Types Of Hyphae Research Articles

Penetration of Hyphae of Sclerotinia sclerotiorum by Coniothyrium minitans Without the Formation of Appressoria

AbstractIn a study using scanning electron microscopy (SEM), the mode of hyperparasitism of Coniothyrium minitans on its host Sclerotinia sclerotiorum was investigated. The SEM micrographs confirm previous reports, from light microscopic studies, that hyphal tips of C. minitans invade the host hypha by direct penetration, without developing appressoria, and that indentation of the host cell wall at the point of penetration is often evident. There is no functional distinction between amain branch and a side branch hypha of the hyperparasite and tips of either type of hyphae are capable of invading host hyphae by direct penetration.

Growth and form in lower plants and the occurrence of meristems

Fungi and streptomycetes have a similar morphology and in both groups branching appears to be regulated in a similar manner. Both types of hyphae grow by tip extension but streptomycete hyphae never attain the extension rates commonly observed for fungi. Fungal hyphae are able to attain high rates of extension because a very large volume of protoplasm contributes to tip growth and because a vesicular growth system facilitates the rapid assembly of the tip wall. Growth of fungal and streptomycete mycelia involves the duplication of a physiological unit of growth which consists of a tip and a portion of hypha whose average length remains constant. However, it is not clear that growth of such mycelia is truly modular. Although hyphal fusions within a mycelium are common in higher fungi their significance in the organism’s life style is not known. Growth in lower green plants, especially algae, is considered and the question of whether coenocytic algae are modular or not is discussed.

Sap stain in Antiaris africana, an economically important tropical white wood

MANY countries lose thousands of pounds annually through natural staining of valuable wood. Usually the organism which causes staining is the fungus Botryodiplodia theobromae Pat1. Field and laboratory experiments have shown that Antiaris africana becomes stained blue within 4 d of felling2,3. The fungus enters the cut surface of the wood through the vessels and within 2 d heavily colonises the surrounding vasicentric parenchyma cells. Infection of ray cells occurs through the vasicentric parenchyma cells1. The fungus has two types of hyphae: some are stout and brown in colour, others are thin and hyaline. The brown hyphae are predominantly found in vessels, tracheids and fibres (Fig. 1), whereas the parenchyma cells are heavily infected by the hyaline hyphae.

The concentric bodies of lichenized fungi

1. Concentric bodies have been detected in the mycobionts of at least forty-three species of lichens, and their presence in two non-lichenized fungi is reported here for the first time. The structure of the bodies appears to be closely similar in all species. 2. A detailed examination of the concentric bodies in electron micrographs of thin sections of Peltigera aphthosa Willd, indicates that the bodies are basically isodiametric in organization. The designation “concentric bodies”, a translation of the term “konzentrische Korper” first used by Peveling (1969a), is therefore preferred to the original name “ellipsoidal bodies” (Brown and Wilson, 1968). 3. Each concentric body is composed of two zones of osmiophilic material surrounding an electron-transparent core. The inner zone is limited internally by a membrane-like boundary. The outer zone has a variable appearance, but often contains radially arranged stainable structures which appear as lamellae in tangential sections. Concentric bodies may collapse under stress into discs with elimination of the core but without apparent rupture of the surrounding material. It is concluded that the bodies are empty or filled with gas or liquid. 4. The bodies occur singly or in clusters and are frequently surrounded by electron-transparent haloes. Clusters of bodies lie within a distinctive matrix which is almost invariably associated with the cell nucleus. 5. Concentric bodies have been found in all types of hyphae in the lichen thallus but not in the asci or ascospores. 6. Interpretations of previous workers are discussed in relation to the present findings, and hypotheses as to the nature of the concentric bodies are put forward. 7. No information is as yet available concerning the origin, development and functions of the concentric bodies, and the question of their possible significance for the lichenized condition remains open.

