A new benzoxazolinone, 5-chloro-6-methoxy-2-benzoxazolinone (Cl-MBOA) caused growth inhibition of roots and shoots of oat (Avena sativa), timothy (Phleum pratense), crabgrass (Digitaria sanguinalis), ryegrass (Lolium multiflorum), cockscomb (Amaranthus caudatus), cress (Lepidium sativum) and lettuce (Lactuca sativa); increasing the dose of Cl-MBOA increased inhibition. The concentrations for 40% inhibition of root growth were 0.12, 0.14, 0.17, 0.19, 0.46, 0.57 and 0.76 mM for timothy, crabgrass, ryegrass, oat, cockscomb, cress and lettuce, respectively, and the concentrations for 40% inhibition of shoot growth were 0.25, 0.28, 0.36, 0.40, 7.9, 12.5 and 19.6 mM for timothy, crabgrass, ryegrass, cockscomb, cress and lettuce, respectively. The contents of Cl-MBOA in shoots and roots of 14-day-old maize (Zea mays) seedlings were 37.5 and 8.7 μg g-1 fr. wt. The presence of this compound in maize seedlings, coupled with its effect on growth, suggest that it may play an important role in maize allelopathy.
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