Plant Pathologhy

  1. abiotic
    pertaining to the absence of life, as diseases not caused by living organisms
  2. drought
    insufficient soil water for normal plant growth
  3. sunscald or sunburn
    injury of plant tissues burned or scorched by direct sun or or sunburn
  4. mechanical injury
    injury of a plant part by abrasion, mutilation, or wounding
  5. lodge
    to fall over
  6. macronutrient
    • an element needed in relatively large quantities for plant growth, e.g.
    • nitrogen (N), phosphorus (P), and potassium (K); (see micronutrient)
  7. micronutrient
    an essential element needed by plants for growth and required in very small amounts (see macronutrient)
  8. pollination
    transfer of pollen from anther to stigma or from a staminate cone to an ovulate cone
  9. air pollution
    any air contaminant that causes undesirable effects on living organisms or materials
  10. secondary pollutant
    • air pollutant that must be chemically produced from other air pollutants,
    • e.g. ozone (O3) that is a product of a photochemical reaction
    • of exhaust products from combustion engines in the atmosphere
  11. photochemical reactions
    chemical reactions that require sunlight
  12. acute
    pertaining to symptoms that develop suddenly(see chronic)
  13. chronic
    pertaining to slow-developing, persistent, or recurring symptoms (see acute)
  14. peroxyacetal nitrates (PAN)
    • a secondary air pollutant formed when the exhaust of automobiles and
    • other internal combustion engines is in the presence of sunlight
  15. sulfur dioxide (SO2)
    • a primary air pollutant produced in industrial processes and coal
    • burning that causes interveinal necrosis on broadleaf plants and tip
    • necrosis on conifers
  16. nitrogen oxides
    primary air pollutants produced from internal combustion engines and other industrial processes
  17. primary pollutant
    • air pollutant that is released directly into the atmosphere and is
    • harmful to plants, e.g. SO2 or NOx
  18. acid precipitation
    • precipitation (fog, rain, snow) with a low pH, due to the presence of
    • nitric and sulfuric acid formed by the reaction of air pollutants (N0x and S02) with water
  19. forest decline
    • combination of biotic factors (e.g. insect pests, pathogens) and
    • abiotic factors (e.g. drought, air pollution) that contributes to poor
    • growth and death of populations of trees
  20. ethylene
    a plant hormone influencing various aspects of vegetative growth, fruit ripening, abscission of plant parts,and the senescence of flowers
  21. hydrogen fluoride (HF)
    • a common pollutant from volcanoes and several industries such as brick
    • factories, aluminum smelters, and phosphate fertilizer factories.
  22. herbicide
    a chemical used for killing plants or inhibiting plant growth, e.g. a weed or grass killer
  23. drift (of pesticides)
    movement of airborne particles of a spray, dust, or vapor away from the target area during or shortly after an application
  24. symptom
    indication of disease by reaction of the host, e.g. canker, leaf spot, wilt (see sign)
  25. temporary wilt
    wilt due to insufficient soil water from which a plant can recover when water is supplied
  26. scorch
    any symptom that suggests the action of flame or fire on the affected part, often seen at the margins of leaves
  27. etiolation
    elongation of stems caused by reduced light intensities
  28. winterburn
    foliar necrosis, often marginal, of plants that retain their leaves in winter due to water deficiency because they cannot take up water from frozen soils
  29. diagnostic
    a distinguishing characteristic important for the identification of a disease or other condition
  30. necrosis
    death of cells or tissue, usually accompanied by black or brown darkening
  31. damping-off
    death of a seedling before or shortly after emergence due to decomposition of the root and/or lower stem; it is common to distinguish between preemergence damping-off and postemergence damping-off
  32. chemotaxis
    movement or growth of an organism in response to changing concentration of a chemical stimulus, often in relation to food or for mating chemotherapy
  33. leaf spot
    a plant disease lesion typically restricted in development in the leaf after reaching a characteristic size
  34. blotch
    necrotic area of tissue irregular in form
  35. blight
    sudden, severe, and extensive spotting, discoloration, wilting, or destruction of leaves, flowers, stems, or entire plants
  36. needle cast
