Penetration of the Periderm of Red Raspberry Canes by Leptosphaeria coniothyrium

Umwounded raspberry canes were inoculated with Leptosphaeria coniothyrium. After penetration of the epidermis the fungus invaded the cortex readily. The accumulation of mycelium in this tissue lead to a partial digestion of the middle lamellae of the outermost cork layer within the polyderm. The fungus penetrated this single cell barrier through the openings between the separated cells and colonized the phelloid tissue between the first and second cork layer. After vigorous growth in this non-suberized tissue the fungus penetrated the second cork barrier in the same way as the first layer. This mode of penetration was repeated until the fungus had spread beyond the periderm and into the vascular tissues. The invasion process occurred rather slowly and was enhanced by weakening of the canes by defoliation at the time of inoculation.     

Anatomical study on the interaction between the root endophytic fungus <Emphasis Type="Italic">Heteroconium chaetospira</Emphasis> and Chinese cabbage

Chinese cabbage roots colonized by the dematiaceous fungal taxon Heteroconium chaetospira were previously found to become highly resistant to clubroot and Verticillium yellows. The dematiaceous fungus possesses an endophytic nature, but no detailed anatomical studies on endophyte–host plant interactions have so far been provided. Light and electron microscopy revealed that hyphae of H. chaetospira were abundant on and inside the root epidermal cells by 3 weeks following inoculation. The penetration pegs easily breached into epidermal cells, and the infection hyphae penetrated into cortical cells. Some appressorium-like swollen structures formed from intracellular hyphae, but no visible degradation of the host cell walls was evident where the hyphae contacted. No visible signs of host reactions and no invagination of the host plasma membrane around the hyphae were seen in the host cells. By 8 weeks following inoculation, masses of closely packed fungal cells had been formed in some cells of the epidermis and cortical layers, but further hyphal ingress was halted, mostly in the inner cortical cell layer. Thus, root vascular cylinders remained intact.     

Ultrastructural analysis of the behavior of the dimorphic fungus Microbotryum violaceum in fungus-induced anthers of female Silene latifolia flowers

Summary. The development of male organs is induced in female flowers of the dioecious plant Silene latifolia by infection with the fungus Microbotryum violaceum. Stamens in a healthy female flower grow only to stage 6, whereas those in an infected female flower develop to the mature stage (stage 12), at which the stamens are filled with fungal teliospores instead of pollen grains. To investigate these host–parasite interactions, young floral buds and fungus-induced anthers of infected female flowers were examined by electron microscopy following fixation by a high-pressure freezing method. Using this approach, we found that parasitic hyphae of this fungus contain several extracellular vesicles and have a consistent appearance up to stage 8. At that stage, parasitic hyphae are observed adjacent to dying sporogenous cells in the infected female anther. At stage 9, an increased number of dead and dying sporogenous cells is observed, among which the sporogenous hyphae of the fungus develop and form initial teliospores. Several types of electron-dense material are present in proximity to some fungi at this stage. The initial teliospores contain two types of vacuoles, and the fungus cell wall contains abundant carbohydrate, as revealed by silver protein staining. The sporogenous cell is probably sensitive to infection by the fungus, resulting in disruption. In addition, the fungus accelerates cell death in the anther and utilizes constituents of the dead host cell to form the mature teliospore. Correspondence and reprints (present address): Molecular Membrane Biology Laboratory, RIKEN, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan.     

A dorsiventral mycorrhizal root in the achlorophyllous<Emphasis Type="Italic"> Sciaphila polygyna</Emphasis> (Triuridaceae)

