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CRSS4340 Final Exam Questions And
Answers.
What are the 5 options for herbicides after foliar application? - Answers✔- Loss from leaf
surface
- Dry down of spray deposit
- Penetration of the cuticle
- Penetration and movement
- Penetration, mvmt, and translocations
What kind of plants have greater reception of herbicide? - Answers✔Plants with horizontal
leaves (90 degrees) have greater retention of droplets
How can we get greater reception of herbicide in plants that do not have ideal anatomy? -
Answers✔We can modify spray nozzles to improve coverage
What are some aspects of leaf anatomy to consider when applying herbicide? - Answers✔- shape
and area of leaves
- angle and orientation of leaves
- specialized features that may affect accumulation (EX: Whorls, rosettes)
What are some specialized structures of leaves that affect application? - Answers✔Trichomes or
leaf hairs: pattern and nature can affect the wettability of the leaf
Stomata and guard cells:
Define herbicide - Answers✔Chemicals used to manipulate or control undesirable vegetation;
any chemical agent that kills or greatly inhibits plant growth
What are the three types of herbicide selectivity? - Answers✔- Placement
- Herbicide Fate
1
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- Plant factors
Define placement selectivity in herbicide use - Answers✔Placing herbicides in a manner that
sensitive crop does not intercept; can be temporal or spatial
Define Temporal placement selectivity - Answers✔place herbicides in time so that crop plant is
unaffected - used in dormant and preplant
Define Spatial placement selectivity - Answers✔Place herbicide so that crop does not intercept -
used in post-directed
What are the options for the fate of the herbicide after application? - Answers✔- Can be washed
from plant surface and deposited onto the soil
- Can remain on plant surface, volatize, and photodegrade
- Penetrate and enter the plant - cmpds are then; conjugated into sugars and amino acids,
oxidized and reduced, reaches site of action
What are the three things that impact plant factors in herb selectivity - Answers✔- Plant age
(younger = more susceptible)
- Morphology (root depth, leaf properties)
- Biochemical differences (metabolic differences)
Define mechanism of action - Answers✔The way in which the herbicide kills the plant (EX:
Amino Acid synthesis inhibitor)
Define site of action - Answers✔Specific process in plants that a chemical disrupts (EX: EPSP
synthase inhibitor)
Define herbicide family - Answers✔Subcategory within each site of action
Define active ingredient - Answers✔Ingredient in an herbicide responsible for phototoxicity
Define "lock and key" model - Answers✔The idea that a substrate and enzyme fit together like a
lock and key; living systems recognize molecules by shape
Define Mode of Action - Answers✔Response of the plant to phytotoxic effects of an herbicide;
how the plant responds to the herbicide
Define mechanism of action - Answers✔Biochemical and biophysical responses of plant to the
herbicide; what process in inhibited leading to mode of action
MECHANISM OF ACTION --> MODE OF ACTION
2
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Define a primary mechanism of action - Answers✔Plant processes affected by lowest phytotoxic
dose of herbicide
Define a secondary mechanism of action - Answers✔Other plant processes affected by herbicide
Define contact herbicides - Answers✔Foliar applied herbicides that cause localized injury to
point of application - they are poorly or non-translocated
Define systemic herbicides - Answers✔Soil and foilar-applied herbs translocated from point of
entry site of phytotoxicity
Describe how a systemic herbicide works - Answers✔- Disrupts one or more normal plant
physiological or biochemical process
- Translocated from site of entry to site of phytotoxicity via apoplast or symplast
What is the biggest difference between contact and systemic herbicides? - Answers✔Contact act
locally for phytotoxicity, systemic are transported within the plant for phytotoxicity
*the seq of events occurring from the time of application until phytotoxicity is complicated -
many aspects are not well understood
Describe the movement in a plant of a symplastic herbicide - Answers✔- Travels through the
symplast (part of cell bound by a membrane) using plasmodesmatal connections between cells
- Moves in multiple directions
- More mobile in the phloem (food, carbs, etc)
- May be more effective in perennials bc it pulls herbicide into roots and sinks
Describe the movement in a plant of a apoplastic herbicide - Answers✔- Travels through the
apoplast (the cell wall region and intercellular spaces) and never crosses the membrane
- More mobile in the xylem
- Only moves in one direction - "up & out"
- Can be seen in the largest, bottom storage levels
Describe the movement of sugars through the phloem - Answers✔- Back and forth movement,
can move up and down
Describe WSSA 1 - Answers✔- Lipid Synthesis Inhibitor
- Inhibits prod on plant lipids in growing plants (selective grass control - no activity on broadleaf
species)
- Major crops: broadleaf, veggie crops, herb./woody ornamentals
3
CRSS4340 Final Exam Questions And
Answers.
