Title: Weed Biology and Herbicides
1Weed Biology and Herbicides
- Weeds
- Reasons for success
- Problems for agriculture
- Herbicides
- Demand
- R D Costs
- Modes of Action
2What are pests?
Major weed plant families
grass
potato
morning glory
spurge
bean
3Reasons for success
- High reproductive rates
- Seed reservoirs
Vs. crop
43. Mimicry in hand weeded rice fields
Barnyardgrass
Rice
5Seed Mimicry mechanical harvesters
Lentil mimic
Normal vetch
Lentil
64. C4 Photosynthesis
C3 costs 18 ATP, but CO2 lost at high temps C4
costs 30 ATP, but CO2 loss at minimized in
bundle sheath cells
C4 Photo-synthetic Advantage
Light
Temperature
78/10 Worst weeds use C4 photosynthesis
8Problems for agriculture
1. Yield Losses
92. Difficult crop handling
3. Decreased crop quality
4. Reservoirs of pests pathogens Or
5. Hybridization
Sorghum bicolor x Sorghum halpense good bad
Aggressive perennial Few seeds Fast vegetative
growth
Horizontal gene transfer ??