THE SUBEPIDERMAL FUNGI OF CEREAL GRAINS

Examination of samples received in 1947 and 1948 showed that a subepidermal mycelium occurred in normal wheat grains from almost all the wheat-growing areas of the world. The amount of mycelium varied widely: there are indications that the degree of infection is dependent on the atmospheric humidity during the ripening of the grain. No subepidermal mycelium was found in wheat grains from some crops grown under irrigation.     

天麻种子与兰小菇共生萌发过程中超微结构变化研究

天麻Ｇａｓｔｒｏｄｉａｅｌａｔａ种子与兰小菇Ｍｙｃｅｎａｏｒｃｈｉｄｉｃｏｌａ的共生萌发试验表明兰小菇可与天麻种子共生促进天麻种子萌发并形成原球茎。菌丝自胚柄端的柄状细胞侵入天麻种子原胚,其分布被限制在天麻原球茎基部的柄状细胞、外皮层细胞和内皮层细胞内,均被电子透明物质和原球茎细胞质膜包围而与原球茎细胞质相隔离。菌丝在外皮层细胞中形成菌丝结,在内皮层细胞中则被消化,形成扁化、衰败的菌丝或菌丝四块。含有衰败菌丝的原球茎细胞可被菌丝重新定殖,新近定殖的菌丝又被原球茎细胞消化。     

天麻种子与兰小菇共生萌发过程中超微结构变化研究*

天麻Ｇａｓｔｒｏｄｉａｅｌａｔａ种子与兰小菇Ｍｙｃｅｎａｏｒｃｈｉｄｉｃｏｌａ的共生萌发试验表明兰小菇可与天麻种子共生促进天麻种子萌发并形成原球茎。菌丝自胚柄端的柄状细胞侵入天麻种子原胚,其分布被限制在天麻原球茎基部的柄状细胞、外皮层细胞和内皮层细胞内,均被电子透明物质和原球茎细胞质膜包围而与原球茎细胞质相隔离。菌丝在外皮层细胞中形成菌丝结,在内皮层细胞中则被消化,形成扁化、衰败的菌丝或菌丝四块。含有衰败菌丝的原球茎细胞可被菌丝重新定殖,新近定殖的菌丝又被原球茎细胞消化。     

The infection biology of Fusarium graminearum: defining the pathways of spikelet to spikelet colonisation in wheat ears

Fusarium graminearum is one of the main causal agents of Fusarium Ear Blight on wheat. How the pathogen colonises the entire ear is not known. There is controversy over whether this mycotoxin producing pathogenic fungus invades wheat floral tissue using a necrotrophic or another mode of nutrition. A detailed microscopic investigation has revealed how wild-type fungal hyphae, of the sequenced strain PH-1, colonised susceptible wheat ears and spread from spikelet to spikelet. At the advancing infection front, colonisation of the host cortex occurred ahead of any vascular colonisation and the hyphae adapted to the available intercellular space between host cells. Intercellular hyphae then became abundant and host cells lost their entire cellular contents just prior to intracellular colonisation. No host cells died ahead of the infection. However, while these deep cortex infections progressed, just below the surface the highly photosynthetic chlorenchyma cells were observed to have died prior to colonisation. Behind the infection front, hyphae were abundant in the vasculature and the cortex, often growing through the pit fields of thick walled cells. This high level of inter- and intracellular fungal colonisation resulted in the collapse of the non-lignified cell-types. In this middle zone of infection, hyphal diameters were considerably enlarged. Far behind the infection front inter- and intracellular hyphae were devoid of contents and had often collapsed. At later stages of infection, the pathogen switched from predominately vertical to lateral growth and accumulated below the surface of the rachis. Here the lignified host cell walls became heavily degraded and hyphae ruptured the epidermis and produced an aerial mycelium.     

天麻种子萌发过程中与其共生真菌石斛小菇间的相互作用*

天麻Gastrodiaelata种子与石斛小菇Mycenadendrobii的共生萌发试验表明,石斛小菇可与天麻共生,促进天麻种子发芽并形成原球茎。菌丝主要分布于原球茎的柄状细胞、外皮层细胞和内皮层细胞,在外皮层细胞中形成菌丝结,内皮层细胞中的菌丝则被消化。原球茎细胞中的菌丝均被电子透明物质和原球茎细胞质膜包围而与原球茎细胞质相隔离,菌丝进一步液泡化并最终被水解。含有衰败菌丝的原球茎细胞常被菌丝重新定殖。这一菌丝被消化及菌丝的重新定殖过程在整个原球茎发育过程中可不断重复发生。     

