been developed for the in situ imaging of starch in dry seeds by exploiting the tight packing of the starch and protein storage reserves within the cells of the embryo. The method can be adapted to prepare seed samples which are suitable for light microscopy (birefringence and iodine staining), scanning electron microscopy and atomic force microscopy. Its potential for imaging the internal structure of starch granules without any prior isolation process is demonstrated for round smooth peas. Using a standard ultramicrotome, thin sections were cut directly from selected regions of dry pea seeds and examined by light microscopy before and after hydration. The sectioning procedure left a planed surface with the internal structure of the starch granules exposed. This material was examined by scanning electron microscopy and atomic force microscopy directly or after controlled hydration. In the hydrated pea samples, the growth ring structure and blocklet sub-structure of individual starch granules within the seed were visualised directly by atomic force microscopy. Furthermore, the effects of hydration and staining were monitored and have been used to introduce contrast into the images. The observations have revealed new information on the blocklet distribution within pea starch granules and the physical origins of the growth ring structure of the granules: the blocklet distribution suggests that the granules contain alternating bands with different levels of crystallinity, rather than alternating amorphous and crystalline growth rings.     

Composition of Soluble Nucleotides in Growing Corms of Amorphophallus konjac C. Koch

The nucleotides and the activities of both sucrose synthetase and granular starch synthetase in the konjak corm (Amorphophallus konjac C. Koch) have been investigated as a preliminary experiment on konjak mannan biosynthesis. On chromatographic separation on anion exchange resin and paper of compounds present in the acid ethanol extract from the corms, ascorbic acid, AMP, ADP, ATP, ADP-glucose, UTP, UDP-glucose, GTP, and GDP-mannose were isolated and tentatively identified. An unidentified nucleotide was also isolated.

Of the three nucleotide sugars, UDP-glucose was the most plentiful, while ADP-glucose was the least. The sucrose synthetase in konjak corms was as active as that in other plants. These observations suggest that the mechanism involved in sucrose cleavage in konjak corms is the same as that in other plants, such as sweet potato roots. Starch synthetase bound to starch granules in konjak corms was also found to be active when ADP-glucose was used as glucose donor. But UDP-glucose could not be substituted for ADP-glucose.

Based on these observations the mechanism of konjak mannan biosynthesis is discussed.     

The Role of Druse and Raphide Calcium Oxalate Crystals in Tissue Calcium Regulation in Pistia stratiotes Leaves

Abstract: Ca oxalate crystal formation was examined in Pistia stratiotes L. leaves during excess Ca and Ca-deficient conditions. Pistia produces druse crystal idioblasts in the adaxial mesophyll and raphide idioblasts in the abaxial aerenchyma. Raphide crystals were previously found to grow bidirectionally, and here we show that Ca is incorporated along the entire surfaces of developing druse crystals, which are coated with membrane-bound microprojections. Leaves formed on plants grown on 0 Ca medium have fewer and smaller druse crystals than leaves formed under 5 mM Ca ("control") conditions, while raphide crystal formation is completely inhibited. When plants were moved from 0 to 15 mM ("high") Ca, the size and number of crystals in new leaves returned to (druse) or exceeded (raphide) control levels. High Ca also induced formation of druse, but not raphide, crystals in differentiating chlorenchyma cells. When plants were transferred from 15 mM Ca to 0 Ca, young druse crystals were preferentially partially dissolved. Oxalate oxidase, an enzyme that degrades oxalate, increased during Ca deficiency and was localized to the crystal surfaces. The more dynamic nature of druse crystals is not due to hydration form as both crystal types are shown to be monohydrate. Part of the difference may be because raphide idioblasts have developmental constraints that interfere with a more flexible response to changing Ca. These studies demonstrate that excess Ca can be stored as Ca oxalate, the Ca can be remobilized under certain conditions, and different forms of Ca oxalate have different roles in bulk Ca regulation.     

Heterogeneity of lotus rhizome starch granules as revealed by α-amylase degradation

Lotus (Nelumbo nucifera Gaertn.) rhizome starch granules have an elongated oval shape with the hilum located at one end. The morphologic characteristics were used as a direction anchor to study the heterogeneity of molecular organization of starch granules using microscopy before and after partial digestion by bacterial α-amylase (Bacillus sp.) The partially digested granule showed a single, big eroded hole at the end distant from the hilum. The enzyme-attacked end was revealed to be the loosely packed end and to be the weak point for enzyme hydrolysis. The α-amylase hydrolyzed the loosely packed central part of the granule faster than the densely packed periphery, and left an empty shell with a fish-bone-like tunnel inside. The periphery was more resistant to amylase hydrolysis and had strong birefringence. For the whole starch granule, the selectivity of α-amylase hydrolysis was low for the crystalline and amorphous regions and for amylose and amylopectin molecules. This study elucidated that the molecular organization of lotus rhizome starch granules was heterogeneous.     

