Tolerant weeds paraquat

Faulkner, J.S. and B.M.R. Harvey. 1981. Paraquat tolerant Lolium perenne L. effects of paraquat on germinating seedlings. Weed Res. 21 29-36. 

In the concentrations used for aquatic weed control (diquat 1 ppm, paraquat 5 ppm) bipyridylium herbicides are not toxic to fish. The tolerance limit for the diquat cation is 6-12 ppm, for paraquat 125 pmm. The sensitivity of single fish species differs considerably. Owing to adsorption on mineral and organic colloids, rapid inactivation occurs in natural waters (Wurtz and Arlet, 1964 Howe and Wright,... 

Although paraquat is used as a broad spectrum total-kill herbicide, tolerance has been found in certain lines of Lol tvm perenne (41) and the weed Conyza (42) (Figure 11). In both instances, tolerant lines showed a lack of effect on carbon dioxide fixation, indicating reduced penetration of herbicide (42, 43) (Figure 12). Tolerant lines of Lotivm perenne were nevertheless shown to possess greater superoxide dismutase activity as well as greater catalase and peroxidase activities... 

Unlike tolerance of weeds to PSII herbicides, tolerance to paraquat or diquat is neither as widespread or as well understood. Furthermore, the level of tolerance is of a much lower level. ... 

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