Lecture 12 Flashcards
herbicide uptake and translocation
1
Q
How do herbicides work?
A
- Penetrate the way leaf or root hair
- move through the watery space around the cell
- enter the cell by passing through an oily membrane
- reach the target site
- inhibit the target
2
Q
uptake and translocation affected by:
A
-The physiochemical properties of the herbicide
- Weed biology
-Environmental factors prior to and following application
3
Q
foliar uptake applied to:
A
applied to shoots
4
Q
barriers to herbicide penetration
A
1) surface roughness of leaves
2) epicuticular waxes - cuticle
3) cell wall
4) cell membrane
5
Q
epicuticular waxes / cuticle - barrier
A
- waxy
- hydrophobic
- more permeable to lipid soluble compounds (adjuvants)
- herbicide moves by diffusion
6
Q
cell wall - barrier
A
- hydrophilic cellulose strands
- little resistance
- moves through diffusion by concentration gradient
7
Q
lipophobic compounds through cell wall
A
- diffuse slowly through cuticle
- diffuse more rapidly through cell wall
8
Q
hydrophobic compounds through cell wall
A
- diffuse quickly through cuticle
- may be trapped there because of very slow diffusion through cell wall
9
Q
Cell membrane - barrier
A
- semi permeable
- most herbicides require active transport (not diffusion)
10
Q
root uptake:
A
- soil applied herbicides move into plant through roots or stem of emerging seedling
- enter roots by mass flow with water
11
Q
casparian strip - barrier
A
-lignified waxy layer in endodermis layer
12
Q
A
13
Q
Ambimobile
A
Move in either phloem or xylem
ex. glyphosate
14
Q
immobile
A
often lipophilic and unable to be translocated
ex. contact herbicides
diquat
15
Q
factors affecting uptake and translocation:
A
- Soil pH can affect root uptake (affects water solubility)
- environmental conditions affect foliar absorption
(adequate moisture/temp optimizes plant growth) - leaf orientation
