CHAPTER 2 Crop losses and their causes
2.1Types of crop losses..............................................................R.P. Jaques and W.R. Jarvis
Production losses
Post-harvest losses
2.2Causes of crop losses............................................................R.P. Jaques and W.R. Jarvis 2.3Pathogens and other pests - Identification....................................................W.L Seaman
Bacteria and actinomycetes ................................................W.R. Jarvis and R.J. Howard Fungi...............................................................................................................W.R. Jarvis Viruses and viroids.........................................................................................W.R. Jarvis Virus-like pathogens (wall-less prokaryotes)..................................................W.R. Jarvis Nematodes..............................................................................T.C. Vrain and B.A. Ebsary Insects..................................................................................R.P. Jaques and J.A. Garland Mites and spiders..............................................................J.A. Garland and W.L Seaman Centipedes and millipedes.............................................................................J.A. Garland Symphylans......................................................................J.A. Garland and W.L. Seaman Slugs and snails................................................................J.A. Garland and W.L. Seaman Sow bugs and pillbugs.....................................................J.A. Garland and W.L. Seaman Parasitic higher plants....................................................................................R.J. Howard 2.4Climate and environment......................................................R.P. Jaques and W.R. Jarvis
Pest distribution..............................................................................................W.R. Jarvis Environment-related disorders........................................................................W.R. Jarvis Chemical injury...............................................................................................W.R. Jarvis Nutritional disorders.......................................................................................W.R. Jarvis Additional references
Tables
2.3a Host ranges of economically important nematode pests on vegetable crops in Canada 2.3b Characteristics of major groups of insects associated with vegetable crops in Canada
2.3c Key to the principal orders of insects associated with vegetable crops in Canada
2.3d Weeds commonly occurring in vegetable crops in Canada
2.1 Types of crop losses
Production losses - Diseases, insects, weeds and other pests annually cause substantial losses in the yield and quality of vegetables produced in Canada. Reliable estimates of these losses are not available, but they probably are proportional to losses in the USA. Even with the extensive application of pesticides, the estimated reductions in the farm-gate value of selected vegetable crops in the United States caused by diseases range from 8 to 23%, by insects 4 to 21 %, and by weeds 8 to 13%. If it is accepted that the average losses caused by diseases, insects and weeds in Canada are 15.5, 12.5 and 10.5%, respectively, they would have reduced returns to the vegetable industry by $172.7, $138.2 and $115.2 million, respectively, in 1990. If the costs of crop protection practices were factored in, these figures would be even higher. In the United States in 1987, crop losses caused by diseases and insects in specific vegetables were, respectively: cole crops 9 and 13%, lettuce 12 and 7%, potato 20 and 6%, tomato 21 and 7%, sweet corn 8 and
19%, onion 21 and 4%, cucumber 15 and 21%, pea 23 and 4%, and pepper 14 and 7%. Losses in greenhouse lettuce, cucumber and tomato are similar, but pest damage may necessitate replanting the whole crop. Until resistant cultivars of tomato became available, this was regularly the case with fusarium crown and root rot.
Post-harvest losses - Reduced yield and quality from pest damage in the field may be equalled or exceeded by losses in storage. This is especially the case where freshly harvested produce is not rapidly cooled or where it is not transported and stored under controlled conditions. For example, it is not unusual to see truckloads of perishable vegetables parked on farms, at roadside truck-stops and at food terminals rapidly deteriorating in the full summer sun. Similarly, attempts to dry onions in primitive storages with humid air frequently result in wetter, not drier, onions in production areas of the Great Lakes region. Such crops are often destroyed by diseases, such as neck rot and sour skin. Poorly stored carrot, potato and cabbage crops also are subject to substantial losses.
Selected references
Kim, S.H., L.B. Forer, and J.L. Longnecker. 1975. Recovery of plant pathogens from commercial peat-products. Proc. Am. Phytopathol. Soc. 2:124.
Pimentel, D., L. McLaughlin, A. Zepp, B. Lakitan, T. Kraus, P. Kleinman, F. Vancini, W.J.
Roach, E. Graap, W.S. Keeton, and G. Selig. 1991. Environmental and economic impacts of reducing U.S. agricultural pesticide use. Pages 679–720 in D. Pimentel, ed., Handbook of Pest Management in Agriculture. Vol. 2. CRC Press, Boca Raton, Florida. 773 pp.
2.2 Causes of crop losses
Direct crop losses caused by diseases and pests may be measured as the proportion of crop not sold. In addition to losses in yield and quality in the field and later during storage and transport, there are many, less tangible ways in which diseases and pests exact an economic toll. For example, the fungus Botrytis cinerea may cause multiple but almost imperceptible ghost spot lesions on tomato fruit, which, depending on the rigor of official or consumer inspection, may result in little or no financial loss to the grower. However, the same fungus causing a single, girdling lesion on the stem of an indeterminate tomato cultivar will result in the total loss in yield from that plant, as often happens in the greenhouse.
Bacterial spot on processing tomatoes makes the skin very difficult to peel by standard factory procedures, so the skins have to be removed by hand, which is very expensive. On the other hand, buyers of fresh-market tomatoes at roadside stands may scarcely notice a few lesions of bacterial spot. Similarly, when cabbage is fermented to produce sauerkraut, or cooked, the lesions caused by thrips are very pronounced and unacceptable, whereas thrips damage may be of little consequence if the cabbage is finely chopped and used fresh in coleslaw.
Nematode damage to roots may be mechanical or chemical, thereby reducing root capacity to absorb and translocate water and nutrients, even when soil moisture is adequate. Some vegetable crops are tolerant of nematode damage, while others are highly sensitive. Seedlings and young transplants usually are especially susceptible. The distribution of nematodes in the soil, whether in the field or in the greenhouse, normally is uneven. Plant-parasitic nematodes may reduce crop yield and quality but other biotic and abiotic stresses on plants make it difficult to predict the impact of nematode damage. Losses may increase significantly if nematodes interact with other
pathogens, such as fungi and viruses. In Canada, yield-loss data, where available, are generally restricted to a few crops within a limited geographical area.
Insects and mites may damage vegetable plants directly or indirectly. For example, larvae and adults of the Colorado potato beetle may extensively defoliate a potato plant, substantially reducing its photosynthetic capacity and resulting in significant reduction in yield of tubers or even death of the plant; however, infestations that occur late in the growing season may have little effect on yield. Direct damage also may be caused by wireworms that feed or burrow into tubers, and this damage may be augmented by rot caused by bacteria and fungi. Aphids and leafhoppers suck on the foliage of the plant, reducing its vigor, but these insects also may damage a crop indirectly by transmitting plant viruses. Reduction in the yield of greenhouse-grown tomato, resulting from extensive (piercing and sucking) feeding by adults and nymphs of the greenhouse whitefly and the two-spotted spider mite, is a less direct form of damage to the crop than is the feeding on the fruit of field grown tomato by horn worms and cutworms. Consumption of foliage of cabbage plants by larvae of the cabbage looper or the imported cabbage worm reduces the vigor of the plant, resulting in a smaller head; these insects also may feed directly in the head, rendering it unmarketable, or on the outer wrapper leaves of fresh-market cabbage and cauliflower, downgrading marketability. Similarly, the presence of insects in a marketed product, such as heads of broccoli, may render the product unmarketable without visible evidence of feeding by the insect.
The economic significance of damage and the action threshold applied in deciding on measures to manage populations of pests depend on the severity of damage, the value of the crop, and the proposed end use of the crop. For example, the threshold approaches zero for species that cause damage directly to the part of the crop to be used by the consumer; these include the carrot rust fly in carrot and the corn borer in pepper and sweet corn. On the other hand, low populations of pests that cause foliar damage but do not feed on or damage marketable parts of the plant may be tolerated, and thus the action threshold for implementation of control procedures is higher; examples include the Colorado potato beetle on potato and the cabbage maggot on cabbage. Similarly, relatively high numbers of the two-spotted spider mite and of the greenhouse whitefly can be tolerated on greenhouse-grown cucumber and tomato without affecting the yield of marketed product significantly. Action thresholds also may vary with the stage of development of the vegetable plant when attacked. For example, low populations of the imported cabbageworm and cabbage looper can be tolerated when they feed on the foliage of young plants of cabbage, cauliflower and Brussels sprouts. Later, however, the tolerance for these pests is greatly reduced when they feed on the head or wrapper leaves of cabbage or cauliflower or in the head of broccoli. Likewise, thresholds for pests that cause indirect damage is very low if the pest can disseminate plant pathogens. For example, low populations of aphids do not cause significant loss of yield in potato, but the potential for spread of aphid-vectored viruses is so high that control measures must be considered whenever aphids appear, particularly in seed-potato crops.
Crop losses caused by competition from weeds can be assessed quite readily, but weeds also contribute to overall crop losses by acting as alternative hosts for pathogens and insects. For example, wild cucumber (Echinocystis lobata (Michx.) Torr. & Gray) harbors the fungus Didymella bryoniae, which causes gummy stem blight in melon and cucumber (see Greenhouse cucumber, 22.11). The universal pathogens Botrytis cinerea, Sclerotinia sclerotiorum and
S.minor are found on many weed species, B. cinerea in particular having hundreds of hosts.
Weeds also may act as a reservoir for many vegetable viruses and mycoplasma-like
organisms, and of their insect and nematode vectors. The passage of workers and machinery through weed-infested crops can transmit viruses from weeds to crop plants; weed canopies provide the humid and cool microclimate in which fungi and bacteria infect their vegetable hosts; and finally, weeds provide shelter for pest insects and other types of animals, such as rabbits and rodents. Weed control, therefore, is an important part of a pest management program for vegetable crops.
2.3 Pathogens and other pests
Identification Correctly identifying both the host plant and the causal agent of a disease or pest damage will enable a vegetable grower to choose effective management practices that will prevent further damage to crop plants without affecting harmless or beneficial organisms. In the crop chapters of this book, the scientific or Latin names of pathogenic microorganisms and pests follow their common names; the italicized scientific name usually is followed by the name (often abbreviated) of the scientist(s) who described and named the organism. Using the scientific name for organisms avoids confusion over differences in language and in the selection of common names. For example, in some regions of Canada, the rutabaga is known as a swede or even as a winter turnip, but it is universally recognized by its scientific name Brassica napus var. napobrassica (L.) Reichb. The recommended common and scientific names of the major and minor vegetable crops grown in Canada are listed in Table 1.3. Classifying and naming plants and animals, including insects and microorganisms, follows a system of binomial nomenclature that is based chiefly on characteristics of vegetative and reproductive structures. Within species, populations also may be described at the functional or molecular level. Characteristics of the chief groups of organisms causing injury and disease in plants are described briefly in this chapter. More detailed descriptions of causal organisms are included in the discussion of specific disease and pest problems in the crops chapters.
Bacteria and actinomycetes
Bacteria are tiny, one-celled microorganisms (prokaryotes) that, like fungi, require an external food supply for their energy. They, too, are facultative parasites of plants and are capable also of independent existence in plant residues, water or soil. Bacteria differ in certain fundamental ways from fungi in their cell structure, but they have very few morphological features that distinguish them from one another. Thus, a diagnostician has to rely on laboratory tests to identify them. Bacteria gain entry into plants through the stomata or through wounds caused by abrasion, insects or pruning. Bacterial diseases are highly infectious and are particularly difficult to control. Bacteria are spread easily by splashing water, particularly wind-blown rain and overhead irrigation. Some bacteria are carried from plant to plant by insect vectors, and they are all spread by hands, machinery and tools. Many also are carried on or in seed. Some pathogenic bacteria are capable of infecting one or a few host species or cultivars, whereas others, such as Erwinia carotovora subsp. carotovora, a soft-rotting bacterium, have a very wide host range.
