We observed a 50% reduction of O. crenata radicle when Ltryptophan
was applied at concentrations of 2.9 μg/mL. This is
in agreement with reported inhibition of root growth of
bindweed when applied at ≥2 μg/mL26 and of cockscomb,
cress, and lettuce at ≥28 μg/mL.3
We found that scopoletin inhibits O. crenata radicle growth
and causes a darkening of groups of radicle cells (data not
shown) potentially due to necrosis. This was observed at
concentrations ≥7 μg/mL, reaching a maximum of 50−60% of
the radicles at ≥13 μg/mL. Scopoletin causes the same
allelopathic effect, including the necrosis-like reaction of in vitro