Chironex

James, as you mentioned, it is the two in combination creating a synergy that trigger ethylene production and the inhibition of abscisic acid (ABA). Each of these plays a role in releasing dormancy.
Cytokinens and ethrel stimulate ethylene production in seeds. Further, the synergistic effects of ethrel and kinetin in stimulating polyribosome formation.
Significant variables are temperature, (at 35 C germination is completely inhibited) 25C is ideal; and Light (ethrel is promoted by kinetin in releasing seeds from photodormancy in light, or GA3 induced dark germination). Kinetin is capable of overcoming the inhibition of germination by high temperature, as is ethrel to a lesser extent, but the two combined have been shown to increase both the rate and percentage of germination.
Both kinetin and ethrel appear to be related to the expansion of cotyledons. They work together to assist in ATP synthesis during dormancy release in some seeds.
I should also include that these experiments were initially conducted on lettuce and Xanthium seeds. The trials I will be conducting may be the first efforts on Musa and Ensete seeds. Hopefully similar results will be realized.

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Scot