Actinomycetes are classified with bacteria because nuclear fusion does not occur and they have cell wall biochemical characteristics more closely resembling those of bacteria than of fungi. They do resemble fungi in their filamentous morphology, but differ notably in the small
diameter (usually about 1 :m) of their vegetative filaments. The most important actinomycete pathogen of vegetables is Streptomyces scabies, the cause of scab on such crops as potato, radish, carrot, rutabaga, parsnip and beet.
Fungi[The classification of several sections within this group of pathogens has changed substantially since the book was written, but details of reproduction are unchanged]
Fungi are microscopic plants with a basic, threadlike structure collectively called the mycelium. They have no chlorophyll and thus are unable to utilize carbon dioxide from the air for their nutrition. Instead, they utilize previously formed carbon compounds as a source of energy. They obtain these materials while growing saprophytically on the products or remains of plants and animals, or by parasitizing living plants and animals. In living, green plants, fungi usually degrade the host, producing visible damage, which, in vegetable crops, causes losses in yield and quality. As saprophytes, fungi are responsible for much of the natural breakdown of organic material and hence the recycling of essential elements and compounds in the environment. Mushrooms and toadstools are larger fungi that can be saprophytic, parasitic or, in many cases, symbiotic with green plants (mycorrhiza), living in plant roots to the mutual benefit of both fungus and host.
Parasitic fungi fall into two broad groups: obligate parasites, which depend entirely on a living host for their nutrition and reproduction, and facultative parasites, which can do considerable damage to crop plants as parasites, but can also live indefinitely as saprophytes on plant remains. Obligate plant parasites include the rusts, powdery mildews and downy mildews, whose names broadly describe the symptoms of the diseases they cause. The ubiquitous gray mold fungus Botrytis cinerea is a facultative parasite. Virtually all fungi that cause plant diseases form microscopic spores that serve two basic functions: to act as dispersal and infective propagules to spread the disease, and to act as resistant structures permitting the pathogen to survive adverse environmental conditions. In addition, many fungi also form compact, hard structures called sclerotia. These, like spores, are capable of resuming growth under favorable conditions to infect the host plant, sometimes after months or years.
Spores are dispersed in various ways, for example by air, in water through the soil or irrigation systems, by insects, or on hands, clothing and tools. Spores are the principal agents of plant infection. They germinate under suitable conditions, almost invariably in a water droplet or film or on a moist wound, to form a thread-like germ tube that can penetrate through the plant epidermis directly or through a stomatal pore. Once inside the plant tissue, the mycelium permeates the host tissues, sometimes blocking the water-conducting system, as in the wilt diseases. As the food supply for the fungus diminishes, more spores are formed to spread the pathogen through the crop. By this time the host is either severely damaged or dead.
Spores can be produced by a sexual process, which imparts genetic variability to the fungus and can give rise to pesticide resistance or overcome host resistance, or they can be produced in huge numbers by an asexual, vegetative process. Some fungi form two or more types of spores that often do not much resemble each other in the same fungus. The sexual state is called the teleomorph and gives the fungus its proper, scientific (Latin) name, while asexual states are called anamorphs and frequently have a different Latin name. For example, the gray mold fungus Botryotinia fuckeliana is the teleomorph name for a rare, tiny, toadstool-like fungus. However, it is better known as Botrytis cinerea, the name that describes its asexual, dispersive
and infective spores (conidia), which are arranged in a grape-like cluster. Botrytis cinerea is derived from the Greek, meaning an ashy-colored bunch of grapes. The fungus also has anamorphic microconidia, which are not infectious but have a sexual function, and chlamydospores. The latter are durable, long-lived spores in nature.
Viruses and viroids
Viruses are submicroscopic particles consisting of a nucleic acid, either ribose nucleic acid (RNA) or deoxyribose nucleic acid (DNA). They multiply by inducing host cells to form more virus particles at the expense of host metabolism. The nucleic acid can be single- or double-stranded. Virus particles are rod-like, straight or flexuous, bacillus-like (rhabdoviruses), or isometric (polyhedral). Some small viruses are dependent on another virus for multiplication; these are called satellite viruses and require a helper virus for infection. Gemini viruses are paired, isometric particles with single-stranded RNA; an example is maize streak virus. Viroids are small units of single-stranded RNA arranged in a circle, devoid of protein, yet still capable of causing plant diseases; potato spindle tuber is a notable example.
The criteria for identifying and classifying a virus depends on certain physical, chemical and biological properties, including whether the nucleic acid is DNA or RNA, whether it is single- or double-stranded, and whether it has a membrane around the protein coat. In practical terms, indicator plants, often tobacco or Chenopodium species, are inoculated with sap from a diseased plant, and they produce symptoms characteristic of a particular virus. Since viruses have a protein coat, specific antibodies can be induced in animal serum, which can be made to react chemically and specifically in various diagnostic tests, such as precipitin or enzyme-linked immunosorbent assay (ELISA) tests.
Most viruses can be transmitted from plant to plant by infected sap introduced by injury, on hands, machinery or clothing, or by grafting. Many viruses are transmitted by insects, especially aphids; others are transmitted by mites, nematodes, fungi, or the parasitic plant dodder (Cuscuta spp.). Some viruses are seed- and pollen-borne.
Virus-like pathogens (wall-less prokaryotes)[The classification of this group of pathogens has changed substantially since the book was written]
Lying somewhere between viruses and bacteria in characteristics are a group of microorganisms known as wall-less prokaryotes; in the crops sections of this book they are referred to as virus-like pathogens. They have genetic material but no nucleus or cytoplasmic organelles, in contrast to the more complex eukaryotes that include the fungi. Bacteria are also prokaryotes, but they have a cell wall. Wall-less prokaryotes have been linked with some 200 plant diseases. There are three main groups that cause plant diseases, 1) mycoplasma-like organisms (MLOs) of indefinite form that are more or less restricted to sieve tubes of plant vascular systems; 2) spiroplasma-like organisms, which are helical in form and restricted to sieve tubes; and 3) rickettsia-like organisms that resemble in form the typhus-causing Rickettsia, which has a rippled, trilaminate outer membrane. MLOs cause yellows diseases, (e.g. aster yellows) of lettuce, celery, potato, carrot and about 180 other plants, as well as leaf mottling, flower virescence, dwarfing and witches'-brooms. Typically, MLOs are transmitted from plant to plant by leafhoppers and can be
controlled by the antibiotic tetracycline. Spiroplasmas cause such vegetable diseases as corn stunt.
Nematodes
Plant parasitic nematodes or eel worms are small (usually less than 1 mm long), worm-like animals that live in soil. They are broadly divided into two groups: ectoparasitic nematodes that attack the plant externally, and endoparasitic nematodes that live, at least for part of their life cycle, inside the host tissues. All parasitic nematodes have mouth spears through which saliva is injected into the host tissues; it is the saliva that induces most of the damage in plants, for example tissue necrosis or the proliferation of giant cells, which can produce galls. Some nematodes, while causing little direct damage to plants, transmit viruses; such nematodes include species of Xiphinema, Longidorus and Trichodorus.
Worldwide, several hundred nematode species are plant parasites, most of which live in the soil. Many thousands of other species are free-living in the soil, feeding on fungi, bacteria and other microbes. Others are associated with animals, including man; some are naturally occurring biocontrol agents of insects. Most plant-parasitic nematodes feed on a relatively narrow spectrum of hosts, and only a few species are considered agricultural pests. Canada has relatively few nematodes that are of major economic importance in field and greenhouse vegetable crops (see Table 2.3a), mainly because of unfavorable climatic conditions.
Endoparasitic nematodes - These nematodes usually penetrate the roots, and feed and multiply within root tissues; some also invade bulbs, leaves and stems. They include the northern root-knot nematode Meloidogyne hapla Chitwood, which attacks almost all types of vegetable crops commonly grown in gardens, fields and greenhouses in Canada (see Carrot, 6.20). The southern rootknot nematodes Meloidogyne incognita (Kofoid & White) Chitwood, M. javanica (Treub) Chitwood, and M. arenaria (Neal) Chitwood do not occur in the field in Canada, but they can persist in greenhouses when imported from warmer climates. The pale cyst nematode Globodera pallida (Stone) Behrens and the golden nematode G. rostochiensis (Wollenweb.) Behrens have been introduced into Canada (see Introduced diseases and pests, 3.11). Both species occur in Newfoundland, and the golden nematode also occurs on Vancouver Island (see Potato, 16.36). The root-lesion nematode Pratylenchus penetrans (Cobb) Filip. & Stek. affects most of the major vegetable crops grown in Canada (see Potato, 16.38). The stem and bulb nematode Ditylenchus dipsaci (Kuhn) Filip. attacks mainly onion and allied crops. It has been confirmed from Newfoundland, Ontario, Saskatchewan and British Columbia (see Onion,
13.24). The sugarbeet cyst nematode Heterodera schachtii Schmidt occurs at scattered locations across Canada. It can affect beet, spinach, rhubarb and cruciferous crops (see Beet, 5.14).
Ectoparasitic nematodes - These nematodes feed on root tissues, such as the epidermis and cortex and, if their stylet is long enough, the vascular tissue. They rarely enter the roots of plants. They include the stubby-root nematodes Paratrichodorus allii (Jensen) Siddiqi, P. pachydermus (Seinhorst) Siddiqi, other Paratrichodorus spp., and Trichodorus spp. These nematodes have caused only minor damage to a few gardens in southern Alberta (see Potato). Other ectoparasitic nematodes include the dagger nematodes Xiphinema spp., the needle nematodes Longidorus spp., the pin nematodes Paratylenchus spp., the spiral nematodes Rotylenchus spp. and Helicotylenchus spp., and the stunt nematodes Tylenchorhynchus spp., Merlinius spp., Amplimerlinius spp., and Gracilacus spp. These nematodes are prevalent in some Canadian
vegetable fields and often are identified from soil samples, but they are rarely a serious problem. At numbers as high as 5000 or more per kilogram of soil, pin nematodes have reduced yields of rhubarb in Ontario. Dagger and needle nematodes prefer hosts with woody roots and are more frequently associated with strawberry, raspberry, grapes and roses than with vegetable crops, which tend to be more soft-rooted.
Damage caused by plant-parasitic nematodes is often difficult to distinguish from that caused by other pathogens or by abiotic factors. Stunting, chlorosis and early senescence also can indicate a problem with soil nutrition, watering, or a soil-borne pathogen; these conditions need not necessarily be nematode-related. Proliferation of secondary roots, a symptom of attack by some nematodes, also may result from the branching of the tips of young roots of some vegetables in the presence of such unfavorable soil conditions as soil compaction, insufficient decomposition of organic plant residues, extremes in moisture content, poor fertility, and frost heaving. Some nematode problems can be assessed by visual examination of plant tissue. In many cases, however, nematode problems can only be determined after soil sampling and extraction; both procedures are time-consuming and expensive. Nematodes do not spread very rapidly, and a minor infestation may not result in visible symptoms or reduced productivity.
Table 2.3a. Host ranges of economically important nematode pests on vegetable crops in Canada
Crop RKN* RLN PCN SBN SRN SCN Bean X X X
Beet, chard and spinach X X X Carrot X X
Celery and celeriac X X
Crucifers X X X X Cucurbits X X
Ginseng X X t
Greenhouse cucumber X X
Greenhouse lettuce X X
Greenhouse pepper X X
Greenhouse tomato X X
Lettuce, chicory and endive X X
Maize (sweet corn) X X
Onion and other allium crops X X X
Parsnip X
Pea X X X
Potato X X X X
Rhubarb X X X Tomato, eggplant and pepper X X X X
*RKN = Root-knot nematode (Meloidogyne hapla Chitwood); RLN = Root-lesion nematode (Pratylenchus penetrans (Cobb) Filip. & Stek.); PCN = Potato cyst nematodes (Globodera spp.); SBN = Stem and bulb nematode (Ditylenchus dipsaci (Kuhn) Filip.); SRN = Stubby-root nematodes (Paratrichodorus and Trichodorus spp.) SCN = Sugarbeet cyst nematode (Heterodera schachtii Schmidt).
t The root-lesion nematode is regarded as a potentially serious pest of ginseng in British Columbia.
