Pl Sc 352 Final

  1. concerns about invasive species invading an area? (3)
    • alter soil/water quality
    • alter our experience of nature in a negative way
    • recent global change (like climate change) increase volatility of species movements
  2. 3 theories of why species that are non-invasive in their natural habitat can become invasive in areas where they are introduced?
    • 1. enemy release hypothesis
    • 2. novel weapons
    • 3. evolution of increased competitive ability
  3. enemy release hypothesis
    • some invasions may be caused by the lack of certain herbivore pests
    • introduced species are released from the regulatory pressures of specialized enemies in their natural range
  4. introduced species often lack original _______
  5. why might introduced species have fewer symbionts?
    • "missing the boat"
    • "drowning upon arrival"
    • "lagging behind"
  6. evolution of increased competitive ability
    introduced species spend energy and resources on defence mechanisms meant to deter specialized enemies in natural range, if new range doesn't have these enemies, defence mechanisms may be selected against and energy and resources may be budgeted for growth and competition
  7. novel weapons hypothesis
    plants produce and exude many compounds that help with different survival methods, NWH says that species may exude novel compounds that affect the native plants/soil biota somehow causing a fitness increase for the introduced plant
  8. invasive alien plants definition
    • vascular plants recently introduced to Canada
    • history of invasiveness and/or weediness in other parts of its range
    • potential to establish proliferate, spread, and cause broadly defined detrimental consequences in ecosystems
  9. percentages of introduced and native plants in Canada?
    • 25% introduced
    • 75% native
  10. prevention of introduction of alien species (4)
    • block at or before entry into canada
    • weed risk assessments 
    • border control
    • prohibited noxious weed list
  11. weed risk assessment: trait-based (5)
    • fecundity
    • dormancy
    • seed dispersal
    • climatic matching
    • expert opinion
  12. 6 stages of invasion process
    • transport
    • introduction
    • colonization
    • naturalization
    • spread (exponential growth phase)
    • impact
  13. examples of invasive plants in canada of concern on the plains
    • reed canary grass
    • crested wheat grass
    • downy brome
    • leafy spurge
    • toadflax
  14. invasive plants of national concern (canada)
    • purple loosestrife
    • canada thistle
    • hawkweeds
    • smooth brome grass
  15. what 3 factors make a habitat invasible?
    • disturbance (humans increase disturbance)
    • diversity (more diversity = more durable community)
    • resource availability (more resources left over than used, invasiveness increases)
  16. 3 areas involved in simplified invasion theory
    • propagule pressure
    • biotic factors
    • abiotic factors
  17. 3 ways that tillage and cultivation influence weeds
    • uproot, dismember, bury growing weeds and dormant perennial roots and rhizomes
    • change the soil environment in ways that can promote germination and establishment, or less commonly inhibit germination 
    • move weed seeds and propagules vertically and horizontally
  18. 4 factors in weed seed germination
    • N levels
    • O2
    • light
    • temperature
  19. ______ relative to how ____ in soil profile it is can affect germination
    seed size, deep
  20. deep rooted perennials are controlled by _____ of _____ reserves
    exhaustion, root
  21. stale seed bed process
    • tillage, pause, tillage, seeding
    • stimulates germination of weed seeds
    • has increased energy costs and delays time of seeding
  22. alternative early seeding
    • gets crop up early so its most competitive, gets the most growing degree days 
    • works better for more competitive crops that can close the canopy quickly
  23. cons of tillage
    • makes soil more susceptible to wind and water erosion
    • dries soil
    • decreases soil tilth
    • decreases soil OM thru oxidation and enhanced soil microbial activity
    • reduces soil water infiltration rates
  24. conventional seeding
    uses multiple tillage passes (fall, spring) prior to seeding
  25. reduced tillage
    reduction of some of the tillage passes (usually fall the first to be removed)
  26. direct (no-till) seeding
    seeding and fertilizing is completed in a single operation, no additional tillage
  27. seed bed utilization
    the spread of the seed as a % of the total area
  28. seeding difficulties caused by high crop reside levels (direct seeding)
    • hair pinning
    • reduced seed/soil contact
  29. how does direct seeding reduce weed seed germination?
    • reduction in aeration
    • reduced nitrogen release
    • reduced light stimulation
  30. control methods include methods that:
    • surpress weed growth
    • prevent/surpress
    • reduce seed reserves in soil
    • prevent/reduce weed spread
  31. 5 generally recognized methods of weed control
    • prevention (sanitation + containment)
    • mechanical
    • biological
    • chemical
    • cultural
  32. certified seed
    has certificate analysis outlining species and number of weed seeds present, doesn't mean weed free
  33. tolerance for prohibited noxious weed seed in any pedigreed seed?
