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

Abstract

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.