Selected references
Brodie, B.B. 1984. Nematode parasites of potato. Pages 167–212 in W.R. Nickle, ed., Plant and Insect Nematodes. Dekker, New York, NY. 925 pp.
Daulton, R.A., and C.J. Nusbaum. 1961. The effect of soil temperature on the survival of the root-knot nematodes Meloidogyne javanica and M. hapla. Nematologica 6:280–294. Harranger, J. 1972. Les nématodes des cultures mara?chères. Phytoma 241:13–22.
Hijink M.J., and R.W. Suatmadji. 1967. Influence of different Compositae on population density of Pratylenchus penetrans and some other root infesting nematodes. Neth. J. Plant Pathol.
73:71–82.
Jensen, H.J. 1972. Nematode pests of vegetable and related crops. Pages 377–408 in J.M.
Webster, ed., Economic Nematology. Academic Press, New York. 563 pp.
Mai, W.F., J.R. Bloom, and T.A. Chen, eds. 1977. Biology and Ecology of the Plant Parasitic Nematode Pratylenchus penetrans. Pennsylvania Univ. Coll. Agric., University Park,
Pennsylvania. 64 pp.
Richard-Molard, M. 1982. Les nématodes de la betterave. Cultivar 1982 (Juin):61–63. Townshend, J.L. 1962. The root-lesion nematode, Pratylenchus penetrans (Cobb, 1917) Filip. & Stek. 1941, in celery. Can. J. Plant Sci. 42:314–322.
Townshend, J.L., J.W. Potter, C.F. Marks, and A. Loughton. 1973. The pin nematode, Paratylenchus projectus, in rhubarb in Ontario. Can. J. Plant Sci. 53:377–381.
Vrain, T.C., and M. Dupre. 1982. Distribution des nématodes phytoparasites dans les sols mara?chers du sud-ouest du Québec. Phytoprotection 63:79–85.
Wallace, H.R. 1973. Nematode Ecology and Plant Disease. Crane Russak, New York, NY. 228 pp.
Wong, T.K., and W.F. Mai. 1973. Pathogenicity of Meloidogyne hapla to lettuce as affected by inoculum level, plant age at inoculation and temperature. J. Nematol. 5: 126–129.
Insects
Many species of insects, mites, spiders, millipedes, centipedes and like animals, collectively known as arthropods, are present in the plant ecosystem. Only a relatively small proportion of insect species feed or have a detrimental effect on vegetable plants, and only a few of those that feed on vegetable plants are economically important pests; a large proportion occur in small numbers, feed very sporadically, or cause only minor, indirect damage. Nevertheless, the relatively few insect species that are economically important pests, often only one, two or three on a plant species, can destroy a crop or cause sufficient damage to render it unmarketable or unprofitable to grow unless the pest populations are regulated. A list of the major groups of insects associated with vegetable crops in Canada is given in Table 2.3b.
Insects are a diverse group of six-legged invertebrates that undergo complete, gradual or no change of form (metamorphosis) during development. Insects and their close relatives, spiders and mites, are animals that have jointed legs. Adult insects have three body regions (head, thorax and abdomen), three pairs of legs, one pair of antennae, complex mouthparts, and frequently two pairs of wings. The skin of an insect is the external skeleton, which covers the whole body. This exoskeleton must be shed from time to time (molting) as the insect grows.
Life cycle - All insects have an egg and an adult stage. A few, such as springtails, do not undergo metamorphosis; the juveniles resemble adults but are smaller. Juveniles that resemble
the adult stage except that they lack wings or have underdeveloped wings are called nymphs; insects that have egg, nymph and adult stages are said to undergo gradual metamorphosis; examples include earwigs, aphids, plant bugs and whiteflies. Juvenile forms that do not resemble the adult stage are called larvae; in some larvae, the thoracic legs are underdeveloped, while others have legs in the abdominal region, and some have no legs at all. Certain types of larvae have distinctive names; larvae of moths and butterflies are called caterpillars, while caterpillars in which some of the abdominal legs are missing are termed loopers; larvae of beetles are known as grubs, and the legless larvae of flies are called maggots. Insects that have egg, larval, pupal and adult stages are said to undergo complete metamorphosis. The juvenile forms (larva or nymph) grow in steps called instars; at the end of each instar they molt, then swell to the new size; the new outer skin hardens and remains unchanged until the next molt. The number of molts varies with the species. The last instar typically spins a cocoon or forms a puparium from which the insect emerges in its adult form. Insects may overwinter in the egg, larval, pupal or adult stage. Juvenile stages usually do the most serious damage to plants, but many adult insects also can inflict damage. It is important in devising appropriate pest management strategies to be able to recognize the different stages of insect development.
The most common, foliage-eating insect pests are larvae of moths and butterflies (Lepidoptera) and larvae and adults of beetles (Coleoptera); nymphs and adults of grasshoppers and other related species (Orthoptera) also may consume foliage. Aphids and leafhoppers (Homoptera), plant bugs (Heteroptera) and thrips (Thysanoptera) have piercing or piercing-and-sucking mouthparts in the nymphal and adult stages and may cause extensive damage to vegetable crops; many of these insects have a major role in transmission of pathogens, especially viruses. Larvae of flies (Diptera) feed and burrow into roots, bulbs and stems of plants and are important pests of root crops, such as carrot, onion and rutabaga, and of several other crops, including cabbage and cauliflower, on which they feed on the roots and stems, and bean and corn, where they feed on the germinating seeds and seedlings. A great many insects also are beneficial, feeding on other pest species of insects as predators or as parasites (see Beneficial insects, mites and pathogens, 3.7). A key to the principal orders of insects associated with vegetable crops in Canada is given in Table 2.3c.
Mites and spiders
Adult mites and spiders characteristically have four pairs of jointed legs; exceptions include the rust mites and the blister mites, which have only two pairs of legs. Unlike insects, they lack antennae and have only two body regions, the cephalothorax and abdomen. Spiders are predators, chiefly of insects. The spider-like daddy longlegs, or harvestman, which is related to mites and spiders, is commonly seen around home gardens. It also is a beneficial predator of small organisms, including insects.
Female mites deposit eggs, which hatch into six-legged larvae. The larvae feed and molt to form eight-legged nymphs, of which there are several forms, before the adult stage is reached. In some species the females give birth to live young. Because of their small size, mites often are not noticed. Many are scavengers and some are predators. Many species have rasping and sucking mouthparts and may damage vegetable crops, not only by weakening the plant by sucking out sap, but also by destroying cells and by aiding entry and transmission of pathogenic microorganisms. The two-spotted spider mite is the most important species on vegetable crops in
Canada, both in the field and in greenhouses. Some mites are predatory and are being used to control pest mites and thrips in greenhouses (see Beneficial insects, mites and pathogens, 3.7). Centipedes and millipedes
These animals, sometimes confused with insects, are encountered in the garden or compost. Centipedes are somewhat flattened, have 15 or more pairs of legs, with one pair per body segment, and their antennae (one pair) are long and have 14 or more sub-divisions. Millipedes (12.21T1) are cylindrical, have two pairs of legs on each segment except the first several segments following the head, which have only a single pair, and their antennae (one pair) are short, usually with seven sub-divisions. Centipedes are poisonous predators of insects and are usually faster moving than millipedes, which feed primarily on dead plant remains and tend to coil when disturbed.
Table 2.3b. Characteristics of major groups of insects associated with vegetable crops in Canada
Order Common Name Mouthparts Metamorphosis Collembola springtails chewing none Orthoptera grasshoppers, crickets chewing gradual Dermaptera earwigs chewing gradual Thysanoptera thrips piercing gradual Homoptera aphids, leafhoppers piercing-sucking gradual Heteroptera stink bugs, plant bugs piercing-sucking gradual Coleoptera beetles, weevils chewing complete Lepidoptera butterflies, moths chewing (larvae)complete Hymenoptera ants, bees, wasps chewing complete Diptera flies rasping (larvae)complete
Symphylans
Symphylans are small, flattened, white animals that resemble centipedes. They are less than 8 mm long. The adults have 10 to 12 pairs of legs (centipedes have 15 or more pairs), a pair of unbranched antennae, and a pair of hair-like appendages on the last segment. They feed chiefly on microorganisms and plant material in the soil, but they also may feed on the roots of plants, especially in moist soils that are high in organic matter. Damage to root hairs and roots may facilitate the entry of plant pathogens.
Slugs and snails
All land snails and most slugs have a calcareous shell. In snails the shell is external and twisted
in a continually increasing spiral, usually clockwise. The shell takes many forms among different species. The shell aperture (“mouth”) in all land snails in Canada lacks a cover (operculum). In some snail groups, identification is based on characteristics of soft anatomy. In slugs, the shell is internal, and characteristics of the fleshy body are used in identification; these include the position of the breathing pore, the presence of a groove in the mantle, the ridge (keel) on the back, the caudal mucal pore, the color and pigmentation of the body, and the color of the mucus.
Both slugs and snails may be plant pests in damp situations. They both glide on a slime trail of secreted mucus. Mouthparts are rasping, and most damage is done at night or on cloudy days. Under dry conditions, eggs of slugs may remain unhatched for long periods. Young snails remain close to the area in which they were hatched for several months and may take many months to mature. The brown garden snail, which was introduced into British Columbia, is edible but is regarded as a pest in Canada (see Introduced diseases and pests, 3.11).
Sowbugs and pillbugs These are crustaceans adapted to living out of water but in damp environments. They are oval, with a small head, two pairs of antennae, seven pairs of jointed, similar (isopod) legs and a dorsoventrally flattened body that is composed of hard, overlapping plates. They can be distinguished by the ability of the pillbug to curl into a ball, and by the two tail-like appendages on the sowbug. Both are active decomposers of rotting vegetation. They may cause problems in certain situations where vegetables, such as cucurbits, rest on moist ground or where young seedlings are slow to develop in cool, moist weather. These crustaceans have not been implicated in transmission of diseases in vegetable crops.
Table 2.3c. Key to the principal orders of insects associated with vegetable crops in Canada This key should be applicable to adults and most nymphs and larvae of the groups indicated
1.Winged
Wings entirely or partly membranous with veins (2)
la.Winged or wingless
If winged, forewing (FW) thickened throughout (7)
2.Wings with scales
Mouthparts coiled............................................................................butterflies and moths 2a.Wings lacking scales
Mouthparts not coiled (3)
3.FW only, hind wing (HW) greatly reduced.................................................................flies 3a.FW and HW same size or HW only slightly smaller (4)
4.Wings narrow, fringed around the margin
Body less than 5 mm in length
Legs (tarsi) without claws ........................................................................................thrips 4a.Wings broad, without fringe around margin
Body more than 5 mm in length
Legs (tarsi) with a pair of claws (5)
5.Tarsi with 5 sub-segments (tarsomeres)
Mouthparts for chewing
HW with tiny hooks (hamuli) along leading edge ..............winged ants, bees and wasps 5a. Tarsi with only 2 or 3 tarsomeres
Mouthparts for sucking
HW without hamuli along leading edge (6)
6.Mouthparts arising at front of head
Immatures with wing buds
Adult FW membranous over outer half,........................................plant bugs, stink bugs and thickened over inner half.
