58 results
Utilization of Chlorophyll Fluorescence Imaging Technology to Detect Plant Injury by Herbicides in Sugar Beet and Soybean
- Jonas F. Weber, Christoph Kunz, Gerassimos G. Peteinatos, Hans-Joachim Santel, Roland Gerhards
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- Weed Technology / Volume 31 / Issue 4 / August 2017
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- 20 June 2017, pp. 523-535
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Sensor technologies are expedient tools for precision agriculture, aiming for yield protection while reducing operating costs. A portable sensor based on chlorophyll fluorescence imaging was used in greenhouse experiments to investigate the response of sugar beet and soybean cultivars to the application of herbicides. The sensor measured the maximum quantum efficacy yield in photosystem II (PS-II) (Fv/Fm). In sugar beet, the average Fv/Fm of 9 different cultivars 1 d after treatment of desmedipham plus phenmedipham plus ethofumesate plus lenacil was reduced by 56% compared to the nontreated control. In soybean, the application of metribuzin plus clomazone reduced Fv/Fm by 35% 9 d after application in 7 different cultivars. Sugar beets recovered within few days from herbicide stress while maximum quantum efficacy yield in PS-II of soybean cultivars was reduced up to 28 d. At the end of the experiment, approximately 30 d after treatment, biomass was reduced up to 77% in sugar beet and 92% in soybean. Chlorophyll fluorescence imaging is a useful diagnostic tool to quantify phytotoxicity of herbicides on crop cultivars directly after herbicide application, but does not correlate with biomass reduction.
Does superior caval vein pressure impact head growth in Fontan circulation?
- Tina Trachsel, Christian Balmer, Håkan Wåhlander, Roland Weber, Hitendu Dave, Andrea Poretti, Oliver Kretschmar, Anna Cavigelli-Brunner
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- Cardiology in the Young / Volume 26 / Issue 7 / October 2016
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- 15 January 2016, pp. 1327-1332
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Background
Patients with bidirectional cavopulmonary anastomosis have unphysiologically high superior caval vein pressure as it equals pulmonary artery pressure. Elevated superior caval vein pressure may cause communicating hydrocephalus and macrocephaly. This study analysed whether there exists an association between head circumference and superior caval vein pressure in patients with single ventricle physiology.
MethodsWe carried out a retrospective analysis of infants undergoing Fontan completion at our institution from 2007 to 2013. Superior caval vein pressures were measured during routine catheterisation before bidirectional cavopulmonary anastomosis and Fontan completion as well as head circumference, adjusted to longitudinal age-dependent percentiles.
ResultsWe included 74 infants in our study. Median ages at bidirectional cavopulmonary anastomosis and Fontan were 4.8 (1.6–12) and 27.9 (7–40.6) months, respectively. Head circumference showed significant growth from bidirectional cavopulmonary anastomosis until Fontan completion (7th (0–100th) versus 20th (0–100th) percentile). There was no correlation between superior caval vein pressure and head circumference before Fontan (R2=0.001). Children with lower differences in superior caval vein pressures between pre-bidirectional cavopulmonary anastomosis and pre-Fontan catheterisations showed increased growth of head circumference (R2=0.19).
ConclusionsPatients with moderately elevated superior caval vein pressure associated with single ventricle physiology did not have a tendency to develop macrocephaly. There is no correlation between superior caval vein pressure before Fontan and head circumference, but between bidirectional cavopulmonary anastomosis and Fontan head circumference increases significantly. This may be explained by catch-up growth of head circumference in patients with more favourable haemodynamics and concomitant venous pressures in the lower range. Further studies with focus on high superior caval vein pressures are needed to exclude or prove a correlation.
Foetal echocardiographic assessment of borderline small left ventricles can predict the need for postnatal intervention
- Roland W. Weber, Ricardo Ayala-Arnez, Merna Atiyah, Yousef Etoom, Cedric Manlhiot, Brian W. McCrindle, Edward J. Hickey, Edgar T. Jaeggi, Lynne E. Nield
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- Cardiology in the Young / Volume 23 / Issue 1 / February 2013
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- 05 April 2012, pp. 99-107
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Background
We sought to prospectively determine foetal echocardiographic factors associated with neonatal interventions in borderline hypoplastic left ventricles.
MethodsFoetuses were included who had a left ventricle that was 2–4 standard deviations below normal for length or diameter and had forward flow across the mitral and aortic valves. Factors associated with an intervention in the first month of life or no need for intervention were sought using univariate and multivariate logistic regression models.