    disease symptom caused by fungi resulting in premature drop of needles
  37. bacterial streaming
    large populations of bacteria that exude from the cut surface of infected plant tissue when observed with a microscope
  38. acervulus
    erumpent, cushionlike fruiting body bearing conidiophores, conidia, and sometimes setae
  39. conidium
    an asexual, nonmotile fungal spore that develops externally or is liberated from the cell that formed it
  40. mosaic
    disease symptom characterized by non-uniform coloration, with intermingled normal, light green and yellowish patches, usually caused by a virus; often used interchangeably with mottle
  41. mottle
    disease symptom comprising light and dark areas in an irregular pattern,usually caused by a virus; often used interchangeably with mosaic
  42. ringspot
    disease symptom characterized by yellowish or necrotic rings enclosing green tissue, as in some plant diseases caused by viruses
  43. vein banding
    symptom of virus disease in which regions along veins are darker green than tissue between veins
  44. powdery mildew
    a white, powdery, superficial ascomycetous fungus that is an obligate parasite and generally is found only on one or a few closely related species of plants
  45. downy mildew
    a plant disease in which the fungus appears as a downy growth on the host surface; caused by a member of the oomycetes
  46. biotroph
    an organism that can live and multiply only on another living organism (see necrotroph)
  47. ascospore
    sexual spore borne in an ascus
  48. sporangiospore
    non-motile, asexual spore that is borne in a sporangium
  49. sporangium
    saclike fungal structure in which the entire contents are converted into an indefinite number of asexual spores
  50. rust
    a disease caused by a specialized group of basidiomycetes that often produces spores of a rusty color
  51. alternate host
    one of two kinds of plant on which a parasitic fungus (e.g. rust) must develop to complete its life cycle
  52. macrocyclic
    a rust fungus that typically exhibits all five stages of the rust life cycle (see demicyclic, microcyclic)
  53. demicyclic
    a rust fungus that lacks the urediniospore (repeating) stage (e.g. many species of Gymnosporangium) (see macrocyclic, microcyclic)
  54. microcyclic
    describing a rust fungus that produces only teliospores and basidiospores (see demicyclic, macrocyclic)
  55. autoecious
    in reference to rust fungi, producing all spore forms on one species of host plant (see heteroecious)
  56. white rust
    common name usually used for diseases caused by oomycetes in the genus Albugo
  57. smut
    a disease caused by a smut fungus (Ustilaginales) in the Basidiomycota or the fungus itself; it is characterized by masses of dark brown or black, dusty to greasy masses of teliospores that generally accumulate in black, powdery sori
  58. vascular wilt disease
    a xylem disease that disrupts normal uptake of water and minerals, resulting in wilting and yellowing of foliage
  59. flag
    isolated, wilted or necrotic branch with dead leaves attached
  60. fastidious
    in reference to prokaryotic organisms, having special growth and nutritional requirements
  61. phytoplasma
    plant-parasitic pleomorphic mollicute (prokaryote with no cell wall) found in phloem tissue; cannot yet be grown on artificial nutrient media
  62. canker
    a plant disease characterized (in woody plants) by the death of cambium tissue and loss and/or malformation of bark, or (in non-woody plants) by the formation of sharply delineated, dry, necrotic, localized lesions on the stem; "canker" may also be used to refer to the lesion itself, particularly in woody plants
  63. girdle
    to circle and cut through a stem or the bark and outer few rings of wood, disrupting the phloem and xylem
  64. gall
    abnormal swelling or localized outgrowth, often roughly spherical, produced by a plant as a result of attack by a fungus, bacterium, nematode, insect, or other organism
  65. hypertrophy
    abnormal increase in the size of cells in a tissue or organ, often resulting in the formation of galls or tumors
  66. hyperplasia
    abnormal increase in the number of cells, often resulting in the formation of galls or tumors
  67. plasmid
    a circular, self-replicating hereditary element that is not part of a chromosome; plasmids are used in recombinant DNA experiments as acceptors and vectors of foreign DNA
  68. ectotrophic
    fungal development primarily over the root surface
  69. white rot
    type of wood decay resulting from enzymatic action of fungi; it degrades all components of wood, including lignin, leaving the wood light-colored and spongy