6a.Mouthparts arising beneath head
Immatures with wing buds (as above)
Adult FW membranous or thickened throughout...............................aphids, leafhoppers Adult FW membranous with a waxy coating.....................................................whiteflies 7.FW hard or leathery, covering HW. (8)
7a. Entirely wingless (11)
8. Abdomen with forceps-like appendages (cerci)....................................................earwigs 8a. Abdomen lacking cerci or cerci not forceps-like. (9)
9. Mouthparts adapted for piercing-sucking...................................true bugs (go back to 6) 9a. Mouthparts adapted for chewing (10)
10.FW thickened or leathery with veins
Wings held roof-like over abdomen or overlapping with HW folded lengthwise fan-like Cerci present, straight
Antennae short..............................................................................................grasshoppers Antennae long, filamentous.............................................................crickets and katydids 10a. FW hardened (elytron) and without obvious venation
Wings held flat over abdomen FW's meeting in a straight line HW folded crosswise, not fan-like
Cerci absent.........................................................................................................beetles 11.Body narrow-waisted
Antennae elbowed.......................................................................wingless ants and wasps 11a.Body broad-waisted
Antennae not elbowed (12)
11b.Body fleshy and larva-like, lacking division into thorax and abdomen by a waist Antennae inconspicuous or absent (16)
12.Abdomen with a spring (furcula)......................................................................springtails 12a.Abdomen lacking furcula.. (13)
Abdomen with a pair of dorsal projections (cornicles)
Body plump, not narrow
Adults and nymphs may be present..................................wingless aphids (go back to 6) 13a. Abdomen lacking cornicles
Body narrow, not plump and less than 5 mm in length (14)
14.Tarsi lacking claws.............................................................................thrips (go back to 4) 14a.Tarsi with claws. (15)
15.Antennae 4- or 5-segmented
Mouthparts for piercing-sucking (from front of head)
Cerci absent......................................................plant bug, young nymph (go back to 6) 15a.Antennae with many more than 5 segments (filamentous)
Mouthparts for chewing
Cerci present cricket, young nymph.........................................................(go back to 10) 16.Body with a capsule-like head and legs
Head lacking compound eyes
Mouthparts for chewing, moveably attached to head (17)
16a. Body lacking a head capsule and legs
Mouthparts in form of mouthhooks, retractable................................fly larvae (maggots) 17.Head with 1-6 simple eyes (ocelli) on each side
Body with segmented legs (3 pairs) anteriorly
Body with fleshy legs (2-5 pairs) posteriorly ......butterfly and moth larvae (caterpillars) Note: sawfly larvae, which have I simple eye on each side of the head and may be
mistaken for caterpillars, do not have representatives on vegetable crops in
Canada.
17a. Head lacking simple eyes
Body with segmented legs (3 pairs) anteriorly
Body lacking fleshy legs posteriorly....beetle larvae (wireworms, white grubs and other beetle grubs)
(Original by J.A. Garland)
Weeds (Figs. 2.3a–q)
Weeds generally are considered to be plants growing where they are not desired. They sometimes can be as serious a threat to vegetable crops as diseases and other pests, and they occur wherever vegetable crops are grown in Canada. Successful vegetable production often depends upon the integration of weed management (see 3.13) with other pest management strategies.
Vegetable crops vary widely in their response to weed competition, ranging from non-competitive crops, such as onion, to moderately competitive crops, such as potato and transplanted cabbage. Studies in Canada have shown that direct-seeded onion does not produce marketable bulbs if weeds are not controlled. In southern Alberta, the time from seeding to the two-leaf stage in onion averages 46 days; during that time, wild mustard can emerge, complete its vegetative growth, and flower.
The critical period of weed competition in vegetable crops is the minimum time that weeds must be suppressed to prevent yield losses. In a southern Ontario study, cucumber yields were reduced if the crop was not kept weed-free for up to four weeks after seeding, or if it was weedy for more than three to four weeks. In another trial, the critical period for pickling cucumber ranged from two to five weeks after seeding. In Prince Edward Island, the critical period for rutabaga is two to four weeks after crop emergence when barnyard grass (2.3a) and lamb's-quarters (2.3f,q) are present. Similarly in Quebec, the critical period for carrot crops grown on organic soils was found to be between three and six weeks after crop emergence. Although the concept of a critical weed period has practical limitations because crops and weeds grow at different rates from year to year, early removal of weeds is clearly important in reducing losses from competition. In addition to their direct competition in crop growth, weeds are important reservoirs of most crop viruses and their insect and nematode vectors, and of pathogenic fungi and bacteria. Because of their density and proximity to crop plants, weeds also provide microclimates conducive to infection by fungi and bacteria.
Chemical weed control treatments have been developed mainly for field crops in which the soil becomes shaded early in their development. Many vegetable crops, on the other hand, do not provide rapid shading of the soil around them and weeds continue to germinate over a longer period of time. The continued emergence of weeds necessitates additional tillage, which disturbs the soil and stimulates more weed seeds to germinate, perpetuating the problem.
The weeds most commonly encountered in vegetable fields in Canada are listed in Table
2.3d. Weed problems in vegetable crops are often regional. In the Prairie provinces, for instance, vegetables occasionally follow cereals and, hence, volunteer barley or wheat can be a problem, especially after a dry autumn. In eastern Canada, cereals are sometimes used as cover crops or form part of a stale-seedbed treatment for weed control. Other examples of regional weed problems include: eastern black nightshade, hairy galinsoga, velvetleaf (Abutilon theophrasti Medik.) and large crabgrass (Digitaria sanguinalis (L.) Scop.) in southern Ontario; kochia (Kochia scoparia L.) (2.3e) in southern Alberta and hemp nettle (Galeopsis tetrahit L.) in central Alberta; barnyard grass (2.3a) in New Brunswick; common groundsel (Senecio vulgaris L.) (2.3d) in Newfoundland; and creeping yellow cress (Rorippa sylvestris (L.) Besser) in the Fraser Valley of British Columbia.
Table 2.3d. Weeds commonly occurring in vegetable crops in Canada
Common Name Scientific Name
Annual grasses
Barley, volunteer Hordeum vulgare L.
Barnyard grass Echinochloa crusgalli (L.) Beauv.
Crabgrass Digitaria spp.
Foxtail, green Setaria viridis (L.) Beauv.
Foxtail, yellow Setaria glauca (L.) Beauv.
Wheat, volunteer Triticum aestivum L.
Broadleaved annual weeds
Buckwheat, wild Polygonum convolvulus L.
Chickweed Stellaria media (L.) Cyrill
Cudweed, low Gnaphaliu muliginosum L.
Flower-of-an-hour Hibiscus trionum L.
Galinsoga, hairy Galinsoga ciliata (Raf.) Blake
Groundsel, common Senecio vulgaris L.
Lamb's-quarters Chenopodium album L.
Mallow, round-leaved Malva rotundifolia L.
Mustard, wormseed Erysimum cheiranthwoides L.
Mustard, wild Brassica kaber (DC.) Wheeler
Nightshade, black Solanum nigrum L.
Nightshade, eastern black Solanum ptycanthum Dun.
Nightshade, hairy Solanum sarrachoides Sendt.
Pigweed, red root Amaranthus retroflexus L.
Pigweed, prostrate Amaranthus graecizans L.
Purslane, common Portulaca oleracea L.
Radish, wild Raphanus raphanistrum L.
Ragweed, common Ambrosia artemisiifolia L.
Shepherd's-purse Capsella bursa-pastoris (L.)
Smartweeds, annual Polygonum spp.
Spurry, corn Spergula arvensis L.
Perennial weeds
Bindweed, field Convolvulus arvensis L.
Milkweed, common Asclepias syriaca L.
Mint, field Mentha arvensis L.
Quack grass Agropyron repens (L.) Beauv.
Thistle, Canada Cirsium arvense L.
Thistle, sow Sonchus arvensis L.
Parasitic higher plants
More than 2500 species of higher plants are known to live parasitically on other plants. These parasitic plants belong to several different botanical families and vary greatly in their dependence on their host plants. Relatively few of the known higher parasitic plants cause diseases on agricultural crops. In Canada, only dodder (Cuscuta sp.) has been observed as a pest in field-grown crops, and only very rarely has it been found in vegetables. In the United States, dodder has been reported to occasionally cause economic losses in carrot, onion, tomato, sugar beet, potato, hops, peppermint and pepper. Dodder forms dense tangles of leafless strands on and through the crowns of host plants (2.3T1). It reduces the growth and yield of affected plants.
2.4 Climate and environment
Pest distribution
The plant pathogens, insects, mites and other pests that attack and damage vegetable crops in Canada often are the same as those found on the same crops grown in similar climates in other countries. However, the climatic tolerances and other characteristics of pathogens may be altered as they adapt to climate, soil and other factors in Canadian production areas. Similarly, insect and other pests are influenced by climate, often resulting in pest complexes that are substantially different from those in other production areas. Indeed, because Canadian production areas are near the northern limit of distribution of some pest species, their population fluctuations and numbers differ from those nearer the main area of distribution, partly because parasitic and predaceous species, themselves, may not be as functional in Canada. It is apparent, therefore, that some species of pathogens and pests that are common elsewhere may be of minor importance on the crops grown in Canada; they may be secondary or occasional, or they may not be noticed at all. Others, however, may be devastating.
Environment-related disorders
All crop plants have an optimum total environment for productivity; any environmental factors departing markedly from that optimum will decrease yield and, by causing stress to the plants, may make them more susceptible to diseases and pests. Heavy yields also may stress plants by diverting photosynthetic products and other nutrients to the harvested organs (fruit, tubers, roots, leaves) at the expense of other parts of the plant. Many vegetables are raised from transplants, often started in greenhouses or distant geographical areas, and sometimes they are poorly acclimatized, so that they, too, are severely stressed at transplanting, being more susceptible, for example, to late spring frosts or heat damage, particularly on sandy soils.
Other environmental factors that can have minor or disastrous effects on crops include: too much or too little water, poor soil structure and compaction from machinery, poor drainage, heat, cold (including frost), wind, hail, lightning, and industrial pollutants in air, soil and water.
Chemical injury
Experienced extension personnel know that a high proportion of crop damage can be attributed to chemical injury; for example, too much or the wrong fertilizer, or too much or the wrong pesticide. Often, these situations result from simple, arithmetical errors in calculating rates of application, or by applying pesticides on the assumption that twice as much might be twice as good. Indeed, all materials with a '-cide' suffix can damage non-target organisms and, even at the recommended rates, may reduce yield to an extent that is scarcely compensated for by the control of weeds, insects or pathogens. Not infrequently, herbicide damage occurs simply because various pesticides have been applied from the same sprayer without thoroughly cleaning it after each use.
All fertilizers and pesticides should be applied strictly in accordance with the manufacturer's directions and local expert advice, and with appropriate care to avoid exposure of non-target organisms, including workers and the public. To avoid environmental contamination, precautions about spraying in windy conditions, disposing of pesticide containers, and avoiding contamination of ground water and reservoirs should be observed.
Nutritional disorders
In addition to the gross effects of nitrogen-phosphate-potassium (NPK) fertilizers, there are many disorders of vegetable crops that are caused by excesses or deficiencies of the so-called minor or trace elements. The availability of the essential elements to plants depends largely on soil type and environmental conditions. For example, phosphorus is less available to plants in heavy than in light soils; magnesium becomes deficient in sandy soils leached by heavy rains and irrigation; boron is less available in limed and dry soils; and iron and manganese both become more available in acidic soils. Indeed, manganese toxicity can occur in very acidic soils. Various elements can affect the availability of others; for example, iron availability is depressed by an excess of phosphate. Some of these effects are magnified in greenhouse soils, which are heavily amended with organic materials and may be steam-sterilized. Steaming releases toxic amounts of manganese and ammonia, and steamed soils generally have to be leached before use for those reasons. It is strongly recommended that vegetable soils be sampled regularly for chemical analysis in order to determine exact fertilizer requirements. It is particularly important to provide the proper amounts of calcium and potassium because they enhance the natural resistance of plants to some diseases.
Additional references
Anderson, R.V., and R.H. Mulvey. 1979. Plant-parasitic Nematodes in Canada; Part 1. An Illustrated Key to the Genera. Agric. Can. Res. Br. Monogr. 20. 152 pp.
Anderson, R.V., and J.W. Potter. 1991. Stunt nematodes: Tylenchorhynchus Merlinius, and related genera. Pages 529–586 in W.R. Nickle, ed., Manual of Agricultural Nematology.
Dekker, New York. 1035 pp.
Borror, D.J., and R.E. White. 1970. A Field Guide to the Insects of America North of Mexico.
