大豆根瘤侵染细胞中一种细胞质内含物的电镜观察

在中国丰收11号大豆根瘤侵染细胞中,我们发现了一种电子密度很高,体积很大,形状为圆形或近似圆形,外面没有界膜,常位于胞间隙附近的特殊的细胞质内含物。高尔基体及其小泡,丰富的粗糙型内质网和核糖体常在它的附近,其中一些核糖体正沉积在它的表面。它主要是由核糖体凝聚而成,高尔基体和内质网在它的形成中也起了一定作用。它的内部含有颗粒状,纤维状,泡状和管状物质。它的出现似乎与侵染细胞固氮有关。     

箭舌豌豆根瘤液泡中细菌周膜来源的研究

电镜观察结果表明,幼龄箭舌豌豆根瘤侵染细胞的细胞质较少,中央是一些体积较大的液泡。细胞质中侵入线经常可见,由侵入线释放出来的细菌均有细菌周膜。这些细菌只位于细胞质中,不出现在液泡里面。成熟根瘤中的侵染细胞与此不同,它们中有大量的成熟侵染细胞,细胞质丰富,里面充满大量细菌,中央常有一个大液泡。当中央液泡发育到一定程度时,位于其附近的细菌可通过液泡膜内吞、液泡膜与细菌周膜融合及液泡膜破裂3种途径进入液泡,后一种途径常伴有寄主细胞质。液泡中的细菌绝大部分裸露在外,只有个别细菌具有细菌周膜且多位于液泡膜的破损处附近,因此细菌周膜可能是原来就有的。     

豆科根瘤非侵染细胞的形态结构研究

非侵染细胞是豆科根瘤中一种非常重要的细胞,它不仅参与了根瘤共生固氮,而且还在其中起了极为重要的作用,这些作用的发挥与其具有与此相适应的形态结构和分布有关。非侵染细胞体积小、数量少,分散于侵染细胞之间。在大豆根瘤中,它们彼此相连接,形成一条条的线和一个个的面,由根瘤中心向四周辐射,直至与皮层细胞相接,其作用可能与根瘤中心组织和皮层细胞之间的物质运输,特别是固氮产物的输出密切有关。非侵染细胞与侵染细胞之间的主要差异在于它不含细菌,中央有一个大液泡,细胞质中含有大量的过氧化物酶体和许多膨大的管状内质网,而且细胞壁上还有丰富的胞间连丝和纹孔,但主要存在于非侵染细胞与非侵染细胞之间的连接壁上。     

豌豆根瘤细菌周膜在发育中的变化

细菌周膜随发育不同而异。侵入线中的细菌没有细菌周膜,刚从侵入线释放到寄主细胞质中的细菌虽有这一特殊结构,但一般较小,表面光滑。然后随着发育而不断变大,有的表面甚至出现凹凸不平。在这些细菌周膜附近,常有一些高尔基体和内质网,有的还有一些纤维状物质和泡状结构位于它所包围的电子透明区域中。当细菌周膜继续向外扩展时,常与相邻细菌周膜相互嵌合,进而彼此融合。这种融合是一种不对称性融合,只出现在即将或已成熟的被侵染的细胞中。细菌周膜融合可能与共生体系的固氮和物质交换有关。     

红豆草根瘤侵染细胞中液泡内含物的超微结构特征

用透射电镜研究了红豆草（Onobrychis viciifolia）根瘤侵染细胞中液泡内含物的超微结构特征。结果表明,早期发育侵染细胞的液泡中只含有少量的纤维状物质。随着细胞的发育,液泡不断变大,液泡中的纤维状物质和膜状物质越来越多。在中央液泡形成后,液泡中的纤维状物质逐渐减少,类细胞质、泡状和膜状物质明显增多,它们常由一层来自液泡膜的膜包围,其形状一般近似圆形或椭圆形。液泡内含物的大量出现可能与红豆草及其根瘤具有高度的抗旱件有关。     

几种罗汉松属植物根瘤的形态与结构

对分布在广西的几种罗汉松属植物自然结瘤的根瘤形态和显微结构进行了观察。结果表明:几种罗汉松属植物所结的根瘤形态是一致的,均为球形或近球形,直径约1.0～1.5mm。根瘤的组织结构从内向外包括:维管组织、薄壁细胞、侵染细胞和表皮(周皮);侵染细胞与薄壁细胞呈不均匀的相间分布。侵染细胞中所含菌体为细菌。此外还发现细叶罗汉松根瘤的侵染细胞中有变形膨大的细胞核。总体上看,罗汉松属植物根瘤在形态与结构上与豆科植物的根瘤有许多相似之处。     