  70. brown rot
    wood decay resulting from selective removal of cellulose and hemicellulose, leaving a brown amorphous residue that usually cracks into cubical blocks and consists largely of slightly modified lignin
  71. mycotoxin
    poisonous compound produced by a fungus
  72. aflatoxin
    chemical byproduct from Aspergillus flavus and A. parasiticus harmful to humans and other animals
  73. sclerotium
    a vegetative resting body of a fungus, composed of a compact mass of hyphae with or without host tissue, usually with a darkened rind
  74. infected
    process in which an organism enters, invades, or penetrates and establishes a parasitic relationship with a host plant
  75. infested
    to attack as a pest (used especially of insects and nematodes); to contaminate, as with microorganisms; to be present in large numbers
  76. soil inhabitant
    an organism that maintains its population in soil over a period of time
  77. soil invader
    an organism whose population in soil diminishes in several months to years
  78. infection court
    site in or on a host plant where infection can occur
  79. stoma
    structure composed of two guard cells and the opening between them in the epidermis of a leaf or stem, functioning in gas exchange
  80. hydathode
    epidermal leaf structure specialized for secretion or exudation of water; leaf opening at terminus of vein
  81. lenticel
    a natural opening in the surface of a stem or tuber, fruit or root for gas exchange
  82. wounds
    injuries to plant tissues that often breach barriers (cuticle, bark, cell walls) that might otherwise exclude pathogens; some pathogens (e.g. viruses) can enter plants only through a wound; wounds may occur from natural growth processes, physical and chemical agents, animals (especially insects), and many human agricultural activities, such as pruning
  83. phylloplane
    leaf surface
  84. boundary layer
    the calm layer of air on surfaces below the layer of more turbulent air
  85. rhizosphere
    microenvironment in the soil, immediately around plant roots
  86. soil pasteurization
    process used to free soil of selected harmful microorganisms using heat
  87. vector
    a living organism (e.g., insect, mite, bird, higher animal, nematode, parasitic plant, human) able to carry and transmit a pathogen and disseminate disease; (in genetic engineering) a vector or cloning vehicle is a self-replicating DNA molecule, such as a plasmid or virus, used to introduce a fragment of foreign DNA into a host cell
  88. degree-day
    the departure of the average daily temperature from a defined base (e.g.the minimum recognized temperature for the growth of a plant species). The number of degree-days may be totaled to assess the accumulated warmth of a particular year's growing season.
  89. fungistasis
    inhibition of fungal growth, sporulation, or spore germination but not death; used to describe the nonspecific phenomenon in natural soils where spore germination is inhibited and often overcome by rhizosphere nutrients
  90. appressorium
    swollen, flattened portion of a fungal filament that adheres to the surface of a higher plant, providing anchorage for invasion by a fungus
  91. penetration peg
    the specialized, narrow, hyphal strand on the underside of an appressorium that penetrates host cells
  92. infection peg
    the specialized, narrow, hyphal strand on the underside of an appressorium that penetrates host cells
  93. hyphopodium
    stalked, thick-walled, lobed cells that stick to plant surfaces; sometimes used to describe the infection structures produced by ectotrophic hyphae of certain root-infecting fungi such as Gaeumannomyces (take-all pathogen)
  94. haustorium
    specialized branch of a parasite formed inside host cells to absorb nutrients
  95. direct penetration
    penetration of plant tissues by a pathogen through barriers such as leaf cuticle by chemical and physical means (e.g. penetration peg)
  96. indirect penetration
    penetration of plant tissues by a pathogen through natural openings (e.g. stomata) or wounds
  97. incubation period
    the time between penetration of a host by a pathogen and the first appearance of disease symptoms; the time during which microorganisms inoculated onto a medium are allowed to grow
  98. latent period
    the time between infection and the production of new inoculum; the time after a vector has acquired a pathogen and before it can be transmitted
  99. enzyme
    protein that catalyzes a specific biochemical reaction