Houghton Mifflin Co., Boston, MA. 404 pp.
Brown, R.H., and B.R. Kerry, eds. 1987. Principles and Practices of Nematode Control in Crops. Academic Press, New York, NY. 447 pp.
Dawson, J.H., F.M. Ashton, W.V. Welker, J.R. Frank, and G.A. Buchanan. 1984. Dodder and Its Control. U.S. Dep. Agric., Farmers' Bull. 2276. 24 pp.
Esser, R.P. 1991. A computer-ready checklist of the genera and species of phytoparasitic nematodes, including a list of mnemonically coded subject categories. Florida Dep. Agric.
Consumer Serv. Bull. 13. 185 pp.
Gubina, V.G. 1988. Nematodes of Plants and Soils: Genus Ditylenchus. Saad Publications, Karachi. 397 pp.
Mulvey, R.H., and A.M. Golden. 1983. An illustrated key to the cyst-forming genera and species of Heteroderidae in the western hemisphere with species morphometrics and distribution. J.
Nematol. 15: 1–59.
Nickle, W.R., ed. 1984. Plant and Insect Nematodes. Dekker, New York, NY. 925 pp. Nickle, W.R., ed. 1991. Manual of Agricultural Nematology. Dekker, New York, NY. 1035 pp. Pimentel, D., ed. 1991. Handbook of Pest Management in Agriculture. Vol. 2. CRC Press, Boca Raton, Florida. 773 pp.
Webster, J.M., ed. 1972. Economic Nematology. Academic Press, New York. NY. 563 pp.
实验13、CoolEdit数字音频处理 实验课时： 课内：2课时；课外：1课时 实验目的： 了解音频数据的特性及其获取和处理的方法，学会使用音频编辑工具CoolEdit进行音频数据的录制、编辑和播放 实验内容： 操作准备 1.在D:或E:分区创建一个以你的“完整学号+姓名”命名的文件夹（名称应类似： 198009010001文立斌），我们把这个文件夹简称为“你的文件夹” 2.以下操作步骤中所涉及的198009010001、文立斌均应替换成你的学号、姓名 3.准备好音频实验环境，个别人物需要准备麦克风、音箱（或耳机） 任务一、音频提取 1.打开CoolEditPro软件 2.如下图所示，单击工具栏最左边的按钮切换到波形编辑界面 → 3.依次执行菜单命令【文件】→【从视频文件中提取】，通过系统显示的“选择视频文件” 对话框选定“说唱脸谱.dat”文件后单击【打开】按钮，系统开始从“说唱脸谱.dat” 中提取音频 4.等待系统提取音频结束后，执行菜单命令【文件】→【另存为】，将提取到的波形保存 为类似“文立斌A.wma”（.wma格式）的文件 任务二、淡入淡出 1.打开CoolEditPro软件 2.如下图所示，单击工具栏最左边的按钮切换到波形编辑界面 → 3.依次执行菜单命令【文件】→【打开】，通过系统显示的“打开波形文件”对话框选定 “最炫民族风.mp3”文件后单击【打开】按钮打开该文件，原始波形编辑面板类似：
4.单击视窗左下角录播工具面板中的播放按钮，试听歌曲，确定演唱（人声）从何时（第 几秒）开始——大约是第23秒！ 5.如下图所示，在波形编辑面板中以鼠标拖拽的方式选定最前面23秒波形： 如果需要精确选定波形区域，您还可以借助视窗右下角的如下面板，直接输入始末时间： 6.依次执行菜单命令【效果】→【波形振幅】→【渐变】，如下图所示，在“波形振幅” 对话框中，选择“Fade in”（淡入），然后单击【确定】按钮： 7.系统进行淡入处理后的波形类似： 您应该对照一下处理前后的前23秒波形的异同 8.试听，您应该能听到淡入处理的效果（音量越来越大）才对！ 9.从4分20秒位置开始选定直到音频结束处的波形，为选定的波形添加淡出效果，处理 第2页
第二章原核微生物 一、名词解释: 原核微生物;芽孢;菌落;细菌L型;伴孢晶体;糖被 二、填空题 I.证明细菌存在细胞壁的主要方法有_______,________,________与____等4种。 2.细菌细胞壁的主要功能为_____,______,______与______等。 3.革兰氏阳性细菌细胞壁的主要成分为_____与_____,而革兰氏阴性细菌细胞壁的主要成分则就是_____、_____、______与______。 4.肽聚糖单体就是由____与____以_____糖苷键结合的_____,以及_____与____3种成分组成的,其中的糖苷键可被_____水解。 5.G+细菌细胞壁上磷壁酸的主要生理功能为_____、_____、_____与_____等几种。 6.G-细菌细胞外膜的构成成分为_____、_____、_____与_____。 7.脂多糖(LPS)就是由3种成分组成的,即_____、_____与_____。 8.在LPS的分子中,存在有3种独特糖,它们就是_____、____与____。 9.用人为方法除尽细胞壁的细菌称为____,未除尽细胞壁的细菌称为____,因在实验室中发生 缺壁突变的细菌称为_____,而在自然界长期进化中形成的稳定性缺壁细菌则称为_____。 10.细胞质膜的主要功能有______、______、_____、______与______。 三、选择题: 1.G-细菌细胞壁的最内层成分就是( )。 (1)磷脂(2)肽聚糖(3)脂蛋白(4)LPS 2.G+细菌细胞壁中不含有的成分就是( )。 (1)类脂(2)磷壁酸(3)肽聚糖(4)蛋白质 3.肽聚糖种类的多样性主要反映在( )结构的多样性上。 (1)肽桥(2)黏肽(3)双糖单位(4)四肽尾 4.磷壁酸就是( )细菌细胞壁上的主要成分。 (1)分枝杆菌(2)古生菌(3)G+ (4)G- 5.在G—细菌肽聚糖的四肽尾上,有一个与G+细菌不同的称作( )的氨基酸。 (1)赖氨酸(2)苏氨酸(3)二氨基庚二酸(4)丝氨酸 6.脂多糖(LPS)就是G+细菌的内毒素,其毒性来自分子中的( )。 (1)阿比可糖(2)核心多糖(3)O特异侧链(4)类脂A 7.用人为的方法处理G—细菌的细胞壁后,可获得仍残留有部分细胞壁的称作( )的缺壁细 菌。 (1)原生质体(2)支原体(3)球状体(4)L型细菌 8.异染粒就是属于细菌的( )类贮藏物。 (1)磷源类(2)碳源类(3)能源类(4)氮源类 9.最常见的产芽孢的厌氧菌就是( )。 (1)芽孢杆菌属(2)梭菌属(3)孢螺菌属(4)芽孢八叠球菌屑 10.在芽孢的各层结构中,含DPA—Ca量最高的层次就是( )。 (1)孢外壁(2)芽孢衣(3)皮层(4)芽孢核心 四、判断题 1.古生菌也就是一类原核生物。 2.G+细菌的细胞壁,不仅厚度比G-细菌的大,而且层次多、成分复杂。
实验报告 课程名称数字音视频原理 实验题目MATLAB音频文件处理 专业电子信息工程 班级3班 学号09080323 学生姓名王志愿 实验成绩 指导教师吴娱 2012年3月 一、实验目的 1、掌握录制语音信号的基本过程； 2、掌握MATLAB编程对语音信号进行简单处理的方法并分析结果。 二、实验要求
上机完成实验题目，独立完成实验报告。 三、实验内容 1、问题的提出：数字语音是信号的一种，我们处理数字语音信号，也就是对一种信号的处理，那信号是什么呢？ 信号是传递信息的函数。离散时间信号（序列）——可以用图形来表示。 按信号特点的不同，信号可表示成一个或几个独立变量的函数。例如，图像信号就是空间位置（二元变量）的亮度函数。一维变量可以是时间，也可以是其他参量，习惯上将其看成时间。信号有以下几种： （1）连续时间信号：在连续时间范围内定义的信号，但信号的幅值可以是连续数值，也可以是离散数值。当幅值为连续这一特点情况下又常称为模拟信号。实际上连续时间信号与模拟信号常常通用，用以说明同一信号。 （2）离散时间信号：时间为离散变量的信号，即独立变量时间被量化了。而幅度仍是连续变化的。 （3）数字信号：时间离散而幅度量化的信号。 语音信号是基于时间轴上的一维数字信号，在这里主要是对语音信号进行频域上的分析。在信号分析中，频域往往包含了更多的信息。对于频域来说，大概有8种波形可以让我们分析：矩形方波，锯齿波，梯形波，临界阻尼指数脉冲波形，三角波，余弦波，余弦平方波，高斯波。对于各种波形，我们都可以用一种方法来分析，就是傅立叶变换：将时域的波形转化到频域来分析。 2、设计方案： 首先要对声音信号进行采集，Windows自带的录音机程序可驱动声卡来采集语音信号，并能保存成.WAV格式文件，供MATLAB相关函数直接读取、写入或播放。 利用MATLAB中的wavread命令来读入（采集）语音信号，将它赋值给某一向量。再将该向量看作一个普通的信号，对其进行FFT变换实现频谱分析，再依据实际情况对它进行滤波。对于波形图与频谱图（包括滤波前后的对比图）都可以用MATLAB画出。我们还可以通过sound/wavplay命令来对语音信号进行回放，以便在听觉上来感受声音的变化。 3、主体部分： （1）语音的录入与打开： [x,fs,bits]=wavread('d:\1.wav');%用于读取语音，采样值放在向量x中，fs 表示采样频率(Hz)，bits表示量化位数。
第二章《原核微生物》习题 一、名词解释 1．细菌： 2．聚-β-羟丁酸(poly-β-hydroxybutyric acid，PHB ) 3．异染粒(metachromatic granules) 4．羧酶体(carboxysome) 5．芽孢(spore) 6．渗透调节皮层膨胀学说 7．伴孢晶体（parasporal crystal） 8．荚膜（capsule） 9．原核生物： 10．古生菌(archaea) 11．L型细菌 12．鞭毛(flagella) 13．富营养化(eutrophication)： 14．假肽聚糖 15．蓝细菌： 16．支原体。 17．立克次氏体 18．衣原体 二、填空题 1．证明细菌存在细胞壁的主要方法有，，和。 2．细菌细胞壁的主要功能为，，和等。 3．革兰氏阳性细菌细胞壁的主要成分为和，而革兰氏阳性细菌细胞壁的主要成分则是，，和。 4．肽聚糖单体是由和以糖苷键结合的，以及和 3种成分组成的，其中的糖苷键可被水解。 5．G+细菌细胞壁上磷壁酸的主要生理功能为，，和等几种。 6．G-细菌细胞外膜的构成成分为，，和。 7．脂多糖（LPS）是由3种成分组成的，即，和。 8．在LPS的分子中，存在有3种独特糖，它们是，和。 9．用人为方法除尽细胞壁的细菌称为，未除尽细胞壁的细菌称为，因在实验室中发生缺壁突变的细菌称为，而在自然界长期进化中形成的稳定性缺壁细菌则称为。 10．细胞质膜的主要功能有，，，和。 三、选择题 1．G细菌细胞壁的最内层成分是（）。 （1）磷脂；（2）肽聚糖；（3）脂蛋白；（4）LPS 2．G+细菌细胞壁中不含有的成分是（）。 （1）类脂；（2）磷壁酸；（3）肽聚糖；（4）蛋白蛋 3．肽聚糖种类的多样性主要反映在（）结构的多样性上。 （1）肽桥；（2）黏肽；（3）双糖单位；（4）四肽尾 4．磷壁酸是（）细菌细胞壁上的主要成分。 （1）分枝杆菌；（2）古生菌；（3）G+；（4）G-
