The mechanisms of selective herbicidal action of
sethoxydim were investigated by using cultured root tips of corn (Zea mays L. cv Goldencrossbantam) and pea (Pisum sativum L. cv Alaska). Meristematic cells in the cultured roots were arrested in G(1) and G(2) of the cell division cycle by
sucrose starvation and resumed growth and cell division (proliferation) when
sucrose was provided. Corn root growth after
sucrose addition was inhibited by
sethoxydim at concentrations of 0.01 micromolar and greater when roots were treated in the presence of
sucrose but was not inhibited
at 10 micromolar
sethoxydim when they were treated during
sucrose starvation. Greater absorption of [(14)C]
sethoxydim into the meristematic region of corn roots was observed when cells were in proliferative condition but not when they were arrested by
sucrose starvation, whereas no greater absorption of the
herbicide into pea meristems was observed in either growth condition. In the cell cycle study, greater absorption of [(14)C]
sethoxydim into the corn root meristem was observed at a certain limited time before S (
DNA synthesis) stage. The physiological effects and the greater absorption of
sethoxydim clearly depended on cell cycle progression of corn root meristem, whereas
fatty acid synthesis, as well as its inhibition by
sethoxydim, was not associated with either cell cycle progression or greater absorption of the
herbicide.