The star-like root system of the achlorophyllous Sciaphila polygyna (Triuridaceae) consists of roots up to 1.4 mm thick and 1 cm long seemingly radiating from a single origin. Internally, the roots show a bilateral symmetry when viewed in cross-section: the third root cell layer contains rather loose coils of the aseptate mycorrhizal fungus from the dorsal to the lateral sides, in contrast to the extremely dense coils of thin hyphae in its ventral part. Additionally, the hyphae develop vesicle-like swellings mainly in the central part of the dorsal side as well as the lateral parts of the third layer. The fourth root layer is anatomically heteromorphic, having exceptionally large cells, reaching up to 320×130 m in size (giant cells), in the lower lateral parts. The root-colonizing hyphae only degenerate in the fourth layer, most readily in the giant cells, where they may swell to 24 m in diameter, collapse and end as amorphous clumps. Hyphae in the third layer keep their definite structure. The structures are interpreted to be the result of a dynamic reaction of the root to the actual fungal penetration points in order to maximize the benefit from the subsequent colonization by compartmentation of the root tissue. The function of the third layer is to host the fungus and keep it alive within its cells, while mainly the giant cells serve for its digestion. Many indications suggest an arbuscular mycorrhiza for this association. Similarities and differences to other myco-heterotrophic species are discussed.     

两种类型栓皮栎软木细胞微观排列与形态特征

采用扫描电镜对秦岭北坡楼观台地区的厚皮、薄皮两种类型栓皮栎软木进行细胞微观构造观察分析,并与欧洲栓皮槠进行比较,以阐明厚皮、薄皮栓皮栎软木的相关特性,为中国栓皮栎软木的合理利用提供依据。结果表明:(1)两种类型栓皮栎软木细胞的排列结构较一致,均由内部中空的封闭型薄壁细胞紧密排列组成;在弦切面上呈蜂窝状排列,径切面和横切面上呈砖墙状排列;在径切面上,软木细胞侧高整齐地排列成行,且与树干轴向垂直;在横切面上,软木细胞侧高整齐地处于以树干轴为中心散发出来的射线上。(2)栓皮栎软木细胞大小、细胞壁和侧壁褶皱等受生长季节的影响;从软木细胞形态特征上看,厚皮类型软木细胞壁薄、细胞体积大,其软木质量优于薄皮类型。(3)与欧洲栓皮槠比较,发现厚皮类型栓皮栎早软木细胞棱柱高较小(20.6μm vs.(对比)30~40μm),软木细胞壁略厚(1.7μm vs.1~1.5μm),细胞实体积(细胞壁体积占细胞总体积比例)略大(18.75%vs.10%),厚皮类型栓皮栎软木比欧洲栓皮槠的软木质量差一些。(4)受树皮生长应力的影响,两种类型栓皮栎软木细胞侧高壁上多发生褶皱,早软木细胞褶皱严重,晚软木细胞没有褶皱,但在早晚软木交界或含有杂质处褶皱特别严重,表明厚皮类型软木细胞的侧壁褶皱程度高于薄皮类型。(5)对细胞形态特征及软木特性等的分析表明,薄皮类型栓皮栎软木质量比厚皮类型差,未来对软木资源的开发利用应更注重厚皮类型。     

Teliospores of smut fungi general aspects of teliospore walls and sporogenesis

Summary The concept and nomenclature for the elements of teliospore walls in smut fungi are presented and a survey of teliosporogenesis is given, as seen by light and transmission electron microscopy. Four developmental types are distinguished: the Ustilago, Microbotryum, Tilletia, and Entorrhiza type. In the Ustilago type, sporogenous hyphae are completely segmented into teliospore initials which are embedded in a hyaline matrix formed by gelatinised hyphal walls (found in species ofAnthracoidea, Cintractia, Heterotolyposporium, Kuntzeomyces, Macalpinomyces, Melanopsichium, Sporisorium, Testicularia, Tolyposporium junci, Trichocintractia, and species ofUstilago infecting members of the family Poaceae). In the Microbotryum type, septate sporogenous hyphae are also completely segmented into teliospore initials, however, they are not surrounded by a hyaline matrix (Microbotryum, Sphacelotheca, Ustilago spp. infecting dicotyledons). A yeast-like budding of teliosporogenic cells is observed for some species ofMicrobotryum, Sphacelotheca, andUstilago infecting dicotyledons. In the Tilletia type, teliospores differentiate locally in the sporogenous hyphae, in an apical or intercalary position, without a hyaline matrix (Conidiosporomyces, Doassinga, Entyloma, Erratomyces, Ingoldiomyces, Neovossia, Oberwinkleria, Rhamphospora, Tilletia). In all these types, the teliospore initials first develop a hyaline sheath under which the ornamentation, the exosporium, sometimes a middle layer, and the endosporium are successively deposited by the fungal cell. In the Entorrhiza type, the teliospores develop inside vital host cells with the wall of the sporogenous hypha included into the teliospore wall. The fungus develops a middle layer and an electron-transparent endosporium inside the hyphal wall while a layer forming the ornamentation is deposited onto the hyphal wall, probably by vesicles of dictyosomes of the host cell.Part 164 in the series Studies in Heterobasidiomycetes from the Botanical Institute, University of Tübingen     