ResultsFrom 2005 to 2008, 47 foetuses meeting the criteria had an additional diagnosis (+foetal coarctation/+transverse arch hypoplasia): atrioventricular septal defect 7 (+2/+0), double outlet right ventricle 2 (+0/+0), Shone's complex 19 (+9/+4), and ventricular disproportion 19 (+13/+11; 4 both). There were seven pregnancies terminated, three foetal demises, and five had compassionate care. There were 32 livebirths that either had a biventricular repair (n = 20, n = 2 dead), univentricular palliation (n = 2, both alive), or no intervention (n = 9). Overall survival of livebirths to 6 months of age was 79%. Factors associated with early intervention on first foetal echocardiogram were: obstructed or retrograde arch flow (p = 0.08, odds ratio 3.3), coarctation (p = 0.05, odds ratio 11.4), and left ventricle outflow obstruction (p = 0.05, odds ratio 12.5). Neonatal factors included: Shone's diagnosis (p = 0.02, odds ratio 4.9), bicuspid aortic valve (p = 0.005, odds ratio 11.7), and larger tricuspid valve z-score (p = 0.05, odds ratio 3.6). A neonatal factor associated with no intervention was a larger mitral valve z-score (mean −3.8 versus −4.2 intervention group, p = 0.04, odds ratio 2.8).
DiscussionThe need for early intervention in foetuses with borderline hypoplastic left ventricle can be predicted by foetal echocardiography.
3 - Protozoa: Plasmodiophoromycota
- John Webster, University of Exeter, Roland Weber, Technische Universität Kaiserslautern, Germany
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Summary
Introduction
The Plasmodiophoromycota are a group of obligate (i.e. biotrophic) parasites. The best-known examples attack higher plants, causing economically significant diseases such as club-root of brassicas (Plasmodiophora brassicae), powdery scab of potato (Spongospora subterranea; formerly S. subterranea f. sp. subterranea) and crook-root disease of watercress (S. nasturtii; formerly S. subterranea f. sp. nasturtii). In addition to damaging crops directly, some species (S. subterranea, Polymyxa betae, P. graminis) also act as vectors for important plant viruses (Adams, 1991; Campbell, 1996). Other species infect roots and shoots of non-cultivated plants, especially aquatic plants. Algae, diatoms and Oomycota are also attacked. If the nine species of Haptoglossa, which parasitize nematodes and rotifers, are included in the Plasmodiophoromycota, the phylum currently comprises 12 genera and 51 species (Dick, 2001a). Genera are separated from each other largely by the arrangement of resting spores in the host cell (Waterhouse, 1973). This feature has also been used for naming most genera; for instance, in Polymyxa, numerous resting spores are contained within each sorus, whereas in Spongospora the resting spores are grouped loosely in a sponge-like sorus (Fig. 3.6). Accounts of the Plasmodiophoromycota have been given by Sparrow (1960), Karling (1968), Dylewski (1990) and Braselton (1995, 2001).
Taxonomic considerations
Plasmodiophoromycota have traditionally been studied by mycologists and plant pathologists. Many general features of their biology and epidemiology are similar to those of certain members of the Chytridiomycota such as Olpidium (see p. 145).
25 - Anamorphic fungi (nematophagous and aquatic forms)
- John Webster, University of Exeter, Roland Weber, Technische Universität Kaiserslautern, Germany
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Summary
Throughout this book we have attempted to consider fungi showing predominantly or purely asexual reproduction together with their known or suspected teleomorphs. However, certain groups of taxonomically diverse fungi colonizing the same specialized habitats or substrates are best understood in their ecological context, especially if they show strikingly similar adaptations and morphology despite their different evolutionary histories. Two cases illustrating such convergent evolution among anamorphic fungi are the nematophagous habit and the aquatic habitat, which we shall consider in turn in this chapter.
Nematophagous fungi
Nematodes are a very varied group of invertebrates. They are particularly common as free-living saprotrophic species in the soil, around plant roots, on dung and in all kinds of decomposing plant matter, as well as in freshwater and marine habitats. Most saprotrophic nematodes feed on bacteria, although fungal hyphae may also be consumed. Other species parasitize animals, releasing their eggs or motile stages into the environment when their hosts defaecate. Plant-parasitic species chiefly attack roots as free-living or sedentary organisms. Sedentary species form adult stages inside plant root tissues where they cause the economically important root knot diseases (Meloidogyne spp.) or root cyst diseases (Heterodera spp. and Globodera spp.). Plant-parasitic nematodes are readily recognized because their mouth parts are modified as stylets with which they penetrate plant tissues. Gravid females of cyst nematodes enlarge, and their bodies become converted into a hardened cyst containing the eggs.