What are the 5 options for herbicides after foliar application? - Answers✔- Loss from leaf
surface
- Dry down of spray deposit
- Penetration of the cuticle
- Penetration and movement
- Penetration, mvmt, and translocations
What kind of plants have greater reception of herbicide? - Answers✔Plants with horizontal
leaves (90 degrees) have greater retention of droplets
How can we get greater reception of herbicide in plants that do not have ideal anatomy? -
Answers✔We can modify spray nozzles to improve coverage
What are some aspects of leaf anatomy to consider when applying herbicide? - Answers✔- shape
and area of leaves
- angle and orientation of leaves
- specialized features that may affect accumulation (EX: Whorls, rosettes)
What are some specialized structures of leaves that affect application? - Answers✔Trichomes or
leaf hairs: pattern and nature can affect the wettability of the leaf
Stomata and guard cells:
Define herbicide - Answers✔Chemicals used to manipulate or control undesirable vegetation;
any chemical agent that kills or greatly inhibits plant growth
What are the three types of herbicide selectivity? - Answers✔- Placement
- Herbicide Fate
1
, ©FYNDLAY
- Plant factors
Define placement selectivity in herbicide use - Answers✔Placing herbicides in a manner that
sensitive crop does not intercept; can be temporal or spatial
Define Temporal placement selectivity - Answers✔place herbicides in time so that crop plant is
unaffected - used in dormant and preplant
Define Spatial placement selectivity - Answers✔Place herbicide so that crop does not intercept -
used in post-directed
What are the options for the fate of the herbicide after application? - Answers✔- Can be washed
from plant surface and deposited onto the soil
- Can remain on plant surface, volatize, and photodegrade
- Penetrate and enter the plant - cmpds are then; conjugated into sugars and amino acids,
oxidized and reduced, reaches site of action
What are the three things that impact plant factors in herb selectivity - Answers✔- Plant age
(younger = more susceptible)
- Morphology (root depth, leaf properties)
- Biochemical differences (metabolic differences)
Define mechanism of action - Answers✔The way in which the herbicide kills the plant (EX:
Amino Acid synthesis inhibitor)
Define site of action - Answers✔Specific process in plants that a chemical disrupts (EX: EPSP
synthase inhibitor)
Define herbicide family - Answers✔Subcategory within each site of action
Define active ingredient - Answers✔Ingredient in an herbicide responsible for phototoxicity
Define "lock and key" model - Answers✔The idea that a substrate and enzyme fit together like a
lock and key; living systems recognize molecules by shape
Define Mode of Action - Answers✔Response of the plant to phytotoxic effects of an herbicide;
how the plant responds to the herbicide
Define mechanism of action - Answers✔Biochemical and biophysical responses of plant to the
herbicide; what process in inhibited leading to mode of action
MECHANISM OF ACTION --> MODE OF ACTION
2
, ©FYNDLAY
Define a primary mechanism of action - Answers✔Plant processes affected by lowest phytotoxic
dose of herbicide
Define a secondary mechanism of action - Answers✔Other plant processes affected by herbicide
Define contact herbicides - Answers✔Foliar applied herbicides that cause localized injury to
point of application - they are poorly or non-translocated
Define systemic herbicides - Answers✔Soil and foilar-applied herbs translocated from point of
entry site of phytotoxicity
Describe how a systemic herbicide works - Answers✔- Disrupts one or more normal plant
physiological or biochemical process
- Translocated from site of entry to site of phytotoxicity via apoplast or symplast
What is the biggest difference between contact and systemic herbicides? - Answers✔Contact act
locally for phytotoxicity, systemic are transported within the plant for phytotoxicity
*the seq of events occurring from the time of application until phytotoxicity is complicated -
many aspects are not well understood
Describe the movement in a plant of a symplastic herbicide - Answers✔- Travels through the
symplast (part of cell bound by a membrane) using plasmodesmatal connections between cells
- Moves in multiple directions
- More mobile in the phloem (food, carbs, etc)
- May be more effective in perennials bc it pulls herbicide into roots and sinks
Describe the movement in a plant of a apoplastic herbicide - Answers✔- Travels through the
apoplast (the cell wall region and intercellular spaces) and never crosses the membrane
- More mobile in the xylem
- Only moves in one direction - "up & out"
- Can be seen in the largest, bottom storage levels
Describe the movement of sugars through the phloem - Answers✔- Back and forth movement,
can move up and down
Describe WSSA 1 - Answers✔- Lipid Synthesis Inhibitor
- Inhibits prod on plant lipids in growing plants (selective grass control - no activity on broadleaf
species)
- Major crops: broadleaf, veggie crops, herb./woody ornamentals
3
