Influence of Norflurazon on the Activation of Substituted Diphenylether Herbicides by Light

Oxyfluorfen [2 - chloro -1 - (3 - ethoxy - 4 - nitrophenoxy) -4 - (trifluoromethyl)benzene] and RH-8817 {ethyl 5 - [2-chloro - 4 -{trifluoromethyl) phenoxy] - 2 - nitrobenzoate} require light for activation. Removal of carotenoids by treating corn (Zea maysL.) seedlings with norflurazon [4 - chloro - 5 - (methylamino) - 2 - (α, α, α - trifluoro -m- tolyl) - 3 (2H) - pyridazinone] rendered them partially tolerant of oxyfluorfen and RH-8817 even when grown in the light. The activation of substituted diphenylether herbicides may occur as a result of the absorption of light energy by carotenoids.