Target sites paraquat

The other major class of herbicides involved with photosynthesis are compounds that act as divertors of electron flow at photosystem I (PSI). After the initial discovery of diquat and paraquat in the late 1950s, other related compounds have had limited use. One of these, morfamquat, has now been withdrawn. Thirty years later, there are no new chemicals or herbicide families to rival paraquat and diquat at this particular target site. We have, however, an increased understanding of the nature of the damaging radical species that are generated as a result of the action of these compounds. With these herbicides, as also with the electron transport inhibitors, toxic oxygen species have a major role. 

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