Influence on Herbicide Uptake and Translocation

It is usually part of the investigations on the mechanism(s) of safener action to look for possible safener interactions with the herbicide partner at the process of herbicide uptake into the crop. Looking through the relevant literature gives a complex picture. This can also be seen in a review of Davies and Caseley [2], who present an exhaustive compilation of safener effects on herbicide uptake for relevant herbicide/safener combinations developed up to that time. Only in 20% of the cases was the uptake of the herbicide reduced in combination with the 

This observation, but also contradictory results of other studies, which showed either no effect or a stimulatory effect of N A on herbicide uptake, made it questionable that an interference with herbicide uptake plays a significant role for the mechanism of action of this safener [30, 31). It should be added that contradictory results (inhibition, stimulation or no effect on herbicide uptake) can also be found in the literature for other herbicide/safener combinations. 

Uptake studies were also carried out with the recently developed combinations of the safener mefenpyr-diethyl with the sulfonylurea herbicides mesosulfuron-methyl and iodosulfuron-methyl-sodium, which are used for selective postemergence weed control in wheat crop. In both combinations the safener had no influence on herbicide uptake [29]. 

In summary, it can be said that from present experience only in a few cases was herbicide uptake by the crop reduced in combination with a safener, and even then doubts remained as to whether the reduction of herbicide uptake was the mechanism of safener action. It is, therefore, concluded that interference with herbicide uptake by the crop has no importance as a mechanism of safener action, though it cannot be excluded that there may be cases where it plays an auxiliary role. 

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