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Paraquat resistance in conyza.
E P Fuerst1, H Y Nakatani, A D Dodge
1MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824.
Plant Physiology
|April 1, 1985
Summary
Egyptian Conyza bonariensis resistant to paraquat herbicide shows no difference in uptake or photosystem I activity. Resistance is linked to herbicide exclusion from chloroplasts, likely via sequestration.
Area of Science:
- Agricultural Science
- Plant Biology
- Biochemistry
Background:
- Paraquat (1,1'-dimethyl-4,4'-bipyridinium ion) is a widely used herbicide.
- Herbicide resistance in weeds is a significant agricultural challenge.
- A biotype of Conyza bonariensis from Egypt exhibits resistance to paraquat.
Purpose of the Study:
- To investigate the mechanism of paraquat resistance in an Egyptian biotype of Conyza bonariensis.
- To determine if resistance is due to differential uptake, altered photosystem I activity, or other factors.
Main Methods:
- Radiolabeled [(14)C]paraquat uptake and movement studies.
- In vitro photosystem I partial reaction assays with paraquat and related compounds.
- In vivo chlorophyll fluorescence measurements.
- Analysis of paraquat binding to isolated cell walls.
Main Results:
- Paraquat uptake was greater in the resistant biotype, ruling out reduced uptake as the resistance mechanism.
- Photosystem I activity was not altered in the resistant biotype, excluding changes at the electron acceptor level.
- Paraquat did not quench chlorophyll fluorescence in the resistant biotype, indicating exclusion from chloroplasts.
- Movement of paraquat was restricted in excised leaves of the resistant biotype.
Conclusions:
- Paraquat resistance in this Conyza bonariensis biotype is not due to reduced uptake or altered photosystem I.
- The primary mechanism appears to be the exclusion of paraquat from chloroplasts via a rapid sequestration process.
- Further research is needed to identify the precise site and mechanism of paraquat sequestration.
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