豌豆根瘤的超微结构研究

用透射电镜详细地研究了中国张家川豌豆(Pisum sativum L.)根瘤的超微结构。结果表明,它在发育过程中经历了一系列的超微结构变化,这些变化包括侵染丝中细菌的释放,核仁联合体的出现,细菌侵染后寄主细胞核和细胞质的变化,细菌泡囊的融合,非侵染细胞的细微结构等。本文详细地描述了上述变化,讨论了这些变化的意义与豌豆根瘤发育的关系。     

Effects of phylloxera infestation on the root ultrastructure of grape cultivars with different resistance

[目的]探讨不同抗性葡萄品种对葡萄根瘤蚜Daktulosphaira vitifolia Fitch侵染后的组织结构响应.[方法]以砧木140Ru(Vitis rupestris×V.berlandieri)和栽培品种赤霞珠Vitis vinifera cv.Cabernet Sauvignon离体三级根及140Ru盆栽苗为试材接种根瘤蚜卵,接种两周后取刺吸位点组织作超薄切片并观察超微结构变化,取盆栽140Ru不同时期根结测定多酚含量.[结果]超微结构显示,砧木140Ru根系周皮层最外层细胞壁的厚度(1 031.25 nm)及周皮层细胞层数(6～7层)显著高于赤霞珠品种的周皮层细胞厚度(543.75 nm)及层数(3～4层),140Ru根系韧皮部酚类物质含量比赤霞珠高出35％;侵染后,砧木140Ru周皮层细胞第3层以内的细胞壁加厚并积聚大量的多酚类物质,140Ru葡萄新根被根瘤蚜侵染后多酚含量呈升高趋势,在接种20d时是对照的2.4倍;赤霞珠粗根被根瘤蚜侵染后薄壁细胞中细胞质变浓,出现大量淀粉粒,线粒体及内质网数量增多.[结论]砧木140Ru的周皮层组织结构较赤霞珠不利于根瘤蚜口针穿刺,被根瘤蚜侵染后发生了不利于根瘤蚜侵染取食的变化.     

大豆根瘤中公共细菌周膜形成的一种特殊方式

用透射电镜观察了大豆根瘤中公共细菌周膜的形成。在细菌周膜发育中,它的表面常常形成一些凸起和凹陷．而且相互嵌合,不过常为双嵌合。由干嵌合细菌周膜发生融合,因而在两个相邻细菌电子透明区之间形成两个狭窄的通道,通道之间一些含有丰富核糖体的寄主细胞质,但不含细胞器。随着融合面积的不断扩大．这些细胞质变得越来越少,最后完全消失。于是两个彼此独立的细菌周膜就完全变为一个公共的细菌周膜。融合后的细菌周膜还可继续融合,但融合机率则随着融合次数的增加变得越来越小。     

豌豆根瘤脂质体的分布及形态特征

豌豆根瘤中有大量的脂质体,广泛分布于非侵染细胞和侵染细胞内,它既可以存在细胞质中,也可位于液泡里面。有时单个存在,有时又多个聚集在一起。非侵染细胞与侵染细胞相比,前者中的脂质体明显多于后者。这些脂质体近似圆形或椭圆形,表面无膜,电子密度较高,内部无固定的结构,常有一些细胞器位于它的附近。讨论了脂质体的细胞发育及细胞种类的关系。     

Extent of high-affinity iron transport systems in field isolates of rhizobia

A Uruguayan rhizobia collection (67 isolates) obtained from nodules of Medicago sativa, Melilotus albus, Medicago polymorpha, Trifolium subterraneum, Trifolium repens, Trifolium vesiculosum, Lotus corniculatus, Lotus subbiflorus, Lotus pedunculatus, Ornithopus sp. and Adesmia sp. has been examined to assess the occurrence of high affinity iron uptake systems. CAS (Chrome-azurol S)-assay results suggested that most of the free-living form of these microsymbionts may produce siderophores. The highest siderophore production was observed among Medicago and Trifolium microsymbionts whereas no siderophore expression or moderate positive results were found among Lotus microsymbionts; suggesting that microsymbionts of legumes growing on neutral or alkaline soils may express in vitro enhanced siderophore production. Electrophoretic patterns of outer-membrane protein enriched fractions revealed that iron-limited microsymbionts of Medicago sativa, Lotus corniculatus, Lotus subbiflorus, Trifolium repens, Trifolium subterraneum and Ornithopus sp. produced high molecular weight proteins (ranging from 64 to 94 kDa) compared to cells grown in iron-sufficient media.     

