Volatile methyl ketone seed-germination inhibitors fromAmaranthus palmeri S. Wats. Residues.

The effects of nine methyl ketones previously identified in the mixture of volatiles released byAmaranthus palmeri (AMAPA) residues upon onion, carrot, AMAPA, and tomato seed germination were determined. Three-day exposures to these volatiles significantly inhibited germination of all assay seeds, and the degree of inhibition was dependent upon seed species, exposure time, and concentration. Based on the degree of inhibition observed in both time- and concentration-dependent assays, the following activity series was obtained: 2-octanone, 2-nonanone > 2-undecanone > 2-heptanone > 2-hexanone, 3-methyl-2-butanone, 2-pentanone, 3-hydroxy-2-butanone > 2-butanone. The activities of these compounds appear to be additive and dependent on relative volatility and hydrophilicity.