第二章原核微生物 一、名词解释： 原核微生物；芽孢；菌落；细菌L型；伴孢晶体；糖被 二、填空题 I．证明细菌存在细胞壁的主要方法有_______，________，________和____等4种。2．细菌细胞壁的主要功能为_____，______，______和______等。 3．革兰氏阳性细菌细胞壁的主要成分为_____和_____，而革兰氏阴性细菌细胞壁的主要成分则是_____、_____、______和______。 4．肽聚糖单体是由____和____以_____糖苷键结合的_____，以及_____和____3种成分组成的，其中的糖苷键可被_____水解。 5．G+细菌细胞壁上磷壁酸的主要生理功能为_____、_____、_____和_____等几种。6．G-细菌细胞外膜的构成成分为_____、_____、_____和_____。 7．脂多糖(LPS)是由3种成分组成的，即_____、_____和_____。 8．在LPS的分子中，存在有3种独特糖，它们是_____、____和____。 9．用人为方法除尽细胞壁的细菌称为____，未除尽细胞壁的细菌称为____，因在实验室中发生缺壁突变的细菌称为_____，而在自然界长期进化中形成的稳定性缺壁细菌则称为_____。 10．细胞质膜的主要功能有______、______、_____、______和______。 三、选择题： 1．G-细菌细胞壁的最内层成分是( )。 (1)磷脂(2)肽聚糖(3)脂蛋白(4)LPS 2．G+细菌细胞壁中不含有的成分是( )。 (1)类脂(2)磷壁酸(3)肽聚糖(4)蛋白质 3．肽聚糖种类的多样性主要反映在( )结构的多样性上。 (1)肽桥(2)黏肽(3)双糖单位(4)四肽尾 4．磷壁酸是( )细菌细胞壁上的主要成分。 (1)分枝杆菌(2)古生菌(3)G+ (4)G- 5．在G—细菌肽聚糖的四肽尾上，有一个与G+细菌不同的称作( )的氨基酸。 (1)赖氨酸(2)苏氨酸(3)二氨基庚二酸(4)丝氨酸 6．脂多糖(LPS)是G+细菌的内毒素，其毒性来自分子中的（)。 (1)阿比可糖(2)核心多糖(3)O特异侧链(4)类脂A 7．用人为的方法处理G—细菌的细胞壁后，可获得仍残留有部分细胞壁的称作( )的缺壁细菌。 (1)原生质体(2)支原体(3)球状体(4)L型细菌 8．异染粒是属于细菌的( )类贮藏物。 (1)磷源类(2)碳源类(3)能源类(4)氮源类 9．最常见的产芽孢的厌氧菌是( )。 (1)芽孢杆菌属(2)梭菌属(3)孢螺菌属(4)芽孢八叠球菌屑 10．在芽孢的各层结构中，含DPA—Ca量最高的层次是( )。 (1)孢外壁(2)芽孢衣(3)皮层(4)芽孢核心 四、判断题 1．古生菌也是一类原核生物。 2．G+细菌的细胞壁，不仅厚度比G-细菌的大，而且层次多、成分复杂。
怎样使用数字音频处理器现在数字音频处理器越来越多地运用到工程当中了，对于有基础有经验的人来说，处理器是一个很好用的工具，但是，对于一些经验比较欠缺的朋友来说，看着一台处理器，又是一大堆英文，不免有点无从下手。其实不用慌，我来介绍一下处理器使用步骤,以一个2进4出的处理器控制全频音箱＋超低音音箱的系统为例 1、首先是用处理器连接系统，先确定好哪个输出通道用来控制全频音箱，哪个输出通道用来控制超低音音箱，比如你用输出1、2通道控制超低音，用输出3、4通道控制全频。接好线了，就首先进入处理器的编辑（EDIT）界面来进行设置，进入编辑界面不同的产品的方法不同，具体怎么进入，去看说明书。 2、利用处理器的路由（ROUNT）功能来确定输出通道的信号来自哪个输入通道，比如你用立体声方式扩声形式，你可以选择输出通道1、3的信号来自输入A，输出通道的2、4的信号来自输入B。信号分配功能不同的产品所处的位置不同，有些是在分频模块里，有些是在增益控制模块里，这个根据说明书的指示去找。 3、根据音箱的技术特性或实际要求来对音箱的工作频段进行设置，也就是设置分频点。处理器上的分频模块一般用CROSSOVER或X-OVER表示，进入后有下限频率选择（HPF）和上限频率选择（LPF），还要滤波器模式和斜率的选择。首先先确定工作频段，比如超低音的频段是40－120赫兹，你就把超低音通道的HPF设置为40，LPF设置为120。全频音箱如果你要控制下限，就根据它的低音单元口径，设置它的HPF大约在50－100Hz,。处理器滤波器形式选择一般有三种，bessel,butterworth和linky-raily，我以前有帖子专门说明过三种滤波器的不同之处，这里不赘述。常用的是butterworth和linky-raily两种，然后是分频斜率的选择，一般你选24dB/oct就可以满足大部分的用途了。 4、这个时候你需要检查一下每个通道的初始电平是不是都在0dB位置，如果有不是0的，先把它们都调到0位置上，这个电平控制一般在GAIN功能里，DBX的处理器电平是在分频器里面的，用G表示。 5、现在就可以接通信号让系统先发出声音了，然后用极性相位仪检查一下音箱的极性是否统一，有不统一的，先检查一下线路有没有接反。如果线路没接反，而全频音箱和超低音的极性相反了，可以利用处理器输出通道的极性翻转功能（polarity或pol）把信号的极性反转，一般用Nomal或“＋”表示正极性，用INV或“－”表示负极性。 6、接下来就要借助SIA这类工具测量一下全频音箱和超低音的传输时间，一般来说是会有差异的，比如测到全频的传输时间是10ms，超低音是18ms，这个时候就要利用处理器的延时功能对全频进行延时，让全频和低音的传输时间相同。处理器的延时用DELAY或DLY表示，有些用m（米）有些用MS（毫秒）来显示延时量，SIA软件也同时提供了时间和距离的量，你可以选择你需要的数据值来进行延时 7、接下来就该进行均衡的调节了，可以配合测试工具也可以用耳朵来调，处理器的均衡用EQ来表示，一般都是参量均衡（PEQ），参量均衡有3个调节量，频率（F），带宽（Q 或OCT），增益（GAIN或G）。具体怎么调，就根据产品特性、房间特性和主观听觉来调了，这个就自己去想了。 8、均衡调好后，就要进行限幅器的设置了，处理器的限幅器用LIMIT来表示，进去以后一般有限幅电平（THRESHOLD），压缩比（RA TIO）的选项，你要做限幅就要先把压缩比RA TIO设置为无穷大（INF），然后配合功放来设置限幅电平，变成限幅器后，启动时间A TTACK和恢复时间RELEASE就不用去理了。DBX处理器的限幅器用PEAKSTOP来表示，启动后，直接设置限幅电平就可以了，至于怎么调限幅器，我有专门的帖子，自己去看。 9、都调好了就要保存数据，处理器的保存一般用STORE或SA VE表示，怎么存，就看产品说明书了。
一、选择题 1、下列选项不属于多媒体组成部分的是：（ C ）。 A、视频 B、声音 C、像素 D、文字 2、声波不能在( D )中传播。 A、水 B、空气 C、墙壁 D、中空 3、下列选项不属于声音的重要指标的是:( B )。 A、频率 B、音色 C、周期 D、振幅 4、下列选项表示波的高低幅度即声音的强弱的是：（ D ）。 A、频率 B、音色 C、周期 D、振幅 5、下列选项表示两个相邻的波之间的时间长度的是：（ C ）。 A、频率 B、音色 C、周期 D、振幅 6、下列选项表示每秒中振动的次数的是：（ A ）。 A、频率 B、音色 C、周期 D、振幅 7、自然界的声音是——信号，要使计算机能处理的音频信号必须将其——， 这种转换过程即声音的数字化。 (A/D) A. 连续变化的模拟离散化 B. 离散变化的模拟连续化 C. 连续变化的数字离散化 D. 离散变化的数字连续化 8、对声音信号进行数字化处理，是对声音因信号——。 (D) A. 先量化再采样 B. 仅采样 C. 仅量化 D. 先采样再量化 9、对声音信号进行数字化处理首先需要确定的两个问题是——。 (A) A. 采样频率和量化精度 B. 压缩和解压缩 C. 录音与播放 D. 模拟与压缩 10、对声音信号进行数字化时，间隔时间相等的采样称为——采样。 (B) A. 随机 B. 均匀 C. 选择 D. 模拟 11、对声音信号进行数字化时，用多少哥二进制位来存储表示数字化声音的 数据，称为——。 (D) A. 采样 B.采样频率 C.量化 D.量化精度 12、对声音信号进行数字化时，每秒钟需要采集多少个声音样本，称为——。 （B） A. 压缩 B. 采样频率 C. 解压缩 D. 量化精 13、乃奎斯特采样理论指出，采样频率不超过声音最高频率的（B）倍 A. 1 B. 2 C.3 D.4 14、满足奈奎斯特采样理论，则经过采样后的采样信号（A） A.可以还原成原来的声音 B.不能还原成原来的声音 Ｃ.是有损压缩 D.模拟声音 15、从听觉角度看，声音不具有（C）要素 A.音调 B.响度 C.音长 D.音色 16、声音的高低叫做（），他与频率（B） A.音调无关 B.音调成正比Ｃ.音调成反比Ｄ.响度无关 17、下列表示人耳对声音音质的感觉的是（C） A.音调 B.响度 C.音色 D.音量 18、从电话，广播中分辨出是熟人的根据（A）的不同，它是由谐音的多寡，各 谐音的特性决定的 A.音色 B.响度 C.频率 D.音调
第二章原核微生物 古菌（ａrcｈａea)在进化谱系上与细菌（bacteria）和真核生物相互并列,但其在细胞构造上却与细菌较为接近,同属于原核生物。原核微生物是指一大类细胞核无核膜包裹,只有称作核区(nｕcleaｒｒeｇioｎ)的裸露ＤNA的原始单细胞生物，包括细菌和古菌两大群。细菌的细胞膜含由酯键连接的脂类,细胞壁中含特有的肽聚糖（无壁的枝原体除外),DNA中一般没有内含子（但近年来也有例外的发现）。 2.１.1 细菌的定义 细菌是一类细胞细而短(０.５×0.5～５μm)、结构简单、细胞壁坚韧、以二等分裂方式繁殖和水生性较强的原核微生物。 2.1.2 细菌的形态 球状、杆状、螺旋状、三角形、方形、圆盘形等。 ２.1．3 细菌的构造 由于细菌的细胞极其微小（μｍ)又十分透明,因此用水浸片或悬滴观察法在光学显微镜下进行观察时,只能看到其大体形态和运动情况。若要在光学显微镜下观察其细致形态和主要构造,一般都要对它们进行染色。1884年丹麦医生C.Gｒam创立的革兰氏染色法（Ｇｒam stain）是最为重要的染色方法。 2.1.３.1 细菌的一般构造 一般细菌共有的结构：细胞壁、细胞膜、细胞质、核质体细胞最外层的一层厚实、坚韧的外被，有固定外形和保护细胞等多种功能。 通过结晶紫初染和碘液媒染后，在细胞膜内形成了不溶于水的结晶紫与碘的复合物（CVI ｄyｅcｏｍｐleｘ)。革兰氏阳性细菌由于其细胞壁较厚、肽聚糖网层次多和交联致密，故遇乙醇或丙酮作脱色处理时，因失水反而使网孔缩小，再加上它不含类脂,故乙醇处理不会溶出缝隙,因此能把结晶紫与碘复合物牢牢留在壁内，使其仍呈紫色。反之,革兰氏阴性细菌因其细胞壁薄、外膜层的类脂含量高、肽聚糖层薄和交联度差，在遇脱色剂后，以类脂为主的外膜迅速溶解,薄而松散的肽聚糖网不能阻挡结晶紫与碘复合物的溶出,因此，通过乙醇