天麻种子萌发过程中与其共生真菌石斛小菇间的相互作用

天麻Gastrodiaelata种子与石斛小菇Mycenadendrobii的共生萌发试验表明,石斛小菇可与天麻共生,促进天麻种子发芽并形成原球茎。菌丝主要分布于原球茎的柄状细胞、外皮层细胞和内皮层细胞,在外皮层细胞中形成菌丝结,内皮层细胞中的菌丝则被消化。原球茎细胞中的菌丝均被电子透明物质和原球茎细胞质膜包围而与原球茎细胞质相隔离,菌丝进一步液泡化并最终被水解。含有衰败菌丝的原球茎细胞常被菌丝重新定殖。这一菌丝被消化及菌丝的重新定殖过程在整个原球茎发育过程中可不断重复发生。     

An ultrastructural study of pale eumycetoma grains

The electron microscopic appearances of grains from seven patients with pale grain eumycetoma infections have been studied. The infecting fungi were Pseudallescheria boydii (2), Fusarium sp. (1), Acremonium kiliense (1), a non-sporing mould (2) and Trichophyton violaceum (1). P. boydii grown in vitro and grains from a Madurella mycetomatis infection were used for comparison. The most important ultrastructural features of the pale eumycetoma grains were the gross thickening of the fungal cell walls maximal at the periphery of the grain, the predominance of grossly disorganised hyphae and the appearance of cytoplasmic membrane systems. In some areas adjacent cell walls appeared to fuse. These changes may account for some of the well recognised difficulties in isolating organisms from eumycetoma grains and treating the infections with antifungal drugs.     

Cerato-platanin protein is located in the cell walls of ascospores, conidia and hyphae of Ceratocystis fimbriata f. sp. platani

Cerato-platanin (CP), a protein of about 12.4 kDa from Ceratocystis fimbriata f. sp. platani (Cfp), accumulated in the mycelium and was located in the cell walls of Cfp ascospores, hyphae and conidia suggesting that this protein had a role in forming the fungal cell wall apart from the already known fact that it is secreted early in culture and elicits phytoalexin synthesis and/or plant cell death. The finding was obtained with three immunological techniques: a quantitative ELISA which determines the amount of CP in the mycelium, an immunofluorescence assay, and immunogold labelling to define the exact localization of CP in the Cfp cells.     

A discovery of riphean heterotrophs in the Lakhanda group of Siberia

New fossil remains have been discovered from the well-known Lakhanda Microbiota (1015–1025 Ma, Uchur-Maya Region, Southeastern Siberia). The microfossils have characters observed in microscopic fungi, such as a reticulate mycelium, formed by anastomizing hyphae of non-cellular structure and of variable width. The fungal mycelium shows that hyphae grew in a certain direction, both forwards and backwards. As their length increased, the hyphae became curved and merged with neighboring hyphae to form enclosed spaces. The presence on hyphae of knoblike trapping structures and secretion of adhesive enzymes suggest a similarity with modern nematophagous fungi. Microorganisms associated with the adhesive hyphae consist of colonial green unicellular algae and thin bacterial sheaths, which may indicate mutually beneficial relationships between morphologically and biologically different partners. Microfossils of fungal origin are systematically described. They include Aimonema ramosa gen. et sp. nov. and the green unicellular alga Eoprotoderma neruenica gen. et sp. nov., forming a symbiotic association.     

Laser microdissection of fungal septa as visualised by scanning electron microscopy

Laser microdissection has been proven a successful technique to isolate single cells or groups of cells from animal and plant tissue. Here, we demonstrate that laser microdissection is suitable to isolate subcellular parts of fungal hyphae. Dolipore septa of Rhizoctonia solani containing septal pore caps were cut by laser microdissection from sections of mycelium and collected by laser pressure catapulting. Subsequently, microdissected septa were visualised using a wheat germ agglutinin labelling of cell walls, septa and septal pore caps and scanning electron microscopy. The use of laser microdissection on fungal cells opens new ways to study subcellular fungal structures and the biochemical composition of hyphal cells.     

EXPERIMENTS ON THE EFFECT OF CENTIMETRE-LENGTH ELECTROMAGNETIC WAVES ON WOOD-DESTROYING FUNGI

In an attempt to devise a practical method of killing wood-destroying fungi, mycelia of Coniophora puteana and Merulius lacrymans were exposed to the beamed radiation from a standard Service radar transmitter transmitting pulses of radiation of wave-length 9.1 cm. Growth of Coniophora puteana on malt agar films on glass slides was checked. Many superficial hyphae were killed. Exposures up to I hr. did not kill the mycelium of either fungus when growing on malt agar slopes or plates, or wood blocks. The only obvious effect was a check in growth whenever drying of the mycelium occurred.
It is concluded that the rays have no lethal effect and injure the fungi only through drying of the mycelium due to the increase in temperature which they bring about.     