Cultural Characters and Carpophore Constructi of Some Poroid Hymenomycetes^

The cultural characters and construction of the carpophores of 24 species of poroid Hymenomycetes were studied. The microstructures formed in culture and oxidase reactions of the cultures were compared with the microstructures present, the construction and type of decay of the carpophores from which they were made. Fhe type of interfertility of seven species was determined. Intercollection pairings of haploid mycelia derived from single basidiospores and the technique of dikaryotizing a large haploid mycelium growing in culture by pairing it with a small dikaryotic mycelium, were used to confirm the identity of different collections of eight different species. The literature on the classification, structure and anatomy of the carpophores and pure culture studies of Hymenomycetes. was reviewed. It was found that the 24 species were distributed among nine of the groups proposed by Nobles (1958) on the basis of their cultural characters. TTie structures formed in culture were also found to be present in the carpophores so that the carpophores could also be assigned to the some groups as their cultures. The carpophores did not indicate the same relationships as the cultures however. Differences in the micromorphological characters of hyphae and in the types of hyphae present in carpophores of species in the same group were found. Differences in construction of the carpophores were noticed in species with similar types of hyphae. Micromorphological characters of hyphae and the microstructures as well as the construction of the carpophores are constant for each species. Differences and similarity of micromorphological characters and construction of carpophores of different species are not adequately conveyed by the concept of hyphal systems.

Hyphal Characteristics of Certain Fungi in Wood

The diagnosis of decay in timber based upon microscopic characteristics of hyphae seen in wood appears to be of limited value and useful mainly in establishing the type of fungal infection and the degree of deterioration which is present. While a number of criteria may be established for the recognition of decay in wood, the presence or absence of certain symptoms may be applied only in a positive sense, owing to the habit of fungi. In this way, for example, while the occurrence of mycelium, bore holes or eroded pits in the wood may evidence decay, the absence of one or all of these does not necessarily infer that the specimen is free of decay. Similarly, while clamp connections are a characteristic of basidiomycetous hyphae, these structures are not produced regularly and in fact do not occur at all in the case of many Basidiomycetes. Thus the absence of buckles is of little significance and does not eliminate the possibility of members of this class being present. At the same time, because of the diverse growth reactions which may be obtained when fungi attack wood, a degree of variation in their morphology, as reported by different workers, is to be expected. In this laboratory, however, I have encountered what appears to be a faulty interpretation of observations, the details of which are the subject of this paper. Examination in this laboratory of sections taken from dark colored heartwood of western red cedar (Thuja plicata Donn) commonly reveals hyphae of various types within the wood. The more obvious are unbranched and three microns or more in diameter. They often proceed more or less at right angles to the tracheids (FIG. 1). At a higher magnification also, the hyphae are seen to be sharply constricted where they pass through walls. This type of hyphae was reported by McCready 2 to be typical of Poria weirii Murr. in cedar (FIG. 2). The

INVESTIGATIONS OF RHIZOCTONIA CROCORUM (PERS.) DC. IN RELATION TO THE VIOLET ROOT ROT OF CARROT

Violet root rot of carrot, caused by Rhizoctonia crocorum (Pers.) DC, appears in Ontario in midsummer, and by the fall progresses to cause deep lesions in the fleshy root of the carrot. Isolation of the fungus from diseased carrot was successful only from mature infection bodies. Of all the media tried meat–malt agar supported the best growth of R. crocorum. While three types of hyphae were produced only those of the subiculum propagated the fungus, and only the subiculum and sclerotia were capable of initiating a parasitic attack on carrots. R. crocorum can infect any part of a carrot root, does not require a wound infection court, and can spread uniformly over the carrot regardless of where primary infection occurs. Although the development of the carrot, the growth of R. crocorum, and the incidence of infection reached a maximum within the pH range of from 5.5 to 6.5, both host and fungus tolerate, and infection occurs within, a much wider pH range. The cardinal temperatures for infection were 5°, 20°, and 30 °C., and there was a close correlation between the temperatures for best growth of the fungus and the host and that for maximum infection. Infection did not occur until the plants were eight weeks old, after which the disease spread until the carrots matured. Initial penetration occurred by hyphal tips forcing their way between the cells of the periderm. Both intercellular and intracellular hyphae were formed abundantly but they did not become established beyond the cambium. Infection bodies began in cells of the periderm where intracellular hyphae accumulated in masses prior to breaking through the outer layer of periderm cells. Two types of histological response to infection were observed: In one a cork layer, formed beneath the infection bodies, resulted in the development of shallow lesions, whereas in the other the infected tissues were broken down and deep lesions were formed in the carrot.