Lecture 17 - Group 22 and 27 Flashcards
group 22 mode of action
inhibitors of photosystem 1
t/f: group 22 is a selective, contact herbicide
f, it is a non selective, contact herbicide
what group is diquat and paraquat in
22
how does the group 22 mode of action work
diverts electrons from PS1 and causes production of toxic O2 radicals. Produces leakage of cell contents and rapid desiccation
symptoms of group 22
- rapid contact bleaching or chlorosis
- accelerated senescence
- localized burnoff
basis of selectivity of group 22
non
peculiarities of group 22
- more active on young, rapidly growing weeds
- quickest action in bright sun but best results on cloudy days
- increase pod shattering when used as desiccant
- use non-ionic surfactant
- corrosive
- weed resistance
group 27 mode of action
HPPD (4-hydroxyphenylpyruvate dioxygenase) inhibitors
t/f: group 27 is a systematic, selective herbicide
t
what is group 27 applied on
annual grasses and broadleaves at pre and post-emergence
group 27 herbicide families
- triketones
- isoxazoles
- benzoyl pyrazoles
how does group 27 mode of action work
inhibits HPPD which is the key enzyme in plastoquinone biosynthesis (important transporter of electrons between PS1 and 2) and restricts plants ability to generate energy. also loss of chlorophyll and vit E production
symptoms of group 27
- bleaching
- new shoot tips and leaves bleached, white, or tinged pink or purple
group 27 basis of selectivty
- rapid metabolism to inactive compounds
- lower sensitivity of 4-HPPD target enzyme
group 27 peculiarities
- rapidly taken up by roots and shoots
- systemically translocated
- herbicide resistant weeds
- HPPD resistant crops