Cytochemical evidence of a fungal cell wall alteration during infection of Eucalyptus roots by the ectomycorrhizal fungus Cenococcum geophilum

When the ectomycorrhizal fungus Cenococcum geophilum changes from a saprophytic to a symbiotic stage, its cell wall structure becomes simplified. The external hyphal wall layer which, in the saprophytic stage, is highly reactive to the Gomori-Swift test becomes poorly reactive and can no longer be distinguished from the internal wall layer in the Hartig net hyphae. The intensely stained external wall layer was also absent from pure cultures of Cenococcum geophilum grown on a medium with a low sugar content. This cell wall alteration could be due to a decrease in the amount of melanin or of melanin plus cystine-containing proteins. This change may be necessary for increased nutrient exchange between symbionts through hyphal walls.     

Arthopyrenia endobrya,spec. nov., eine hepaticole Flechte mit intrazellulärem Thallus aus Brasilien

Arthopyrenia endobrya from Southern Brazil is illustrated and described as a new species of lichens. The thallus is composed of filamentous green algae loosely surrounded by fungal hyphae. Both symbionts grow endophytically within the leaf cells of two species ofLejeuneaceae (Hepaticae). The algae and hyphae penetrate the cell walls of the host by means of fine perforations. The ascocarps develop between the leaves and perforate them with their apical region. The classification as a member of the genusArthopyrenia is preliminary.

     

Gradient of photosynthetic pigments in the bark and leaves of lilac (Syringa vulgaris L.)

The concentration of chlorophyll and a carotenoids in the bark of stems of different age and in the leaves of lilac (Syringa vulgaris L.) was determined. The thickness of bark changes with the age of the stems, ranging from 0.73 mm in the current-year stems to 1.22 mm in 3-year-old ones. Chlorophyll and carotenoids were present through the whole thickness of the bark, except the cork. It was found that chlorophyll and carotenoids are located mainly in the outer layer of the bark, immediately under the cork, to a depth of 400 μm. In this layer the chlorophyll a/b ratio is the highest and the content of chlorophyll is four times larger than that of carotenoids. When penetrating deeper into the bark, the content of chlorophyll and carotenoids as well as the chlorophyll a/b ratio diminishes. Investigations of the leaves showed that most of the chlorophyll is found in the palisade parenchyma, the chlorophyll a/b ratio is the highest in the upper layer. The highest concentration of chlorophyll in the bark is 0.44 mg·dm⁻² and in leaves −1.2 mg⁻²·dm⁻². The highest value of the chlorophyll a/b ratio in the bark is 3.8, and the lowest 0.5, while in the leaves it varies from 4.5 to 3.8 Low values of the chlorophyll a/b ratio are due to the shade conditions existing in the bark and they are evidence of very great differentiation of light conditions within it.     