天麻种子／原球茎和营养繁殖茎被菌根真菌定殖后的细胞分化

天麻（Gastrodia elata Bl.)种子可与紫萁小菇（Mycena osmundicola Lange),兰小菇（M.orchidicola Fan et Guo)等一类小菇属真菌共生萌发形成原球茎。侵入种皮的菌丝集结在柄状细胞外周的胚柄残迹中,首先侵入胚的柄状细胞,然后自柄状细胞侵入其他原胚细胞。原胚细胞发生功能分化,形成菌丝结细胞和消化细胞,初被菌丝定殖的原胚细胞具有消化菌丝的功能,随后,部分原胚细胞逐渐被菌丝充满,充育成菌丝结细胞。菌丝由菌丝结细胞进一步侵入消化细胞后最终被消化。由原球茎分化形成的营养繁殖茎（以下简称营繁茎）进一步被蜜环菌（Armilariella mellea(Vahl.Fr.)Karst.)定植,蜜环菌与紫箕小菇的菌丝同时存在于营繁茎中,但两菌相遇时都停止蔓延,互不交错侵染。     

Direct observation of fungal aggregates in sand dune soil.

The mycorrhizal fungus Glomerus in association with bean hosts, Phaseolus vulgaris L., growing in pot cultures and grass hosts, Calamovilfa longiflora (Hook). Scribn and Andropogon sp. growing on Lake Huron sand dunes produced extensive external mycelium. This mycelium was the dominant factor in the aggregation of soil particles. Light and scanning electron microscope studies indicated that the sand grains were attached to the hyphae. An amorphous deposit was often present at the interfaces of sand grains and hyphae. It appeared to act as an adhesive. Staining procedures indicated that this material contained polysaccharide. Other microogranisms were observed in association with the Glomus hyphae and the amorphous deposits.     

Cytodifferentiation of the Seeds (Protocorms) and Vegetative Propagation Corms Colonized by Mycorrhizal Fungi

The stipecell, subepidermal parenchyma cells and inner cortical parenchyma cells were differentiated from Gastrodia elata Bl. seed and protocorm cells when they were colonized by the fungal hyphae of Mycena osmundicola Lange and M. orchidicola Fan et Guo. The hyphae aggregated in the suspensor remnant surrounding stipecell, primarily penetrated the stipecell, and then colonized the embryo of seed. Stipecell is the unique invading site of the hyphae. Subepidermal parenchyma cells containing pelotons of hyphae is also a kind of passage cells of hyphae, but, when primarily colonized by hyphae, they can degenerate a little of hyphae. The hyphae colonizing inner cortical parenchyma cells were totally degenerated, and the function of inner ocrtical parenchyma cells is digestive. The vegetative propagation corms, which differentiated from protocorms, were recolonized by Armilariella mellea (Vahl:Fr.) Karst., and the hyphae of A. mellea and M. osmundicola were found in the same cell, but there is a layer of cells uncolonized by mycorrhizal fungal hyphae. This means the two fungal species can not crisscross colonize the cell of G. elata.     

ELECTRON MICROSCOPY OF THE HOST-PARASITE RELATIONSHIPS IN STEM RUST OF WHEAT

Ehrlich , H. G., and Mary A. Ehrlich . (Duquesne U., Pittsburgh, Pa.) Electron microscopy of the host-parasite relationships in stem rust of wheat.—Amer. Jour. Bot. 50(2): 123–130. Illus. 1963.—A series of micrographs showing intercellular dikaryotic mycelium, haustorial mother cells, stages in haustorial formation, and haustoria within host cells are presented in the present report. Of special interest and potential significance in a study of obligate parasitism is an encapsulation ranging from 800 to 3400 A in thickness which surrounds the haustorium, but which is not present around the intercellular hyphae. The encapsulation completely encases the haustorium proper; it is bounded on the inside by the cell wall of the haustorium, and its thin membranous outer margin abuts directly on the protoplast of the host cell. The nature of the material composing the encapsulation is uncertain, but it appears to originate from the haustorial protoplast, and at least a portion of it may be fungal cytoplasm. This newly described structure represents the actual interface between the host and pathogen. Small vesicles which seem to originate from the outer margin of the encapsulation are sometimes found in the host cytoplasm surrounding apparently vigorous haustoria. The vesicles are bounded by a membrane and contain particulate material.     