21 - Heterobasidiomycetes
- John Webster, University of Exeter, Roland Weber, Technische Universität Kaiserslautern, Germany
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Summary
Introduction
The class Heterobasidiomycetes is approximately synonymous with the terms ‘Phragmobasidiomycetes’ or ‘jelly fungi’ and contains fungi with the following characteristics.
1. The dolipore septum is complex, i.e. it is surrounded by a parenthesome. Parenthesomes are also found in the Homobasidiomycetes (Chapters 19 and 20), but not in the Urediniomycetes (Chapter 22) and Ustilaginomycetes (Chapter 23).
2. The basidia of Heterobasidiomycetes may be strongly lobed and often divided by transverse, oblique or longitudinal septa. Such basidia are loosely termed heterobasidia, especially if they arise directly from hyphae instead of teliospores as in most Urediniomycetes and Ustilaginomycetes. If the basidia are septate, they are also called phragmobasidia. The sterigma of the heterobasidium is unusually prominent and is often termed epibasidium (Martin, 1945). In contrast, the basidia of Homobasidiomycetes are club-shaped and always single-celled.
3. The fruit bodies of most Heterobasidiomycetes are simpler in architecture than those of Homobasidiomycetes, and the hymenium is not normally protected by a roof- or shelf-like architecture. In compensation, these simple fruit bodies are generally able to survive drying and rehydration, with fresh crops of basidiospores produced after each rehydration event. Fully hydrated basidiocarps are typically greatly swollen and gelatinous, hence the term ‘jelly fungi’ for the Heterobasidiomycetes.
4. The basidiospores of most species are capable of producing secondary spores which may be ballistoconidia, passively released conidia or yeast cells.
Species included in this class show considerable morphological diversity, and taxonomic concepts have been in a state of flux.
10 - Hemiascomycetes
- John Webster, University of Exeter, Roland Weber, Technische Universität Kaiserslautern, Germany
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Summary
Introduction
The class Hemiascomycetes contains the classical ascomycete yeasts, exclusive of those which belong to the Archiascomycetes (see the preceding chapter) and the ‘black yeasts’ such as Aureobasidium (see p. 486). Detailed descriptions of the individual yeast genera and species are given in Kurtzman and Fell (1998) and Barnett et al. (2000). A useful taxonomic overview is that by Kurtzman and Sugiyama (2001). There is only one order, the Saccharomycetales, which has been divided into 11 families and 276 species (Kirk et al., 2001; Kurtzman & Sugiyama, 2001). However, detailed phylogenetic analyses of the Hemiascomycetes (Kurtzman & Robnett, 1998, 2003) indicate that this family arrangement is likely to be modified in the future, and for this reason we shall focus on selected genera.
The key feature that distinguishes the Hemi- and Archiascomycetes from the higher ascomycetes (Euascomycetes) is that ascogenous hyphae and an ascocarp, i.e. an investment of sterile hyphae surrounding the asci, are lacking in the first two groups. Instead, the asci are formed freely and singly, either directly following karyogamy or more rarely after a prolonged diploid phase. Another distinguishing feature is the composition of the cell wall, which contains very little chitin in the Hemi- and Archiascomycetes. Chitin is often confined to a small ring around the site where the daughter cell is produced (the bud scar). An ultrastructural feature of distinction concerns the septal pore of any hypha that may be produced.
2 - Protozoa: Myxomycota (slime moulds)
- John Webster, University of Exeter, Roland Weber, Technische Universität Kaiserslautern, Germany
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Summary
Introduction
When the first slime moulds were described by Johann H. F. Link in 1833, they were given the term myxomycetes (Gr. myxa = slime). Link used the suffix -mycetes because of the superficial similarity of the fructifications of slime moulds with the fruit bodies of certain fungi, notably Gasteromycetes (see Chapter 20). Although it has been appreciated for some time that they lack any true relationship with the Eumycota (de Bary, 1887; Whittaker, 1969), slime moulds have none the less been studied mainly by mycologists rather than protozoologists, probably because they occur in the same habitats as fungi and are routinely encountered during fungus forays. Since slime moulds are only rarely covered by zoology courses even today, they are briefly described in this chapter, referring to more specialized literature as appropriate.
