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16 Cards in this Set

  • Front
  • Back
What is the mechanism of action of imidazolinones?
Bind to enzyme ALS/AHAS inhibiting the synthesis of the AA valine, leucine and isoleucine causing decreased protein synthesis and cessation of plant growth
What are the symptoms of Imis?
susceptible weeds are severely stunted with shortened internodes; foliage of grass weeds may turn red to purplish in color
What is the mobility of Imis?
phloem mobile; rapidly absorbed by the foliage and roots, translocated to meristematic regions
What are the 2 mechanisms of ALS resistance?
1) enzyme mutation - less specific, possibility of cross resistance with sulfonylureas or urea
2) metabolism - more specific to an active ingredient by CP450 or multifunction oxidases (MFOs)
How can in furrow insecticides (organophosphates) distort corn when sprayed with an ALS compound like Imis and what is the effect on IR and IT corn?
Organophosphates reduce MFO activity in plants preventing metabolism
- IR corn unaffected b/c enzyme changed in process and cross resistantance to SUs
- IT corn was affected b/c 1 resistant gene isn't enough
What is the soil behavior of when Imis are applied?
- weakly bound at pH's above 6.5
- at low pH's, herbicides will be bound
- persistant in soil
- react with Al and Fe
Is there more activity with the Imis with fast growth or slow growth of the weeds?
fast growth
What herbicides inhibit the enzyme ALS?
Sulfonylanilides or Sulfonamides
What Glufosinate PRE, PPI or POST and is it selective or non-selective?
POST, non-selective
How can you tell if your corn is Bt corn?
Bt corn is glufosinate-resistant so if you spray it with glufosinate and it doesn't die then it is Bt corn
What is the mechanism of glufosinate?
inhibits the activity of glutamine synthetase in the plastid and cytosol - responsible for the conversion of ammonia into amino acids; causes a build up of toxic levels of ammonia, leading to cellular disruption and tissue death
What is the tolerance of unaffected plants to glufosinate?
enhanced metabolism by insertion of bar gene from Streptomyces hygroscopicus
What is the mode/mechanism of action of glyphosate?
- absorbed by leaf and green tissue (POST), undergoes extensive translocation in photosynthate stream to regions of action growth
- highly stable within plant
- weak acid
- inhibits amino acid and protein synthesis, specifically EPSP synthase
- symptoms include lemon yellowing, wiliting and necrosis of young foliage
Why does glyphosate have no soil activity?
because of phosphorus group
What amino acids, etc does glyphosate block?
- Tyr, Phe, Trp
- auxins
- phytoalexins
- pentose phosphate shunt
How are resistant or "Roundup Ready" crops tolerant to glyphosate?
insertion of 'wild type' enzyme- CP4 gene
- this gene codes for the altered EPSP synthase (Gly -> Ala) and expressed at high levels to make multiple copies of less sensitive enzyme
- when glyphosate is applied, the native enzyme is inhibited by the CP4 allows the production of the necessary amino acids