Inhibition and promotion of germination by several sesquiterpenes.

The sesquiterpene lactones, burrodin, confertiflorin. desacetyl-confertiflorin, dihydroparthenolide, parthenin, and 7α-hydroxy-3-desoxyzaluzanin C, and the sesquiterpene ester guayulin A were assayed at concentrations of 1, 10, and 100 μM for effects on seed germination of 16 dicot and nine monocot species. Six of the dicot and two of the monocot species were affected by one or more of these compounds. Germination was both inhibited and promoted, depending on the compound and the specific species or cultivars, at concentrations as low as 1 μM. For example, guayulin A, which promoted the germination of lettuce at all concentrations tested, inhibited the germination of tomato. Confertiflorin stimulated germination of the lettuce cultivar Grand Rapids at 1 μM, but inhibited germination of a light-sensitive cultivar at all concentrations tested.