The molecular deposition of transgenically modified starch in the starch granule as imaged by functional microscopy

The molecular deposition of starch extracted from normal plants and transgenically modified potato lines was investigated using a combination of light microscopy, environmental scanning electron microscopy (ESEM) and confocal laser scanning microscopy (CLSM). ESEM permitted the detailed (10 nm) topographical analysis of starch granules in their hydrated state. CLSM could reveal internal molar deposition patterns of starch molecules. This was achieved by equimolar labelling of each starch molecule using the aminofluorophore 8-amino-1,3,6-pyrenetrisulfonic acid (APTS). Starch extracted from tubers with low amylose contents (suppressed granule bound starch synthase, GBSS) showed very little APTS fluorescence and starch granules with low molecular weight amylopectin and/or high amylose contents showed high fluorescence. Growth ring structures were sharper in granules with normal or high amylose contents. High amylose granules showed a relatively even distribution in fluorescence while normal and low amylose granules had an intense fluorescence in the hilum indicating a high concentration of amylose in the centre of the granule. Antisense of the starch phosphorylating enzyme (GWD) resulted in low molecular weight amylopectin and small fissures in the granules. Starch granules with suppressed starch branching enzyme (SBE) had severe cracks and rough surfaces. Relationships between starch molecular structure, nano-scale crystalline arrangements and topographical-morphological features were estimated and discussed.     

Structure of Crystal Cells and Influences of Leaf Development on Crystal Cell Development and Vice Versa in Phaseolus vulgaris (Leguminosae)

The structure of cells with calcium oxalate crystals and their nelghbouring cells has been studied by light and transmission electron microscopy at different stages of bean leaf development. Plants were grown with varying calcium supply to identify a possible influence of calcium nutrition on cell structure. Crystals are formed inside the vacuole of already highly vacuolated cells of bundle sheath extensions. The membrane around the crystal vacuole is continuous with the plasmalemma. The crystal vacuole contains membraneous structures. In the fully expanded leaf the crystal becomes ensheathed by wall material. Chloroplasts of bundle sheath extension cells, with or without crystals, are smaller, with fewer membranes, and with much narrower stroma regions than those of the palisade parenchyma. There is a stage in the young leaf when only the bundle sheath extension cells without crystals have starch grains in their chloroplasts. As their number is lower in plants grown with high calcium supply this means that, in this case, less cells are competent for photosynthesis.     

Development of secretory cells and crystal cells in Eichhornia crassipes ramet shoot apex

The distribution and development of secretory cells and crystal cells in young shoot apexes of water hyacinth were investigated through morphological and cytological analysis. The density of secretory cells and crystal cells were high in parenchyma tissues around the vascular bundles of shoot apexes. Three developmental stages of the secretory cells can be distinguished under transmission electron microscopy. Firstly, a large number of electron-dense vesicles formed in the cytoplasm, then fused with the tonoplast and released into the vacuole in the form of electron-dense droplets. As these droplets fused together, a large mass of dark material completely filled the vacuole. To this end, a secretion storage vacuole (SSV) formed. Secondly, an active secretion stage accompanied with degradation of the large electron-dense masses through an ill-defined autophagic process at periphery and in the limited internal regions of the SSV. Finally, after most storage substances were withdrawn, the materials remaining in the spent SSV consisted of an electron-dense network structure. The distribution and development of crystal cells in shoot apical tissue of water hyacinth were also studied by light and electron microscopy. Crystals initially formed at one site in the vacuole, where tube-like membrane structures formed crystal chambers. The chamber enlarged as the crystal grew in bidirectional manner and formed needle-shaped raphides. Most of these crystals finally occurred as raphide bundles, and the others appeared as block-like rhombohedral crystals in the vacuole. These results suggest that the formation of both secretory cells and crystal cells are involved in the metamorphosis of vacuoles and a role for vacuoles in water hyacinth rapid growth and tolerance.     

Electron microscopy of hemosiderin; presence of ferritin and occurrence of crystalline lattices in hemosiderin deposits

Injections of hemoglobin were given to rats in order to produce hemosiderosis, and selected hemosiderin granules in sectioned cells of proximal convoluted tubules were studied by means of electron microscopy. When examined at high resolution, many of the dense particles that were present in hemosiderin granules proved to have the structure that characterizes the iron hydroxide micelles of molecular ferritin. In some hemosiderin deposits the dense particles formed lattices similar to those present in sections of crystalline ferritin. Such ordered arrangement of dense particles was encountered inside as well as outside of the cytoplasmic organelles for which the name "siderosomes" has been proposed previously, and which may be derived from mitochondria. Study of hemosiderin granules in hepatic parenchymal and reticuloendothelial cells of human beings yielded similar results. The findings confirm the inference that ferritin is a component of hemosiderin, and they indicate that some of the so called hemosiderin granules are crystals of ferritin.     

Electron Microscopy of Hemosiderin: Presence of Ferritin and Occurrence of Crystalline Lattices in Hemosiderin Deposits

Injections of hemoglobin were given to rats in order to produce hemosiderosis, and selected hemosiderin granules in sectioned cells of proximal convoluted tubules were studied by means of electron microscopy. When examined at high resolution, many of the dense particles that were present in hemosiderin granules proved to have the structure that characterizes the iron hydroxide micelles of molecular ferritin. In some hemosiderin deposits the dense particles formed lattices similar to those present in sections of crystalline ferritin. Such ordered arrangement of dense particles was encountered inside as well as outside of the cytoplasmic organelles for which the name "siderosomes" has been proposed previously, and which may be derived from mitochondria. Study of hemosiderin granules in hepatic parenchymal and reticuloendothelial cells of human beings yielded similar results. The findings confirm the inference that ferritin is a component of hemosiderin, and they indicate that some of the so called hemosiderin granules are crystals of ferritin.