Transfer of Rhizobium meliloti pSym genes into Agrobacterium tumefaciens: host-specific nodulation by atypical infection

The pSym megaplasmid of Rhizobium meliloti 2011 mobilized by plasmid RP4, or plasmid pGMI42, an RP4-prime derivative which carries a 290-kilobase pSym fragment including nitrogenase and nod genes, was introduced into Agrobacterium tumefaciens. The resulting transconjugants induced root deformations specifically on the homologous hosts Medicago sativa and Melilotus alba and not on the heterologous hosts Trifolium pratense and Trifolium repens. The root deformations were shown to be genuine nodules by physiological and cytological studies. Thus, host specificity nodulation genes are located on the pSym megaplasmid. Host nodulation specificity did not seem to require recognition at the root hair level since no infection threads could be detected in the root hairs. Cytological observations indicated that bacteria penetrated only the superficial layers of the host root tissue by an atypical infection process. The submeristematic zone and the central tissue of the nodules were bacteria free. Thus, nodule organogenesis was probably triggered from a distance by the bacteria. Agrobacterium transconjugants carrying pSym induced the formation of more numerous and larger nodules than those carrying the RP4-prime plasmid pGMI42, suggesting that some genes influencing nodule organogenesis are located in a pSym region(s) outside that which has been cloned into pGMI42.     

拟菌体包囊膜的动态变化和宿主细胞与细菌的相互关系

本文初次报道紫云英根瘤的超微结构。用根瘤中段的中心组织作实验材料,以显示受根瘤菌侵染的宿主细胞的一般结构。细菌借助于侵入线进入宿主细胞,发育成拟菌体,为包囊膜所裹。一个包囊膜内一般只有一个拟菌体。包囊膜可以与细胞质内的囊泡和小液泡融合而扩增,导致膜对拟菌体的包裹由紧密到疏松的变化。包囊膜和拟菌体表面都有突起,两者的突起相对接触和融合。对拟菌体包囊膜的动态变化与衰老的关系以及宿主细胞和拟菌体之间物质交换的关系进行了讨论。作者指出包囊膜的扩增和电子透明区域的存在,是拟菌体发育成熟的一个阶段,包囊膜和拟菌体通过互相突起、融合沟通的结构,可能是宿主细胞和细菌之间物质交换功能的一种表现。     

Oxygen-Induced Membrane Depolarizations in Legume Root Nodules (Possible Evidence for an Osmoelectrical Mechanism Controlling Nodule Gas Permeability)

Various stresses trigger rapid and reversible decreases in the O2 permeability (PO) of legume root nodules. Several possible mechanisms have been proposed, but no supporting data have previously been presented that meet the requirements for both rapidity and reversibility. Stomatal regulation of gas permeability in leaves involves electrically driven fluxes of inorganic osmoticants, so we investigated the possibility of a somewhat similar mechanism in nodules. We used microelectrodes to monitor membrane potential in intact, attached nodules of Glycine max, Medicago sativa, Lotus corniculatus, and Trifolium repens while controlling external O2 concentration and, in the case of G. max, measuring PO with a nodule oximeter. A 1- to 2-min exposure to 100 kPa O2 was found to induce rapid and reversible membrane depolarizations in nodules of each species. This depolarization (which, to our knowledge, is unique to nodules) is accompanied by reversible decreases in PO in G. max nodules. An osmoelectrical mechanism for control of nodule gas permeability, consistent with these data, is presented.     

游憩活动对琅琊山风景区两种草地植物种子发芽率的影响

在琅琊山风景区通过实地实验,分析了游憩活动对琅琊山风景区两种草地植物紫花苜蓿(Medicago sativa L.)和白三叶(Trifolium repens L.)种子发芽率的影响.结果表明:(1)游憩活动强度与两种植物种子发芽率呈负线性相关.近游道、中距离游道和远距离游道的3个实验组,紫花苜蓿种子平均发芽率依次为31.29%、39.41%、55.21%;白三叶依次为8.42%、14.62%、23.89%.距游道越远的实验组种子的发芽率越高,距游道最远的实验组和最近的实验组的种子发芽率差异显著.(2)柏油、水泥、台阶和泥质4种游道实验区的种子平均发芽率,紫花苜蓿依次为37.20%、40.27%、41.28%、48.13%;白三叶依次为10.37%、10.92%、14.23%、27.05%.旅游和游憩活动量较少的游道实验区种子的发芽率高于游憩活动量较大的游道实验区.此外,相同游道、相同实验位置的两种植物种子发芽率亦存在显著差异,表明不同植物种子萌发受到旅游活动的干扰存在差异.     