数字语音实验 吕佩壕 10024134 一、实验要求 1.编程实现一句话语音的短时能量曲线，并比较窗长、窗口形状（以直 角窗和和哈明窗为例）对短时平均能量的影响 ； 2. 编程分析语音信号的短时谱特性，并比较窗长、窗口形状（以直角窗 和和哈明窗为例）对语音短时谱的影响 ； 3. 运用低通滤波器、中心削波和自相关技术估计一段男性和女性语音信 号的基音周期，画出基音轨迹曲线，给出估计准确率。 二、实验原理及实验结果 1.窗口的选择 通过对发声机理的认识，语音信号可以认为是短时平稳的。在5~50ms 的范围内，语音频谱特性和一些物理特性参数基本保持不变。我们将每个短时的语音称为一个分析帧。一般帧长取10~30ms 。我们采用一个长度有限的窗函数来截取语音信号形成分析帧。通常会采用矩形窗和汉明窗。图1.1给出了这两种窗函数在窗长N=50时的时域波形。 图1.1 矩形窗和hamming 窗的时域波形 矩形窗的定义：一个N 点的矩形窗函数定义为如下： {1,00,()n N w n ≤<=其他 Hamming 窗的定义：一个N 点的hamming 窗函数定义为如下： 0.540.46cos(2),010,()n n N N w n π-≤<-??? 其他 = 这两种窗函数都有低通特性，通过分析这两种窗的频率响应幅度特性可以发 0.2 0.40.60.811.2 1.41.61.82矩形窗 sample w （n ） 0.1 0.20.30.40.50.6 0.70.80.91hanming 窗 sample w （n ）
现（如图1.2）：矩形窗的主瓣宽度小（4*pi/N ），具有较高的频率分辨率，旁瓣峰值大（-13.3dB ），会导致泄漏现象；汉明窗的主瓣宽8*pi/N ，旁瓣峰值低（-42.7dB ），可以有效的克服泄漏现象，具有更平滑的低通特性。因此在语音频谱分析时常使用汉明窗，在计算短时能量和平均幅度时通常用矩形窗。表1.1对比了这两种窗函数的主瓣宽度和旁瓣峰值。 图1.2 矩形窗和Hamming 窗的频率响应 2．短时能量 由于语音信号的能量随时间变化，清音和浊音之间的能量差别相当显著。因此对语音的短时能量进行分析，可以描述语音的这种特征变化情况。定义短时能量为： 2 2 1 [()()] [()()]n n m m n N E x m w n m x m w n m ∞ =-∞ =-+= -= -∑∑ ，其中N 为窗长 特殊地，当采用矩形窗时，可简化为： 2 () n m E x m ∞ =-∞ = ∑ 图2.1和图2.2给出了不同矩形窗和hamming 窗长,对所录的语音“我是吕佩壕”的短时能量函数： （1）矩形窗（从上至下依次为“我是吕佩壕”波形图，窗长分别为32,64,128,256,512的矩形窗的短时能量函数）： 00.10.20.3 0.40.50.60.70.80.91 -80 -60-40-20 0矩形窗频率响应 归一化频率(f/fs)幅度/d B 00.10.20.3 0.40.50.60.70.80.91 -100 -50 Hamming 窗频率响应 归一化频率(f/fs) 幅度/d B
第二章原核微生物习 题及答案
第二章《原核微生物》习题 一、名词解释 1．细菌： 2．聚-β-羟丁酸(poly-β-hydroxybutyric acid，PHB ) 3．异染粒(metachromatic granules) 4．羧酶体(carboxysome) 5．芽孢(spore) 6．渗透调节皮层膨胀学说 7．伴孢晶体（parasporal crystal） 8．荚膜（capsule） 9．原核生物： 10．古生菌(archaea) 11．L型细菌 12．鞭毛(flagella) 13．富营养化(eutrophication)： 14．假肽聚糖 15．蓝细菌： 16．支原体。 17．立克次氏体 18．衣原体 二、填空题 1．证明细菌存在细胞壁的主要方法有，，和。 2．细菌细胞壁的主要功能为，，和等。 3．革兰氏阳性细菌细胞壁的主要成分为和，而革兰氏阳性细菌细胞壁的主要成分则是，，和。 4．肽聚糖单体是由和以糖苷键结合的，以及和 3种成分组成的，其中的糖苷键可被水解。 5．G+细菌细胞壁上磷壁酸的主要生理功能为，，和等几种。 6．G-细菌细胞外膜的构成成分为，，和。 7．脂多糖（LPS）是由3种成分组成的，即，和。 8．在LPS的分子中，存在有3种独特糖，它们是，和。 9．用人为方法除尽细胞壁的细菌称为，未除尽细胞壁的细菌称为，因在实验室中发生缺壁突变的细菌称为，而在自然界长期进化中形成的稳定性缺壁细菌则称为。 10．细胞质膜的主要功能有，，，和。 三、选择题 1．G细菌细胞壁的最内层成分是（）。 （1）磷脂；（2）肽聚糖；（3）脂蛋白；（4）LPS 2．G+细菌细胞壁中不含有的成分是（）。 （1）类脂；（2）磷壁酸；（3）肽聚糖；（4）蛋白蛋 3．肽聚糖种类的多样性主要反映在（）结构的多样性上。 （1）肽桥；（2）黏肽；（3）双糖单位；（4）四肽尾 4．磷壁酸是（）细菌细胞壁上的主要成分。 （1）分枝杆菌；（2）古生菌；（3）G+；（4）G- 5．在G-细菌肽聚糖的四肽尾上，有一个与G+细菌不同的称作（）的氨基酸。
数字音频处理器参数 Prepared on 24 November 2020
1. 扩声系统升级改造 （1）新增2台数字音频处理器。该处理器需要和原有视频会议系统、数字会议系统、讲台话筒、现场图传背包TVU系统、无线麦克风、控制室电脑、有线电视等信号源（原调音台连接图附件1图1所示）和新增录播系统进行音频集成，实现各系统音频信号的任意路由和控制。处理器具备12进8出，12路输入通道带AEC回声消除功能，拥有AVB网络接口，支持多达128X128AVB网络，具备 Speech Sense（语音触发技术）和 Sona AEC （回声消除技术）的新型处理算法，信号处理可通过软件直观的配置和控制，如：信号路由和混音、均衡、滤波、动态处理、延迟等。 （2）新增会场前后方音箱。在大厅前方选用2只柱状线列阵音箱，铰接列阵与线性列阵技术的结合，在大厅中后场两侧柱子上壁挂两只补声音箱，以满足中后场的声压级。 整个扩声系统改造后需要符合会场声学环境要求，声音清楚无回声，声音大小符合会场扩声需求。声学特性指标按中华人民共和国国家标准GB50371-2006《厅堂扩声系统设计规范》要求，列表如下： 2. 中控系统升级改造 新购一套中控系统，系统需具有双网卡功能，局域网端口用于连接主机到外部网络，ICSLAN端口连接AMX设备或其他第三方A/V设备使其独立于主要网络；同时支持IPv6和网络标准和特性；支持灵活的编程应用实现 （RPM,NetLinx和Java）；具有向后和跨平台的兼容性；具有自动诊断功能，能自动检测断线或连接错误的串口和红外端口；程序文件支持从USB驱动器导入/导出。 中控系统需要和原有及新增系统高度集成，将音频、视频、灯光、升降器、大屏控制等进行集中控制管理，能完成所有原系统控制部分的操作，支持一键式的模式切换，同时可支持此项目新购系统的统一控制。原中控系统连接示意图如下图所示： 3. 录播系统升级改造
第二章模拟音频和数字音频 人耳是声音的主要感觉器官，人们从自然界中获得的声音信号和通过传声器得到的声音电信号等在时间和幅度上都是连续变化的，时间上连续、而且幅度随时间连续变化的信号称为模拟信号(例如声波就是模拟信号，音响系统中传输的电流、电压信号也是模拟信号)，记录和重放信号的音源就是模拟音源，例如磁带／录音座、L P／L P电唱机等；时间和幅度上不连续或是离散的，只有0和l两种变化的信号称为数字信号，记录和重放数字信号的音源叫做数字音源，例如C D／C D机、D V D／D V D播放机等。究竟模拟音频与数字音频有什么不同呢?数字音频究竟有些什么优点呢?这些都是下面要介绍的。 模拟音频信号记录 录音泛指把声能转变为其他形式的能量而加以存储，录音时采用的存储媒介主要是磁性材料，如磁带、磁盘等，也可以是感光材料，如光盘等。由此录音技术也可分为磁记录和光记录两种。另外，近年来半导体内存件发展很快，成为一种新型的记录和存储设备。 在本节中将重点介绍磁带录音技术。 一、磁带录音装置的基本结构 磁带录音装置一般由磁头、机械传动(称为“机芯”)机构和电路三部分组成。 二、模拟录音载体---磁带 三、录音和放音的基本原理 1．消音原理 磁带在录音前，必须将原有的声音信号(剩磁)抹去，称之为消音或消磁。 2．录音与录音偏磁原理 录音是将声音电信号以剩磁的形式保存在磁带上。 3.放音原理 放音是将磁带上保存的剩磁信号还原成相应的声音电信号. 第二节数字音频基础 传统的信号都是以模拟手段进行处理的，称为模拟信号处理。所谓模拟音频是指用电信号(电压、电流)来模仿声音物理量的变化。因为声音是在时间和幅度上都连续变化的信号，所以模拟电信号在时间和幅度上也是连续变化的，故称之为模拟音频信号。 模拟音频信号处理有很多弊端，如抗干扰能力差，容易受机械振动、模拟电路的影响产生失真，远距离传输受环境影响较大等。 数字信号是以数字化形式对模拟信号进行处理，它在时间和幅度上都是离散的。 随着大规模集成电路以及计算机技术的飞速发展，加之数字信号处理理论和技术的成熟和完善，数字信号处理已逐渐取代了模拟信号处理。因为数字音频信号抗干扰性强， 无噪声积累可做到多代复制和长距离传输无失真! 数字音频信号的优点主要有以下几个方面： ①精度高：模拟信号处理的精度主要由元器件决定，很难达到0.001。而数字信号处理的精度主要决定于字长，14 位字长就可达到0.0001的精度。 ②灵活性高：数字信号处理系统的性能主要决定于乘法器的系数，而系数存放于内存中，因而只需改变存储的系 数就可得到不同的系统，比改变模拟系统方便得多。
云南大学软件学院 实验报告 序号：姓名：学号：指导教师：刘春花，刘宇成绩： 实验四数字音频处理 一、实验目的 1、熟悉并掌握MATLAB工具的使用； 2、实现音频文件的生成、读取、播放和转换的基本操作。 二、实验环境 MATLAB 6.5以上版本、WIN XP或WIN2000计算机 三、实验内容 1、用matlab 产生音乐。在matlab命令窗口执行下列命令，并回答问题 cf = 220; sf = 22050; d = 0.5; n = sf * d; t = (1:n)/sf; s0 = sin(2*pi*cf*t); sound(s0, sf); 1）信号的频率是多少? 采样频率是多少？采样间隔是多少？一共有
多少个采样点？声音有多少秒？ 频率:220 采样频率:22050 采样间隔: (1:n)/sf采样点: sin(2*pi*cf*t) 时长：0.5s 2）请解释sound(s, sf)函数的参数和实现的功能。如果把 sound(s0,sf)改为sound(s0,2*sf)听起来会有什么不同，为什么？时间更短,因为频率发生改变，变成了原来的2倍 3）执行sound1.m，听一听，能否在此程序基础上做修改，实现一小段音乐旋律，时间不少于10秒。并保存为为wav文件。 文件。获取相应参数，填空wav ）读取1、2． 执行语句： [B, fs, nbits]=wavread('C:\TEMP\hootie.wav'); % loads the clip size(B); % the size of B sound(B,fs) % plays the sound. 采样频率：44100