  100. extracellular
    outside a cell
  101. cellulose
    carbohydrate polysaccharide composed of glucose units; major component of plant primary cell wall
  102. pectin
    a methylated polymer of galacturonic acid found in the middle lamella and the primary cell wall of plants; jelly-forming substance found in fruit
  103. growth regulator
    a chemical substance produced in one part of an organism and transported in minute quantities to induce a growth response in another part, e.g. in plants, auxins, cytokinins, and gibberellins
  104. auxin
    plant hormone (growth regulator) influencing growth through cell elongation
  105. cytokinins
    plant hormones (growth regulators) that control cell division and are important for shoot stimulation of callus in tissue culture
  106. gibberellins
    plant hormones (growth regulators) that affect stem elongation
  107. ethylene
    a plant hormone influencing various aspects of vegetative growth, fruit ripening, abscission of plant parts, and the senescence of flowers
  108. abscission
    the shedding of leaves or other plant parts as the result of physical weakness in a specialized layer of cells (the abscission layer) that develops at the base of the structure
  109. secondary metabolite
    a compound produced in microbes (e.g., mycotoxins, syringomycins) or plants (e.g., caffeine or nicotine) that is not necessary for normal growth and development
  110. induced
    produced in response to a stimulus
  111. papilla
    nipple-like projection; used to describe the tip of some sporangia and the localized wall thickenings on the inner surface of plant cell walls at sites penetrated by fungi
  112. callose
    amorphous, hardened carbohydrate constituent of plant cell walls, commonly developing upon injury
  113. tylosis
    balloonlike extrusions of parenchyma cells into lumina of contiguous vessels that partially or completely block them
  114. gum
    gelatinous, sugary aggregate that is synthesized and exuded by plant tissues
  115. cork
    external protective tissue of a stem or root, impermeable to water and gasses; the primary component of bark
  116. shot-hole
    symptom in which small lesions fall out of leaves, giving the leaf the appearance of being hit by buckshot
  117. phytoalexin
    substance produced in higher plants in response to a number of chemical,physical, and biological stimuli that inhibits the growth of certain micro-organisms
  118. hypersensitive response
    rapid and localized cell death at the site of infection in resistant interactions between plants and pathogens
  119. induced systemic resistanc
    reduced disease symptoms on a portion of a plant distant from the area where the inducing agent is active, caused by the triggering of active plant defenses against a variety of pathogens; used to describe increased resistance in plants induced by certain rhizobacteria
  120. elicitor
    a molecule produced by the host (or pathogen) that induces a response by the pathogen (or host)
  121. resistant
    possessing properties that prevent or impede disease development (see susceptible)
  122. susceptible
    prone to develop disease when infected by a pathogen (see resistance)
  123. virulence
    degree or measure of pathogenicity; relative capacity to cause disease
  124. gene-for-gene hypothesis
    the hypothesis that corresponding genes for resistance and virulence exist in the host and pathogen, respectively
  125. specific resistance
    resistance which is effective against some biotypes or races of the pathogen, but not others, usually inherited monogenically and expressed qualitatively.
  126. monogenic
    determined by a single gene
  127. vertical resistance
    resistance which is effective against some biotypes or races of the pathogen, but not others, usually inherited monogenically and expressed qualitatively
  128. horizontal resistance
    resistance which is effective against all biotypes of the pathogen
  129. cross-protection
    the process whereby a normally susceptible host is infected with a less virulent pathogen (usually a virus) and thereby becomes resistant to infection by a second, usually related, more virulent pathogen
  130. protoplast
    living cell exclusive of a wall
  131. biotechnology
    the development of genetically modified organisms through the use of modern technology and processes, including genetic engineering
  132. genetically modified organism; (GMO)
    organism possessing a gene from another species; used to describe the organisms that have been the subject of genetic engineering
Card Set
Plant Pathologhy
Ch. 7,8,9