Characteristics of herbicidal injury by diphenyl ether herbicides oxyfluorfen and bifenox in Lemna pausicostata Hegelm.

Abstract

The herbicidal mode of action of diphenyl ethers oxyfluorfen (2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene) and bifenox (methyl-5-(2, 4-dichlorophenoxy)-2-nitrobenzoate) in Lemna pausicostata HEGELM. was investigated by monitoring an electrolyte leakage and a lipid peroxide decomposition product. Among the diphenyl ethers tested, these two herbicides caused intensive leakage in the plant after a lag period of 4-hr. Thiobarbituric acid-reacting material, product of lipid peroxide decomposition, content in a bathing solution was also increased. Light and oxygen were required for their action and by decreasing the light quantity, the effect of oxyfluorfen was delayed. Exogenously applied antioxidant α-tocopherol, and the scavengers of active oxygen species D-mannitol and hydroquinone partially protected from herbicidal injury. Protection was also partially afforded from phytotoxicity by the photosynthetic electron transport inhibitor, diuron. Although the mechanism of involvement of photosynthesis in the action is still unclear, active oxygen species were suggested to be involved in the initiation of lipid peroxidation.