Endophyte differentiation inCasuarina actinorhizae

Summary This is an ultrastructural study of development of infected cells in nitrogen fixing root nodules ofCasuarina spp. While several aspects of development are similar to those found in many other actinorhizae, unusual aspects of development of the host cell and differentiation of the endophyte inCasuarina are correlated with unusual changes in the wall of the infected cell. Instead of vesicles the endophyte forms atypical hyphae in mature infected cells. These unusual hyphal forms are termed intracellular hyphae. Intracellular hyphae are nonseptate hyphae which originate and terminate within the same host cell, and have a varying diameter and a multidirectional growth and branching pattern. A laminate surface layer previously undescribed on hyphae ofFrankia is a feature common to mostCasuarina endophytic hyphae and is probably similar chemically to the laminae comprising the multilamellate envelope of endophytic vesicles in other actinorhizae.This paper is Florida Agricultural Experiment Station Journal Series No. 7350.     

Surface interactions of Fusarium graminearum on barley

The filamentous fungus Fusarium graminearum, a devastating pathogen of barley (Hordeum vulgare L.), produces mycotoxins that pose a health hazard. To investigate the surface interactions of F. graminearum on barley, we focused on barley florets, as the most important infection site leading to grain contamination. The fungus interacted with silica‐accumulating cells (trichomes and silica/cork cell pairs) on the host surface. We identified variation in trichome‐type cells between two‐row and six‐row barley, and in the role of specific epidermal cells in the ingress of F. graminearum into barley florets. Prickle‐type trichomes functioned to trap conidia and were sites of fungal penetration. Infections of more mature florets supported the spread of hyphae into the vascular bundles, whereas younger florets did not show this spread. These differences related directly to the timing and location of increases in silica content during maturation. Focal accumulation of cellulose in infected paleae of two‐row and six‐row barley indicated that the response is in part linked to trichome type. Overall, silica‐accumulating epidermal cells had an expanded role in barley, serving to trap conidia, provide sites for fungal ingress and initiate resistance responses, suggesting a role for silica in pathogen establishment.     

Gut passage times in Gammarus pulex (Crustacea,Amphipoda) and aspects of summer feeding in a stony stream

Gut passage times in Gammarus pulex (Crustacea, Amphipoda) were calculated by counting and measuring voided faecal pellets. Following feeding on elm leaves conditioned in a stream, or summer fine detritus from the same source, calculated gut passage times were usually short, about 2 h or less at 15 °C. Using harder oak and beech leaves, not previously conditioned in the stream, apparent gut passage times were much longer, 8–48 h, but since intermittent feeding occurred these figures are not comparable to the others.In connection with summer feeding of the animal in the stream, the microbiological status of the fine detritus there was studied. It contained fungal hyphae, which were mostly empty, viable fungal spores of terrestrial derivation, and bacteria, all largely carried on fragments of vascular plant tissues. In experiments, such fungal spores (of Aureobasidium pullulans and of Mucor sp.), incorporated into fine detritus, were not digested by the animal. The bacterium Bacillus cereus was present in the fine detritus and when the latter was consumed it survived passage through the gut of the animal. Using B. cereus as a proportion marker it was concluded that other unicellular bacteria in the fine detritus were not digested either. In other experiments, not immediately related to the summer season, nutrient extraction by the animal from hyphae of the fungus Nectria lugdunensis was examined; it probably occurs through sub-microscopic pores connecting the cells. This mode of extraction may apply when the animal consumes vascular plant tissues.     

Chalara elegal-Infected Tobacco Roots: Ultrastructural Observations on in vitro Host-Fungus Relationships

Evidence, based on ultrastructural observations of stages involved in root infection oi Nicotiana tabacum cv. Xanthi n.c. in vitro by the black root rot fungus Chalara elegans, indicates that host cells from various layers react differently when challenged by the pathogenic fungus. All the host responses observed were associated with host cell wall modifications. Host reaction to fungal invasion occurring in the epidermal cells was limited to a disorganization of the cytoplasm. In the hypodermal cell layer, fibrillar cell wall outgrowths and wall thickenings were the earliest and the most obvious host reactions. In parenchymal cells, the host reacted by depositing papilla-like wall appositions directly adjacent to the infecting hyphae; with secondary infection of these cells, a densely staining material was laid down, mainly around the distal region of the infecting hyphae. In all these tissues, infection also led to disorganization of the host cytoplasm. Colonization of the endodermis did not lead to any rapid lethal modifications in either the host or the fungus, and a biotrophic-like state seemed to occur at this stage of the infection. No hyphal infection occurred in the central cylinder.     