Monoclonal antibodies to antigens in the peribacteroid membrane from Rhizobium-induced root nodules of pea cross-react with plasma membranes and Golgi bodies

Three rat hybridoma lines that produced monoclonal antibodies reacting with the peribacteroid membrane from Pisum sativum were isolated, and these all appeared to recognize the same antigenic structure. Using one of these monoclonal antibodies, AFRC MAC 64, electron microscopy of immunogold-stained thin sections of nodule tissue revealed that the antigen, present in the peribacteroid membrane, was also found in the plant plasma membranes and in the Golgi bodies, but not in the endoplasmic reticulum. When peribacteroid membrane proteins were separated by SDS-polyacrylamide gel electrophoresis and transferred to nitrocellulose by electro-blotting, it was found that MAC 64 bound to a series of protease-sensitive bands that migrated in the mol. wt. range 50-85 K. The epitope was sensitive to periodate oxidation and its structure may therefore involve the carbohydrate component of a membrane glycoprotein. We suggest that this structure originates in the Golgi apparatus and is subsequently transferred to the peribacteroid membranes and plasma membranes. The monoclonal antibody also reacted with peribacteroid membranes from nodules of Vicia and lupin, and with plasma membranes and Golgi membranes from uninfected plant cells, including root tip cells from onion (Allium cepa), indicating that the antigen is highly conserved in the plasma membranes of plant cells.     

The host plant range of the pea aphid subspecies Acyrthosiphon pisum ssp. destructor (Johnson) (Hom., Aphididae)

Abstract:  In order to establish the host range of the pea aphid subspecies, Acyrthosiphon pisum ssp. destructor , and hence from which plant species pea crops are likely to become infested, the performance of this aphid on different leguminous plants was assessed. The plant species used were: Lotus uliginosus , Medicago sativa , Melilotus officinalis , Ononis repens , Sarothamnus scoparius , Trifolium hybridum , Trifolium pratense , Trifolium repens , Vicia cracca and Vicia faba . Vicia faba and Trifolium hybridum were the plants on which aphids reached the greatest size, took the least time to reach maturity, and experienced the lowest mortality. The time taken for the aphids to develop to maturity was negatively correlated with adult size, whereas survival to maturity was positively correlated with adult size. The host preference of the aphids was also assessed. The plant species selected as hosts by alatae were those on which their offspring performed best.     

油菜花蜜腺发育过程的超微结构变化与泌蜜机理的研究

油菜花蜜腺由２枚侧蜜腺和２枝中蜜腺组成,其基本结构类似。在蜜腺发育过程中,产蜜组织细胞内的内质网、高尔基体、质体和线粒体以及液泡都发生有规律变化。泌蜜前,细胞器的数量增加。其中,质体内积累淀粉,此过程与蜜腺内初皮部的分化并和线粒体的增加相关。泌蜜时,内质网数量增多,并产生小泡．小泡向质膜移动。泌蜜后,细胞液泡化,细胞器数量减少,细胞萎缩。根据观察结果分析,其原蜜汁来源于韧皮部,转运至产蜜组织细胞的质体、内质网和高尔基体内加工成蜜汁,最后通过胞吐和渗透相结合的方式泌出。     

Morphology of root nodules and nodule-like structures formed by Rhizobium and Agrobacterium strains containing a Rhizobium meliloti megaplasmid

We examined expression of the megaplasmid pRme41b of Rhizobium meliloti in two different Rhizobium sp. Strains and in Agrobacterium tumefaciens. Transfer of pRme41b into these bacteria was facilitated by insertion of a recombinant plasmid coding for mobilization functions of RP4 into the nif region (Kondorosi, A., E. Kondorosi, C.E. Pankhurst, W. J. Broughton, and Z. Banfalvi, 1982, Mol. Gen. Genet., 188:433-439). In all cases, transconjugants formed nodule-like structures on the roots of Medicago sativa. These structures were largely composed of meristematic cells but they were not invaded by bacteria. Bacteria were found only within infection threads in root hairs, and within intercellular spaces of the outermost cells of the structures. The donor strain of R. meliloti containing pAK11 or pAK12 in pRme41b initially produced nodules on M. sativa that did not fix nitrogen (Fix- ). In these nodules, bacteria were released from infection threads into the host cells but they did not multiply appreciably. Any bacteroids formed degenerated prematurely. In some cases, however, reversion to a Fix+ phenotype occurred after 4 to 6 wk. Bacteria released into newly infected cells in these nodules showed normal development into bacteriods.