CRSS4340 Final Exam With
Complete Solution
What are the 5 options for herbicides after foliar application? - ANSWER -
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? - ANSWER 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? - ANSWER We can modify spray nozzles to improve coverage
What are some aspects of leaf anatomy to consider when applying herbicide?
- ANSWER - 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? -
ANSWER Trichomes or leaf hairs: pattern and nature can affect the
wettability of the leaf
Stomata and guard cells:
,Define herbicide - ANSWER 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? - ANSWER - Placement
- Herbicide Fate
- Plant factors
Define placement selectivity in herbicide use - ANSWER Placing herbicides in
a manner that sensitive crop does not intercept; can be temporal or spatial
Define Temporal placement selectivity - ANSWER place herbicides in time so
that crop plant is unaffected - used in dormant and preplant
Define Spatial placement selectivity - ANSWER Place herbicide so that crop
does not intercept - used in post-directed
What are the options for the fate of the herbicide after application? -
ANSWER - 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 -
ANSWER - Plant age (younger = more susceptible)
- Morphology (root depth, leaf properties)
- Biochemical differences (metabolic differences)
Define mechanism of action - ANSWER The way in which the herbicide kills
,the plant (EX: Amino Acid synthesis inhibitor)
Define site of action - ANSWER Specific process in plants that a chemical
disrupts (EX: EPSP synthase inhibitor)
Define herbicide family - ANSWER Subcategory within each site of action
Define active ingredient - ANSWER Ingredient in an herbicide responsible for
phototoxicity
Define "lock and key" model - ANSWER The idea that a substrate and enzyme
fit together like a lock and key; living systems recognize molecules by shape
Define Mode of Action - ANSWER Response of the plant to phytotoxic effects
of an herbicide; how the plant responds to the herbicide
Define mechanism of action - ANSWER Biochemical and biophysical
responses of plant to the herbicide; what process in inhibited leading to
mode of action
MECHANISM OF ACTION --> MODE OF ACTION
Define a primary mechanism of action - ANSWER Plant processes affected by
lowest phytotoxic dose of herbicide
Define a secondary mechanism of action - ANSWER Other plant processes
affected by herbicide
Define contact herbicides - ANSWER Foliar applied herbicides that cause
localized injury to point of application - they are poorly or non-translocated
Define systemic herbicides - ANSWER Soil and foilar-applied herbs
translocated from point of entry site of phytotoxicity
Describe how a systemic herbicide works - ANSWER - 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? -
ANSWER 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 - ANSWER -
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 - ANSWER -
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 - ANSWER - Back and
forth movement, can move up and down
Complete Solution
What are the 5 options for herbicides after foliar application? - ANSWER -
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? - ANSWER 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? - ANSWER We can modify spray nozzles to improve coverage
What are some aspects of leaf anatomy to consider when applying herbicide?
- ANSWER - 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? -
ANSWER Trichomes or leaf hairs: pattern and nature can affect the
wettability of the leaf
Stomata and guard cells:
,Define herbicide - ANSWER 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? - ANSWER - Placement
- Herbicide Fate
- Plant factors
Define placement selectivity in herbicide use - ANSWER Placing herbicides in
a manner that sensitive crop does not intercept; can be temporal or spatial
Define Temporal placement selectivity - ANSWER place herbicides in time so
that crop plant is unaffected - used in dormant and preplant
Define Spatial placement selectivity - ANSWER Place herbicide so that crop
does not intercept - used in post-directed
What are the options for the fate of the herbicide after application? -
ANSWER - 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 -
ANSWER - Plant age (younger = more susceptible)
- Morphology (root depth, leaf properties)
- Biochemical differences (metabolic differences)
Define mechanism of action - ANSWER The way in which the herbicide kills
,the plant (EX: Amino Acid synthesis inhibitor)
Define site of action - ANSWER Specific process in plants that a chemical
disrupts (EX: EPSP synthase inhibitor)
Define herbicide family - ANSWER Subcategory within each site of action
Define active ingredient - ANSWER Ingredient in an herbicide responsible for
phototoxicity
Define "lock and key" model - ANSWER The idea that a substrate and enzyme
fit together like a lock and key; living systems recognize molecules by shape
Define Mode of Action - ANSWER Response of the plant to phytotoxic effects
of an herbicide; how the plant responds to the herbicide
Define mechanism of action - ANSWER Biochemical and biophysical
responses of plant to the herbicide; what process in inhibited leading to
mode of action
MECHANISM OF ACTION --> MODE OF ACTION
Define a primary mechanism of action - ANSWER Plant processes affected by
lowest phytotoxic dose of herbicide
Define a secondary mechanism of action - ANSWER Other plant processes
affected by herbicide
Define contact herbicides - ANSWER Foliar applied herbicides that cause
localized injury to point of application - they are poorly or non-translocated
Define systemic herbicides - ANSWER Soil and foilar-applied herbs
translocated from point of entry site of phytotoxicity
Describe how a systemic herbicide works - ANSWER - 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? -
ANSWER 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 - ANSWER -
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 - ANSWER -
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 - ANSWER - Back and
forth movement, can move up and down