The hyphae ofUromyces appendiculatus within the leaf tissue after high pressure freezing and freeze substitution

Summary The fine structure of the intercellular dikaryotic hyphae of the biotrophic fungusUromyces appendiculatus was studied. High pressure freezing and freeze substitution were used to achieve a closer approximation of the native state than with conventional fixation and dehydration techniques. In addition to organelles previously described in rust fungi, heavily decorated multivesicular bodies (star bodies) were found close to the nuclei. Two types of tubular-vesicular complexes were distributed randomly within the cytoplasm of the hyphae. Furthermore, a more or less pronounced brush-like fibrillar layer on the hyphal walls was detected. The possibility that the latter two structures are correlated with the biotrophic phase of this fungus is discussed.Abbreviations TVC tubular-vesicular complex - MVB multivesicular body - M mitochondrion - N nucleus - NP nuclear pore - S septum - MT microtubule     

Identification of the endophypte ofDryas andRubus (Rosaceae)

Summary Root nodules ofDryas drummondii are of the coralloid type (Alnus type). The endophyte is present in the middle cortical cells of the root-nodule tissue. Transmission electron micrographs revealed an actinorhizal endophyte with septate hyphae and non-septate spherical or ovoid vesicles. Vesicles always possess at the base a septum; septa formation in the endophyte is always associated with the presence of mesosomes. Branching of the endophyte is not necessarily correlated with septum formation. Hyphal structures are more prominent in the apical part of the root nodule and vesicles are more numerous in a broad zone below this. In the middle and towards the base of the root nodule the endophytic structures appear in a stage of disintegration. Vesicles appear in a broad region near the periphery of the host cell and regularly show no strict orientation towards the host-cell wall. In the center of the host cells only hyphae occur. In the intercellular spaces between the host cells theFrankia endophyte produces spore-like structures although the outline of the sporangia is often faint.The coralloid root ofRubus ellipticus shows characteristically a basal rootlet initiated below the dichotomous branching of the nodular lobes, but extending beyond the root nodule. The endophyte is only present in the outer cortex of the root nodule in a 1–2 cell wide layer. This endophytic layer is bounded, internally as well as externally, with a 4–5 cell wide layer of tannin-filled host cells. The implications of this situation are discussed. Tannin-filled cells occur regularly inRubus species and their arrangement has been used for taxonomic purposes within the genus. TheRubus endophyte is aFrankia species with septate hyphae and distinctly septate spherical vesicles. The ultrastructure of the vesicles of theRubus endophyte is very similar to that of theAlnus endophyte.     

Effects of population density on alienicolae of Aphis fabae Scop.: The expression of migratory urge among alatae in the field

Inspection of naturally or artificially infected Hevea roots showed that Forms lignosus can penetrate undamaged roots directly, but does so more readily through wounds or natural openings like lenticels, or through the bases of lateral roots and bark scales. Therefore, Pomes-infected trees should be identified by leaf symptoms rather than by uncovering and inspecting roots, as this generally leads to root injury, which facilitates fungal penetration. Initial fungal entry into host tissue appears to be by mechanical pressure alone, but deeper penetration is through the action of extracellular enzymes. The fungus remains intercellular in the cortex but is intracellular in the woody tissue. Ray cell walls are penetrated mechanically, but the xylem through pits. The time taken for various stages of infection to occur is assessed. The amount of damage done by the fungus to roots and the blocking of xylem vessels by tyloses suggest that yellowing, curling and buckling of leaves on infected trees are drought symptoms and not a reaction to fungal toxins. The host reacts to the invasion of the cortex by forming a cork cambium and to the invasion of the woody tissue by blocking individual cells with phenols and resins, which could be important when breeding disease resistant Hevea root stocks.     

