regression lines showed that the essential oil of crabgrass
inhibited the shoot biomass allocation more prominently
than did that of wild oat (Fig. 2).
When wheat was exposed to the essential oils of wild
oat and crabgrass, the production of the allelochemical,
DIMBOA, was altered (Fig. 3). Both weeds’ essential oil
led to a great increase in the DIMBOA concentration in
the wheat seedlings in a time-dependent manner. The
largest increase was observed at the early incubation time
and then it declined. The DIMBOA concentration of
wheat that was exposed to the essential oils reached a
maximum of 0.49 mg g-1 (crabgrass) and 0.48 mg g-1
(wild oat) after 2 h of incubation. In addition, the wild
oat essential oil led to a greater DIMBOA concentration
than did the crabgrass essential oil after 2 h of incubation
(Fig. 3).