Interaction of gibberellins and fusicoccin in growth retardant- and far red light-inhibited germination of lettuce seeds

Germination of lettuce seeds cv. May Queen iscompletely prevented either with 10 µM tetcyclacisor with continuous FR illumination. GA₃ and the N-substituted phtalimide, AC 94,377, werepartially effective in overcoming tetcyclacis-inducedinhibition but ineffective on photoinhibited seeds. FCcompletely reversed tetcyclacis inhibition and inducedca. 60% germination in continuous FR light. Aninteraction between FC and GA₃ (as well asbetween FC and AC 94,377) was evident in stimulationof germination under both inhibitory conditions.Interaction was calculated as a ratio of thepercentage of seeds germinated under the simultaneousaction of stimulators compared to their additiveeffect. This was 2.54 for tetcyclacis- and 2.95 forphotoinhibited seeds. It is concluded that thistype of interaction is promotive synergism. Themagnitude of the interaction was highest if theapplication of FC was delayed after GA₃application, and the optimal time lag was 6 h fortetcyclacis-inhibited, or 24 h for photoinhibited seeds.