Biamp Nexia音频处理器介绍 编者案：传统扩音都是由调音台、音频处理、功放和音箱组成，设备众多，总投资不菲。而非专业音频的用户往往不会操作，刚调好的一个声场，几个月后已经是惨不忍睹。在数字化的今天，我们迎来数字媒体矩阵时代，调音台及各种音频处理设备被数字媒体矩阵取代，其计算机操作与集中控制联动，更加符合现代数字音视频集成工程应用的需要。 1.前言 Biamp Nexia 于1976年在美国俄勒冈州注册,最早是生产高品质的音乐器材,紧随着专业音频技术的发展,逐步转型生产专业音频处理设备。1996年生产出第一台Audia数字媒体矩阵，2003年推出智能话筒混音器、单声道/立体声线路混音器，功率放大器系列，同年推出专门针对中小型多媒体会议系统的NEXIA系列小型媒体矩阵(PM CS SP)。当远程会议走入人们视线时,Biamp也在2006年生产了专门针对远程会议的Nexia TC&VC.基于他们生产音乐器材的背景和对声音的热爱,他们对声音有很高的要求,同时也把这样的要求应用到所有产品中，而且把高品质声音作为产品生产的第一位。应用围很广,涉及政府、学校、公交、以及视频会议系统、体育场馆扩声工程，并享有很高的赞誉。在国际信息化产业联盟ICIA公布的最佳系统集成固定安装类产品大奖中,BIAMP公司的产品被权威期刊评为“最佳DSP处理大奖”。2003年进入中国市场，市场份额逐年上升; 你的远见可以成为现实
Nexia系列产品根据工程中遇到的现实问题而量身定做的。很多客户往往预算紧，但对声音质量的要求却毫不妥协，并且希望联网遥控。通过创新的数字信号处理技术，Nexia以小巧的外形提供了远胜于模拟系统的解决方案。 通过标配的Nexlink接口，最多可以4台Nexia设备级联成系统，彼此交换数字音频信号，并共享DSP资源。再配合VS8这样人性化的线控面板，一个灵活而实用的数字音频系统就展现在你的面前。高雅、简洁而且功能强大，在每天的日常实用中稳定地发挥效能。 Nexia软件：易于使用、精于设计。 界面直观、操作简单、功能强大，Nexia软件允许您以搭积木的方式进行系统设计。所有的设计操作都在同一个界面下完成，无需反复在不同页面间切换。令设计、修改，甚至推翻重来这一切工作都变得快捷而充满乐趣。为使工程项目进展更快，所有Nexia产品出厂时都包含了标准的音频系统设计，通电就能使用!如果您有特殊需求，也可以对工厂置的系统设计进行修改，实现您的梦想! 线控组件：人性外观，简洁有效。
物理化学习题三 《电化学》与《化学动力学》习题 一、选择题 1、 浓度为m的 Al2(SO4)3溶液中，正负离子的活度系数分别为,则平均活度 系数为（ ） A.（108）1/5m； B.（+2-3）1/5m ； C.（+2-3）1/5； D.（+3-2）1/5。 2、质量摩尔浓度为m的CuSO4水溶液，其离子平均活度与离子平均活度系数 及m之间的关系为 。 A. =· m B.= 41/4· m C.= 4· m D.= 21/4· m 3、电池反应(1)：2MnO4-+5SO32-+6H+==2Mn2++5SO42-+3H2O, 所对应电池的 电动势为E（1），Gibbs函数变为△r G m（1）；电池反应（2）：MnO4- +SO32-+3H+==Mn2++SO42-+H2O所对应电池的电动势为E（2），Gibbs函数变为△r G m（2）在相同的条件下，则（ ） A.△r G m（1）=△r G m（2），E（1）=E（2）； B.△r G m（1）=2△r G m（2）， E（1）=E（2）； C.△r G m（1）=△r G m（2），E（1）=2E（2）； D.△r G m（1）=2△r G m（2）， 2E（1）=E（2） 。 4、电解质溶液的摩尔电导率随溶液浓度的增加而 。 A. 减小 B.增大 C.先减小后增大 D.先增 大后减小 5、将AgNO3、CuCl2、FeCl3三种溶液用适当装置串联，通一定电量后，各阴 极上析出金属的 。 A. 质量相同 B. 物质的量相同 C. 还原的离子个数相同 D. 都不相同
6、在相距1m、电极面积为1m2的两电极之间和在相距10m、电极面积为 0.1m2的两电极之间，分别放入相同浓度的同种电解质溶液，则二者 。 A. 电导率相同，电导相同； B. 电导率不相同，电导相同； C. 电导率相同，电导不相同； D. 电导率不相同，电导也不相 同。 7、有甲、乙两电池如下，其电势关系为 。 甲:Pt，H2 (pθ)│HCl(0.01M)║HCl(0.1M)│H2(pθ)，Pt 乙:Pt，H2(pθ)│HCl(0.01M) │ Cl2 (pθ)- Cl2(pθ)│HCl(0.1M)│H2(pθ),Pt A. E甲 = 0.5E乙 B. E甲 = E乙 C. E甲 =2 E乙 D. E = 4E乙 甲 8、某电池可以写成如下两种形式： 甲：1/2 H2 ( pθ) + AgI (s)→ Ag (s) + HI (a) 乙： H2 ( pθ) + 2AgI (s)→ 2Ag (s) + 2HI (a) 则 。 A. E甲 = E乙，K甲 =K乙 B. E甲 ≠ E乙，K甲 =K乙 C. E甲 = E乙，K甲≠ K乙 D. E甲 ≠ E乙，K甲 ≠ K乙 9、电池 （1）Cu (s)│Cu+(a Cu+)║Cu+ (a Cu+)，Cu2+ (a Cu2+)│Pt (s) （2）Cu (s)│Cu2+(a Cu2+)║Cu+(a Cu+)，Cu2+(a 2+)│Pt (s) Cu 的反应均可写成Cu (s) + Cu2+ (a Cu2+) 2Cu+(a Cu+)，此两电 池的标准电池电动势Eθ及电池反应的标准Gibbs自由能变化Δr Gθ 的关系为 。 A. Δr Gθ，Eθ均相同 B. Δr Gθ相同，Eθ不同 C. Δr Gθ不同，Eθ相同 D. Δr Gθ， Eθ均不同 10、298K时电池Pt (s) │H2 ( pθ)│HCl (m)│H2 ( 0.1pθ) │Pt (s) 的电池电动势为 。 A. 0.118V B. ?0.059V C. 0.0295V D. ?0.0295V
数字语音实验 吕佩壕10024134 一、实验要求 1. 编程实现一句话语音的短时能量曲线，并比较窗长、窗口形状（以直 角 窗和和哈明窗为例）对短时平均能量的影响 ； 2. 编程分析语音信号的短时谱特性，并比较窗长、窗口形状（以直角窗 和 和哈明窗为例）对语音短时谱的影响 ； 3. 运用低通滤波器、中心削波和自相关技术估计一段男性和女性语音信 号 的基音周期，画出基音轨迹曲线，给出估计准确率。 二、实验原理及实验结果 1.窗口的选择 通过对发声机理的认识，语音信号可以认为是短时平稳的。在 5~50ms 的范 围内，语音频谱特性和一些物理特性参数基本保持不变。我们将每个短时的语音 称为一个分析帧。一般帧长取10~30ms 我们采用一个长度有限的窗函数来截取 语音信号形成分析帧。通常会采用矩形窗和汉明窗。图1.1给出了这两种窗函数 在窗长N=50时的时域波形。 图1.1矩形窗和hamming 窗的时域波形 矩形窗的定义：一个N 点的 矩形窗函数定义为如下： 1,0 n N w （n ） °,其他 0.54 0.46cos(2 w(n)= 0,其他 这两种窗函数都有低通特性，通过分析这两种窗的频率响应幅度特性可以发 2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 Hammi ng S 的定义：一个 N 点的hamming 窗函数定义为如下: "),0 矩 形 窗 sample n hanming 0.9 0.8 0.7 0.5 0.4 0.3 0.2 0.1 sample 0.6
现(如图1.2 ):矩形窗的主瓣宽度小(4*pi/N ),具有较高的频率分辨率，旁瓣 峰值大(-13.3dB )，会导致泄漏现象；汉明窗的主瓣宽 8*pi/N ，旁瓣峰值低 (-42.7dB )，可以有效的克服泄漏现象，具有更平滑的低通特性。因此在语音频 谱分析时常使用汉明窗，在计算短时能量和平均幅度时通常用矩形窗。表 1.1 对比了这两种窗函数的主瓣宽度和旁瓣峰值。 2 .短时能量 由于语音信号的能量随时间变化，清音和浊音之间的能量差别相当显著。 因 此对语 音的短时能量进行分析，可以描述语音的这种特征变化情况。定义短时能 量为： n 2 2 E n [x(m)w (n m)] [x(m)w (n m)] m m n N 1 ，其中N 为窗长 特殊地，当采用矩形窗时，可简化为： E n x 2(m) m 图2.1和图2.2给出了不同矩形窗和hamming 窗长,对所录的语音“我是吕 佩壕”的短时能量函数： (1)矩形窗(从上至下依次为“我是吕佩壕” 波形图，窗长分别为 32,64,128,256,512的矩形窗的短时能量函数)： 7 E L ■ U r ■ | If V n 1 fb f 、 U v 1 - f \f J V ii 1 f - ! 1 ■ if V '1 ■ 9 i ? y\p 1- 度 幅 矩形窗频率响应 归一化频率(f/fs) Hamming 窗频率响应 -50 -100 0.2 0.3 0.7 0.8 0.9 0.4 0.5 0.6 归一化频率(f/fs) 图1.2 矩形窗和Hamming 窗的频率响应 0.1
第二章原核微生物 一、名词解释 1、荚膜：一些细菌在其细胞表面分泌的、把细胞壁完全包围封住的一种粘性物质，一般成分为多糖，少数为多肽或多糖与多肽的复合物。荚膜具有保护、贮藏、附着和堆积代谢废物等生理功能。 2、芽孢：某些细菌在它的生活史中的某个阶段或某些细菌遇到不良环境时，在其细胞内形成的一个 圆形或椭圆形、厚壁、含水量低、抗逆（抗热、抗药物、抗辐射等）极强的内生休眠孢 子。产芽孢的细菌主要有好氧的芽孢杆菌属和厌氧的梭菌属。 3、鞭毛：由细胞质膜上的鞭毛基粒长出的穿过细胞壁神像体外的一条纤细的波浪状的丝状物。 4、菌落：由一个细菌繁殖起来的，由无数细菌组成具有一定形态特征的细菌集团。 5、菌苔：细菌在斜面培养基接种线上长成的一片密集的细菌群落。 6、丝状菌：细菌的一种形态，分布在水生境、潮湿土壤和活性污泥中，由柱状或椭圆状的细菌细胞 连接在一起，外围有鞘。如铁细菌，丝状硫细菌等。 7、菌胶团：有些细菌由于其遗传特性决定，细菌之间按一定的排列方式互相黏集在一起，被一个公 共荚膜包围形成一定形状的细菌集团叫菌胶团。 8、衣鞘：球衣菌属、纤发菌属、发硫菌属、亮发菌属、泉发菌属等丝状体表面的粘液层或荚膜硬质化，形成一个透明坚韧的空壳，叫衣鞘。 9、黏液层：有些细菌的表面分泌的黏性的疏松地附着在细菌细胞壁表面上的，与外界没有明显边缘 的多糖。 二、选择题 1.革兰氏阴性菌细胞壁的⑤成分比阳性菌高。 ①肽聚糖②磷壁酸 ③类脂质④蛋白质⑤类脂质和蛋白质 2. ②可作为噬菌体的特异性吸附受体，且能贮藏磷因素。 ①脂多糖②磷壁酸③质膜④葡聚糖 3. 噬菌体属于病毒类别中的①。 ①微生物病毒②昆虫病毒③植物病毒④动物病毒 4. 下列微生物中，属于革兰氏阴性菌的是①。 ①大肠杆菌②金黄色葡萄球菌③芽孢杆菌④枯草杆菌 5. 革兰氏阳性菌对青霉素②。 ①不敏感②敏感③无法判断