Observations on the ultrastructure of the uredinial stage ofPuccinia polypogonis onPolypogon monspeliensis

The ultrastructure of the uredinial stage of the rust fungus,Puccinia polypogonis onPolypogon monspeliensis is described, using scanning and transmission electron microscopy. This study examined the urediniospores, intercellular hyphae, and haustoria of the fungus. The formation and structure of urediniospores is similar to those of otherPuccinia species. The ultrastructure of intercellular hyphae and haustoria is similar to those of other rust fungi, but with some differences. No modifications are observed in the wall of the haustorial mother cells during penetration. A collar is found only around old haustoria. In most cases, one nucleus is detected inside the haustorial body and no nucleoli are seen in the nuclei of intercellular hyphae and haustoria. The host-parasite interface, including extrahaustorial matrix and extrahaustorial membrane, is also discussed and compared with those of other rust fungi.     

An electron microscopic observation of conidium and hypha of Erysiphe graminis hordei

Summary The fine structure of conidia and hyphae ofErysiphe graminis hordei, attacking leaves of barley, were investigated. The cell walls of conidia and hyphae were relatively thin and consisted of two layers, the inner and outer layers. The surface of conidia was not smooth and the thickness of cell walls was irregular. A nucleus, mitochondria, endoplasmic reticula and vacuoles in plasma were identified. The vacuoles in conidia were tightly packed with fine granules. Such granules in vacuoles, however, were not observed in hyphal cells.A lamellar structure was located in conidia, but not in hyphal cells. This structure may be specific in conidia of this fungus, but its function is not yet known. Many glycogen granules were observed in endoplasm of conidia, which were scattered or congregated in groups. In hyphae, however, they were extremely few. Hyphal septa were connected directly with the inner layer of cell walls. These had simple septal pore. The Woronin bodies were detected in the endoplasm in the vicinity of hyphal septa.Contribution No. 192.     

A newLeptographium species associated withTomicus piniperda in south-western China

Tomicus species (Coleoptera: Scolytidae) are serious pests of pines with a wide distribution in Europe, Asia and America. In Yunnan, south-western China,T. piniperda has destroyed more than 0.5 million ha ofPinus yunnanensis in the past 15 years. A blue stain fungus belonging to the genusLeptographium is associated with both the shoot-feeding and trunk-attacking stages of the beetle's life cycle. The fungus is morphologically similar to the anamorph ofOphiostoma crassivaginatum and toL. pyrinum, which are both characterised by short robust conidiophores and hyphae covered by a granular layer. Both these species have been isolated from conifers and are associated with insects. After comparing the fungus fromT. piniperda with similarLeptographium species, using light and scanning electron microscopy, we concluded that it represents a new taxon, which is described here asL. yunnanense sp. nov.     

濒危植物海南风吹楠营养器官解剖结构特征

该研究采用石蜡切片和光学显微技术,对海南风吹楠营养器官的解剖结构及其对环境的适应性进行了探讨。结果表明:海南风吹楠为典型异面叶,叶片中脉发达,中部分化出髓,上表皮外侧具角质层,内侧具1层内皮层,下表皮外侧无角质层,有气孔器分布,气孔器为双环型,略下陷;栅栏组织3~4层细胞,海绵组织4~6层细胞。茎的初生结构中表皮轻微角质化,维管束为外韧型,8~10个初生维管束围绕髓排列为1轮;茎的次生结构中,表皮外部角质层加厚,维管柱紧密排列连成环状,次生韧皮部和次生木质部发达,形成层细胞3~5层。根的初生结构中表皮细胞外壁加厚,外皮层细胞体积大,形状不规则,内侧具1层形成层,内皮层具凯氏带,初生木质部为多原型,呈辐射状排列。根的次生结构中木栓层细胞5~6层,木栓层内侧具1层木栓形成层,栓内层细胞3层。海南风吹楠营养器官具有一定耐阴和耐旱结构特征,同时与其生活的热带雨林沟谷中高温荫湿的环境相适应。