potential to inhibit electron transfer between Q A and Q B
at the reducing site of photosystem II (Czarnota et al.,
2001). When applied at a rate of 0.6kg ai/ha, sorgoleone
significantly inhibited growth of several broadleaf and
grass species (Table 2). The most affected weeds (>80%
inhibition) were black nightshade, redroot pigweed and
Ambrosia artemisiifolia L. (common ragweed). Com-
paratively, lesser affected (>40% inhibition) weeds were
Cassia obtusifolia L. (sicklepod), large crabgrass and
Abutilon theophrasti Medik. (velvetleaf). Sorgoleone was
applied to 14-day-old seedlings and data were collected
10 days after treatment. Although, sorgoleone is more
active in vitro in inhibiting PS II when compared to
atrazine, it is considered a weak herbicide due to its
physicochemical properties and short environmental
half-life