Slime moulds differ substantially from the Eumycota not only in phylogenetic terms, but also regarding their physiology and ecology. Their vegetative state is that of individual amoebae in the cellular slime moulds, or of a multinuclear (coenocytic) plasmodium in the plasmodial slime moulds. Motile stages bearing usually two anterior whiplash-type flagella may be present in the plasmodial slime moulds (Sections 2.4, 2.5) and in the Plasmodiophoromycota (Chapter 3). Amoebae or plasmodia feed by the ingestion (phagocytosis) of bacteria, yeast cells or other amoebae. This is followed by intracellular digestion in vacuoles. The mode of nutrition in slime moulds is therefore fundamentally different from extracellular degradation and absorption as shown by Eumycota.
6 - Chytridiomycota
- John Webster, University of Exeter, Roland Weber, Technische Universität Kaiserslautern, Germany
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Summary
Introduction
The phylum Chytridiomycota comprises over 900 species in five orders (D. J. S. Barr, 2001; Kirk et al., 2001). Fungi included here are colloquially called ‘chytrids’. Most chytrids grow aerobically in soil, mud or water and reproduce by zoospores with a single posterior flagellum of the whiplash type, although the zoospores of some members of the Neocallimastigales are multiflagellate. Some species inhabit estuaries and others the sea. Sparrow (1960) has given an extensive account of aquatic forms, Karling (1977) a compendium of illustrations, and Powell (1993) has provided examples of the importance of the group. Many members are saprotrophs, utilizing cellulose, chitin, keratin, etc., from decaying plant and animal debris in soil and mud, whilst species of Caulochytrium grow as mycoparasites on the mycelium and conidia of terrestrial fungi (Voos, 1969). Saprotrophs can be obtained in crude culture by floating baits such as cellophane, hair, shrimp exoskeleton, boiled grass leaves and pollen on the surface of water overlying samples of soil, mud or pieces of aquatic plant material (Sparrow, 1960; Stevens, 1974; Willoughby, 2001). From such crude material, pure cultures may be prepared by streaking or pipetting zoospores onto agar containing suitable nutrients and antibiotics to limit contamination from bacteria. The growth and appearance of chytrids in pure culture is variable and often differs significantly from their natural habit. This has led to problems in classification systems based on thallus morphology (Barr, 1990, 2001). The availability of cultures has, however, facilitated studies on chytrid nutrition and physiology (Gleason, 1976).
16 - Lichenized fungi (chiefly Hymenoascomycetes: Lecanorales)
- John Webster, University of Exeter, Roland Weber, Technische Universität Kaiserslautern, Germany
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Introduction
The dual nature of lichens was first hinted at by de Bary (1866) and clearly recognized by Schwendener (1867). A lichen is now defined as a ‘self-supporting association of a fungus (mycobiont) and a green alga or cyanobacterium (photobiont)’ (Kirk et al., 2001), ‘resulting in a stable thallus of specific structure’ (Ahmadjian, 1993). The fungal partner usually contributes most of the biomass to this symbiosis, including the external surface. It is thus termed the exhabitant, whereas the unicellular or filamentous photobiont cells are collectively called the inhabitant because they are located inside the lichen thallus (see Ahmadjian, 1993). Most lichens have a characteristic appearance which permits their identification if suitable keys are available (e.g. Purvis et al., 1992; Wirth, 1995a, b; Brodo et al., 2001). Since the structure of lichens is almost entirely due to the fungal partner, lichen taxonomy is synonymous with the taxonomy of the mycobiont.
It is possible to grow the algal and fungal partners of many lichens separately in pure culture (Ahmadjian, 1993; Crittenden et al., 1995). Whereas most photobionts multiply readily in pure culture, the fungal partner, if it grows at all, typically shows slow growth as a sterile leathery mycelium but does not produce the characteristic lichen thallus. This is in marked contrast to the natural thallus where the mycobiont displays its full sexual and asexual cycle, whereas the photobiont cells often appear swollen and are arrested in their cell cycle, i.e. their cell division is controlled by the mycobiont.
