Cuminaldehyde, the major component of cumin seed oil, inhibits seed germination at high doses, but shows normal root hair elongation on normal length roots at low doses. Cuminaldehyde is not likely the allelochemical in cumin seeds. Cuminyl alcohol, the second-most abundant component of cumin seed oil, inhibits lettuce germination at high doses, and inhibits root hair elongation on normal length roots at low doses. Cuminyl alcohol is the most-likely allelochemical in cumin seeds. The effects of various Apiaceae and their essential oil components.
Lower case means mild, proportional.
All Apiaceae seeds examined inhibit seed germination of lettuce at high densities. At lower seed densities, fennel and cumin seeds inhibit root and root hair elongation respectively. Fenchone inhibits root elongation in lettuce at low doses when germination is high with normal root hair elongation. Fenchone is the likely allelochemical in fennel seed. Cuminyl alcohol inhibits root hair elongation in lettuce at low doses when germination is high with normal root elongation.