    zero tolerance
  34. Seeds Act vs. Weed Control Act
    • Seeds Act: federal
    • Weed Control Act: provincial
  35. Weed prevention practices
    • weed free crop seed
    • weed free manure/compost
    • clean equipment
    • eliminate weeds near irrigation/edges
    • patch control
    • scouting necessary to ID new weeds
  36. contact herbicide
    herbicide that isn't translocated, kills what it touches
  37. systemic herbicide
    one that moves in the plant xylem and phloem, affects more tissue and acts more slowly
  38. selective herbicide
    controls some plants with reduced effect on other plants
  39. non-selective herbicide
    controls all plants
  40. time of application
    preplant, in crop, post harvest, post-plant, pre-emergence
  41. herbicide sites of action
    • proteins, usually enzymes
    • not all sites in the plant are suitable herbicide sites
  42. Group
    group of herbicides which affect a particular target site
  43. How do herbicides kill plants? 5 steps
    • 1. penetrate through waxy leaf or root hair
    • 2. move through watery space around the cell (apoplast)
    • 3. enter cell by passing through an oily membrane (plasmadesmata)
    • 4. reach target site
    • 5. inhibit the target
  44. uptake and translocation of herbicide affected by (3 things)
    • the physiochemical properties of the herbicide
    • weed biology (ex. surface of plant, whether leaf is waxy/hairy/etc)
    • environmental factors prior to and following application
  45. apoplast
    water interior of the plant, non-living
  46. symplast
    living part of the plant enclosed in the PM
  47. KOW
    • octanol-water partition coefficient
    • ratio of a chemical's concentration in the octanol phase to its concentration in the aqueous phase
  48. chemicals with low KOW values ...
    • .. less than 10
    • are considered pretty hydrophillic, tend to have high water solubilities
  49. chemicals with high KOW values...
    • ... ex. over 104
    • are very hydrophobic
  50. primary movement of herbicides?
    simple diffusion/concentration
  51. proton pump
    • protein in the membrane that maintains a protein gradient bw the inside and outside of the cell
    • energy required
  52. weak acid trapping
    • allows for concentration of herbicide within a cell or organelle against a concentration gradient
    • weak acid herbicides are trapped inside cells
  53. dissociation constant
    • pKa
    • describes a product's weak acid nature
    • pH of the solution where equal parts of the herbicide is associated and dissociated 
    • this equilibrium state is at pKa ~ 2.0-4.0
  54. xylem translocatin
    • one way transport from roots to leaves
    • herbicides that are very water soluble and not acid trapped can get swept along in the xylem stream
    • generally deposited in the outside edges of leaves
    • KOW <10 
    • pKA ~ 4??
  55. phloem translocation
    • herbicides move in phloem toward the sink for sugars
    • sinks vary with time of year
    • herbicide that is acid trapped can be translocated in phloem
    • bi-directional
  56. Group 9 herbicides
  57. Group 9 pKa and Kow
    • Kow= 0.0006-0.0017
    • pKa= 2.6, 5.6, 10.3
  58. group 9 application and translocation
    • foliar application
    • moves in the phloem, is a weak acid so can be weak acid trapped
  59. group 9 site of action
  60. where in the plant does group 9 herbicide work?
    enzyme in the shikimate pathway, in the chloroplast
  61. metabolism of group 9 herbicides
    • blocks EPSPS, shikimate and shikimate-3 build up to high amounts
    • carbon flow is disrupted and messes up sucrose pathway, because most of the carbon is turned into shikimate
  62. target species of group 9
    • non-selective herbicide
    • kills both broadleaves and grasses
  63. group 9 toxicity to humans
    none really
  64. group 9 soil residual activity
  65. herbicide resistance to group 9?
  66. Group 1 herbicides
    • ACCase inhibitors
    • affect lipid biosynthesis
  67. group 1 pKa and Kow
    • weak acid and lipophillic
    • pKa=2.9-4.5
  68. group 1 uptake and translocation
    • moves in phloem
    • lipophillic herbicide enters cuticle v quickly but takes a while to get through watery cell layer
  69. group 1 site of action
    • enzyme ACCase
    • meristems
  70. where in the plant does group 1 herbicide affect?
  71. group 1 metabolism
    • FOPS applied as pro-herbicides (inactive form)
    • DIMS and DENS applied as active molecules
  72. group 1 target species
  73. symptoms of group 1
    • pulling out of leaf
    • chlorosis
    • pinching off at base of stems
  74. group 1 soil residual activity
    generally none under typical use patterns
  75. group 1 herbicide resistance
    metabolic resistance and target site resistance types
  76. group 1 antagonism?
    can be antagonized by auxinic herbicides
  77. group 1 safeners?