Frontmatter
- John Webster, University of Exeter, Roland Weber, Technische Universität Kaiserslautern, Germany
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4 - Straminipila: minor fungal phyla
- John Webster, University of Exeter, Roland Weber, Technische Universität Kaiserslautern, Germany
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Summary
Introduction
The kingdom Chromista was erected by Cavalier-Smith (1981, 1986) to accommodate eukaryotic organisms which are distinguishable from the Protozoa by a combination of characters. Some of these are concerned with details of photosynthesis, such as the enclosure of chloroplasts in sheets of endoplasmic reticulum, and the absence of chlorophyll b, the latter feature being used for the naming of the kingdom. Other defining characters apply also to the non-photosynthetic members of the Chromista (Kirk et al., 2001). These are as follows:
1. The structural cell wall polymer is cellulose, in contrast to walls of Eumycota which contain chitin.
2. The inner mitochondrial membrane is folded into tubular cristae (Fig. 4.1a) which are also found in plants. In contrast, mitochondrial cristae are generally lamellate in the kingdoms Eumycota (Fig. 4.1b) and Animalia.
3. Golgi stacks (dictyosomes) are present; these are also found in the Protozoa (see p. 64). In contrast, in the Eumycota the Golgi apparatus is usually reduced to single cisternae (see Figs. 1.3, 1.10).
4. Flagella are usually present during particular stages of the life cycle; they always include one straminipilous flagellum (Lat. stramen = straw, pilus = hair). Dick (2001a) considered this feature to be of such high phylogenetic significance that he has renamed the kingdom Chromista as Straminipila. The straminipilous flagellum is discussed in detail in the following section.
5. The amino acid lysine is synthesized via the α,ε-diaminopimelic acid (DAP) pathway.
References
- John Webster, University of Exeter, Roland Weber, Technische Universität Kaiserslautern, Germany
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Preface to the first edition
- John Webster, University of Exeter, Roland Weber, Technische Universität Kaiserslautern, Germany
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Summary
There are several available good textbooks of mycology, and some justification is needed for publishing another. I have long been convinced that the best way to teach mycology, and indeed all biology, is to make use, wherever possible, of living material. Fortunately with fungi, provided one chooses the right time of the year, a wealth of material is readily available. Also by use of cultures and by infecting material of plant pathogens in the glasshouse or by maintaining pathological plots in the garden, it is possible to produce material at almost any time. I have therefore tried to write an introduction to fungi which are easily available in the living state, and have tried to give some indication of where they can be obtained. In this way I hope to encourage students to go into the field and look for fungi themselves. The best way to begin is to go with an expert, or to attend a Fungus Foray such as those organized in the spring and autumn by mycological and biological societies. I owe much of my own mycological education to such friendly gatherings. A second aim has been to produce original illustrations of the kind that a student could make for himself from simple preparations of living material, and to illustrate things which he can verify for himself. For this reason I have chosen not to use electron micrographs, but to make drawings based on them.
23 - Ustilaginomycetes: smut fungi and their allies
- John Webster, University of Exeter, Roland Weber, Technische Universität Kaiserslautern, Germany
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Ustilaginomycetes
The Ustilaginomycetes are one of the four main classes of Basidiomycota and contain about 1500 species (Kirk et al., 2001). In its present form as circumscribed by Begerow et al. (1997) and Bauer et al. (1997, 2001), this group is monophyletic. Hypha-producing Ustilaginomycetes are united by their lifestyle as ecologically obligate plant pathogens, often with an additional free-living (saprotrophic) yeast phase. They can be distinguished from the rust fungi in that haustoria are either altogether absent or, where present, take the shape of simple intracellular hyphae or hyphal extensions which invaginate the host plasmalemma but are not differentiated into a narrow neck and a wider haustorial body. Further, intracellular hyphae of Ustilaginomycetes usually secrete a thick sheath which is readily visible by transmission electron microscopy (see Figs. 23.6 and 23.17). The septa either lack perforations or contain simple pores or dolipores which are similar to those in the Urediniomycetes in lacking parenthesomes. True clamp connections are not usually found. The basidia of smut fungi produce numerous basidiospores whereas those of rust fungi usually produce only four.
The class Ustilaginomycetes has been divided into three subclasses by Begerow et al. (1997, 2000). We shall consider representatives of two of these. The Ustilaginomycetidae (Section 23.2) are the most important plant-pathogenic Ustilaginomycetes, causing smut-like symptoms. Typical members of the Exobasidiomycetidae (Section 23.4) cause other biotrophic diseases and are distinguished from the former by producing basidia directly from parasitic mycelium, not from teliospores.
