Role of Ethylene and Short-Chain Saturated Fatty Acids in the Smoke-Stimulated Germination of Cyclopia Seed

The seeds of both Cyclopia intermedia and Cyclopia subternata exhibited a seed coat imposed dormancy. However, seeds of the former species also exhibited an embryo dormancy which could be broken by exposure to smoke or ethylene. This stimulating effect of smoke and ethylene was inhibited by exposure to NBD, indicating that ethylene in the smoke was responsible for the stimulation of germination. The involvement of ethylene in germination in both species was clearly demonstrated by the inhibition of germination after treatment with AOA. Differences in germination between the two species can not be ascribed to differences in ethylene production. Seeds of C. subternata, however, showed a much higher capacity to bind ethylene than seeds of C. intermedia. Pulse treatments with octanoic acid or smoke-saturated water stimulated germination in C. intermedia due to an increase in ethylene sensitivity, while longer treatments inhibited germination in both species. It appears that octanoic acid present in smokesaturated water was responsible for the reaction of the seeds to the water.