Comparisons of Dihydroxybenzenes and Paraquat

Although similar in mode of action, 1,2-dihydroxybenzene (catechol) and 1,1′-dimethyl-4,4′bipyridinium ion (paraquat) at different levels were required to kill plants. Both chemicals were fast-acting, they both required light to be active, and herbicides that inhibit photosynthesis protected the plants temporarily against the action of both compounds. Paraquat and catechol had additive effects on black nightshade (Solanum nigrum L.) but not on redroot pigweed (Amaranthus retroflexus L.). Catechol protected redroot pigweed against the action of paraquat.