Plate section
- John Webster, University of Exeter, Roland Weber, Technische Universität Kaiserslautern, Germany
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Introduction to Fungi
- 3rd edition
- John Webster, Roland Weber
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This new edition of the universally acclaimed and widely-used textbook on fungal biology has been completely re-written, drawing directly on the authors' research and teaching experience. The text takes account of the rapid and exciting progress that has been made in the taxonomy, cell and molecular biology, biochemistry, pathology and ecology of the fungi. Features of taxonomic relevance are integrated with natural functions, including their relevance to human affairs. Special emphasis is placed on the biology and control of human and plant pathogens, providing a vital link between fundamental and applied mycology. The book is richly illustrated throughout with specially prepared drawings and photographs, based on living material. Illustrated life-cycles are provided, and technical terms are clearly explained. Extensive reference is made to recent literature and developments, and the emphasis throughout is on whole-organism biology from an integrated, multidisciplinary perspective.
12 - Hymenoascomycetes: Pyrenomycetes
- John Webster, University of Exeter, Roland Weber, Technische Universität Kaiserslautern, Germany
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Introduction
The Pyrenomycetes are defined here according to Samuels and Blackwell (2001) as fungi which produce non-fissitunicate or occasionally prototunicate asci usually in flask-shaped ascomata (perithecia), less frequently in cleistothecia. The sub-class Pyrenomycetes is one of several groups belonging to the huge and heterogeneous class Hymenoascomycetes. The characteristic feature of this class is that the asci develop in an ascohymenial way, i.e. the ascoma is formed after plasmogamy and the pairing of nuclei have occurred, and the asci therefore arise from a hymenium. This is in contrast to asci being formed singly (Archiascomycetes, Hemiascomycetes), scattered throughout the fruit body (Plectomycetes), or formed in a locule within a pre-formed fruit body (Loculoascomycetes). Although the term ‘Pyrenomycetes’ is not generally understood in a taxonomic sense at the present, Samuels and Blackwell (2001) pointed out the monophyly of a core group of orders, including all those which we shall describe in this chapter (summarized in Table 12.1).
The development of the perithecium follows several different schemes defined by Luttrell (1951), which are described in more detail for the different orders. Following fertilization and plasmogamy, the ascogonium gives rise to ascogenous hyphae while the perithecial wall is formed by hyphae arising from the ascogonial stalk or elsewhere. Sterile hyphae growing up from the basal fertile region (paraphyses) and periphyses which line the inner surface of the ostiole, may be present. The development of the opening of the perithecium is typically schizogenous, i.e.
Acknowledgements
- John Webster, University of Exeter, Roland Weber, Technische Universität Kaiserslautern, Germany
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7 - Zygomycota
- John Webster, University of Exeter, Roland Weber, Technische Universität Kaiserslautern, Germany
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Summary
Introduction
The phylum Zygomycota comprises the first group of fungi considered in this book which lacks any motile stage. Asexual reproduction is by spores which are called aplanospores because they are non-motile, and sporangiospores because they are typically contained within sporangia. They are dispersed passively by wind, insects and rain splash, although violent liberation of entire sporangia (e.g. Pilobolus) or individual spores (e.g. Basidiobolus, Entomophthora) can also occur. Sexual reproduction is by gametangial copulation which is typically isogamous and results in the formation of a zygospore. The mycelial organization is coenocytic, and the cell wall contains chitin and its deacetylated derivative, chitosan (Bartnicki-Garcia, 1968, 1987; see Fig. 1.5). As in the Chytridio-, Asco- and Basidiomycota, the mitochondria possess lamellate cristae, and the Golgi system is reduced to single cisternae. Lysine is synthesized by the α-aminoadipic acid (AAA) route, as it appears to be in all Eumycota.
General accounts of the Zygomycota have been given by Benjamin (1979), Benny (2001) and Benny et al. (2001). Molecular evidence indicates that the group may have diverged from the Chytridiomycota early in the history of terrestrial life. The Zygomycota, in turn, probably gave rise to the Asco- and Basidiomycota, i.e. the ‘higher fungi’ (Jensen et al., 1998; Schüssler et al., 2001). Two classes are included in the Zygomycota, namely Zygomycetes comprising 870 species in 10 orders, and Trichomycetes with 218 species in 3 orders (Kirk et al., 2001). The most prominent orders of the Zygomycetes are the Mucorales, Entomophthorales and Glomales.