Fungal endophytes in Astromyelon-type (Sphenophyta,Equisetales, Calamitaceae) roots from the Upper Pennsylvanian of France

A distinctive fungal endophyte, Cashhickia acuminata nov. gen. et sp., is described from permineralized calamite roots from the Upper Pennsylvanian Grand-Croix cherts of France. Heavily infected roots contain numerous intracellular hyphae in the outer cortex that arise from a meshwork-like mycelium extending between cortical cells. All intracellular hyphae are oriented toward the root center; none occur on the inner periclinal host cell walls. Other roots of the same type show localized infection by this fungus in which isolated cortical cells contain or give rise to intracellular fungal growth. Within the cortical cells are host responses in the form of callosities that indicate the roots were alive at the time of infection. Other endophytes are present in the same host tissue but are less frequent. The discovery of this association provides the first detailed account on the morphology of a Carboniferous fungal root endophyte, as well as the spatial distribution within the host, and infection pathways within the cortical tissues.     

Cytological Study of Wheat Spike Infection by Bipolaris sorokiniana

The infection of wheat spikelets by Bipolaris sorokiniana , the causal agent of black point on grains and grain shrivelling, was examined by light and electron microscopy. Conidia of the pathogen germinated 6–12 h after inoculation on the surfaces of the different spike tissues. Extracellular sheaths were observed on germ tubes and appressoria attached to the surfaces of lemma, palea and seeds, but were only scarcely detected on the surface of conidia. Appressoria, frequently found over grooves, formed penetration hyphae invading the epidermal cell walls. Infection process was similar on the surface of the lemma, palea and glume. Growth of the fungus in the epidermal and parenchyma cells was found predominantly in the cell walls, and hyphae also extended intercellularly and intracellularly. Infection of seeds appeared to occur via two ways: (i) direct infection of the outer layers of the cell walls of the pericarp and (ii) through entering the stigma into the pericarp cells. Secretion of host cell wall hydrolytic enzymes at the apex of the penetrating hyphae may facilitate the spread of the fungus. In addition, toxins secreted by the fungus might explain the rapid death of host cells in contact with or distant to fungal cells. A host response to fungal infection involved the development of appositions between cell wall and plasma membrane in cells adjacent to fungal cells. Fungal hyphae were sometimes also surrounded by electron dense material.     

Development of Early Infection Structures of Puccinia recondita f. sp. tritici in Non-host Cereal Species

The development of infection structures, derived from urediospores of Puccinia recondita f.sp. trilici in nearisogenic lines of susceptible and resistant wheat, and in non-hosts (viz. maize, oat, sorghum and barley), was examined by fluorescence microscopy and scanning electron microscopy (SEM). The infection structure formation on and in five cereal species follows a similar pattern. In sorghum, fungal development is arrested at the stage of substomatal vesicle formation, while, in maize, most fungal structures collapse during the stage of primary hypha development. By contrast, in wheat, barley and oat, the fungus forms many branched infection hyphae and haustorial mother cells.     

ANATOMY OF THE SEED OF CONVOLVULUS ARVENSIS

Sripleng , Aksorn , (Kasetsart U., Bangkok, Thailand), and Frank H. Smith . Anatomy of the seed of Convolvulus arvensis. Amer. Jour. Bot. 47(5) : 386—392. Illus. 1960.–The anatropous ovule has a small, ephemeral nucellus covered by a massive integument. Shortly after fertilization, a lateral pouch develops from the upper portion of the embryo sac toward the dorsal side of the ovule and then downward. This leaves a partial integumentary septum in the base of the seed. The cellular endosperm is mostly absorbed by the embryo. Two—6 cell layers persist on all sides of the seed except below the cotyledons on the dorsal side where larger amounts persist. Over most of the seed the dermatogen develops into an epidermis that consists in part of groups of thick-walled elongate cells that produce the papillose appearance of the mature seed. The cells beneath the dermatogen divide periclinally and form 2 layers. The outer layer undergoes anticlinal divisions and differentiates a subepidermal layer of small, rectangular, thick-walled cells that become lightly lignified and suberized. The cells of the inner layer undergo some anticinal and periclinal divisions, elongate and differentiate as palisade sclerenchyma. The inner layers of the integument consist of parenchyma cells that are crushed and partially absorbed at maturity. The pad on the basal end of the seed, between the hilum and micropyle, is derived from a multiple epidermis that is differentiated into several layers of rectangular cells and a layer of palisade sclerenchyma. The subepidermal and palisade layers found over other parts of the seed dip beneath the pad.