    • yes, can be used to protect grass crops from herbicide activity
    • GSTs and P450s
  78. group 2 herbicides
    ALS inhibitors
  79. group 2 Kow and pKa
    all weak acids, pretty water soluble
  80. group 2 uptake and translocation
    • enter by passive diffusion
    • trapped in cell by weak acid trapping
    • translocation: moves in phloem
  81. group 2 site of action
    meristem: binds to ALS to block channel for protein production
  82. where in plant does group 2 affect
  83. group 2 metabolism
    • selectivity based on how different plants can break down herbicide
    • crops metabolize it, weeds don't
  84. group 2 target species
    affects grasses and broadleaf weeds
  85. group 2 toxicity to humans
    very low oral toxicity
  86. group 2 symptoms
    • inhibits plant growth
    • chlorosis
    • terminal bud death
    • purple colouration
    • death is slow
  87. group 2 soil residual activity
    • adsorption in soil affects persistence of these products in soil
    • as soil pH decreases, herbicide adsorption increases as does persistence
  88. group 2 herbicide resistance
    • target site and metabolism based resistance
    • focused on Imidazolinone resistant crops
  89. group 4 herbicides
    auxinic herbicides
  90. group 4 kow and pka
    • pka bw 2 and 4
    • weak acids and water soluble
  91. group 4 uptake and translocation
    • systemic
    • rapid translocation
    • phloem translocation
  92. group 4 site of action
    • AUX/IAA repressor protein
    • when IAA is around T1R1 it can degrade the surpressor protein
    • acts like an uncontrollable auxinic hormone in broadleaf plants
  93. group 4 target species
    broadleaves mostly
  94. group 4 symptoms
    • twist and shout
    • eventually death
    • red discoloration
  95. group 4 soil residual activity
    • depends on rate of degradation by soil microbes
    • some long residual activity, some short
  96. group 4 herbicide resistance
    yes, but relatively low
  97. group 5,6,7 herbicides
    PS II inhibiting herbicides, light dependent reactions
  98. group 5,6,7 kow and pka
    most are water soluble, most are NOT weak acids
  99. group 5,6,7 uptake and translocation
    • good uptake from foliar application w application of surfactant
    • application to soil associated with translocation via xylem
  100. group 5,6,7 site of action
    affect plastoquinone binding and prevent electron movement
  101. group 5,6,7 where in plant
    thylakoid membrane
  102. group 5,6,7 metabolism
    • 1. conjugation with glutathione followed by movement to vacuole
    • 2. non-enzyme hydroxylation
    • 3. removal of side chains (P450 mediated)
  103. group 5,6,7 target species
    effective on broadleaves and grasses
  104. group 5,6,7 toxicity
    highly variable toxicity
  105. group 5,6,7 symptoms
    rapid activity, plant dies from radical formation and subsequent membrane damage
  106. group 5,6,7 soil residual activity
    • some problems since its water soluble
    • ex. atrazine has a half life of 146 days
  107. group 5,6,7 herbicide resistance
    yes, over 100 plants resistance since 1968, usually due to target site mutation
  108. group 10 herbicides
  109. group 10 kow and pka
    • kow: v water soluble
    • pka: 2, 2.9, 9.5
  110. group 10 site of action
    • glutamine synthase enzyme
    • blocking of enzyme leads to buildup of ammonia and glyoxylate
  111. group 10 where in plant
    chloroplast and cytoplasm
  112. group 10 metabolism
    • pat gene comes from a microbe, which inactivates ppt by acetylation
    • resistant plant have these 2 genes
  113. group 10 target species
    non-selective, effects everything
  114. group 10 toxicity
    low mammalian toxicity
  115. group 10 symptoms
    • chlorotic lesions at point of contact, spreads across leaf
    • rapid chlorosis
    • wilting and necrosis
  116. group 10 soil residual activity
    no significant soil residual
  117. group 10 resistance
    if they have the bar or pat gene they will be resistant?
  118. group 14 herbicides
    • peroxide bleaching herbicides
    • light dependent herbicide
  119. group 14 pka and kow
    • kow: intermediate
    • pka: no affective pka
  120. grup 14 uptake and translocation
    • uptake v rapid in most plants
    • foliar applied plants don't translocate
    • soil applied can translocate from roots to foliage
  121. group 14 site of action
    block PPO enzyme, stops heme and chlorophyll production
  122. group 14 where in plant
  123. group 14 metabolism
    • metabolism contributes to differential selectivity
    • metabolism must be fast to make life or death difference in plant
  124. group 14 toxicity
  125. group 14 symptoms
    • initial symptoms: water soaked spots, colour changes from green->yellow->brown black
    • after 24hrs: wilting, dessication, chlorosis
  126. group 14 soil residual activity
    binds strongly to soil colloids, low leaching probability
  127. group 27 herbicides
    popular one in AB: pyrasulfotole
  128. group 27 kow and pka
    • log kow: 0.276 at pH of 4
    • pKa: 4.2
  129. group 27 uptake and translocation
    • foliar uptake, weak acid herbicide with moderate solubility in water
    • translocated in xylem and phloem
    • pyrasulfotole translocated to plant's meristematic regions
  130. group 27 site of action
    inhibits enzyme HPPD
  131. group 27 where in plant
    meristematic regions
  132. group 27 target species
    broadleaf weeds in grasses
  133. group 27 symptoms
    foliar bleaching
  134. group 27 soil residual activity
    short residual period
  135. group 27 resistance
    • no??
    • but helps control group 2 resistant broadleaves
  136. group 27 herbicides mixed with???
    group 6 -> bromoxynil
Card Set
Pl Sc 352 Final
from midterm to final lectures