Interaction of gibberellic acid and fusicoccin in abscisic acid-inhibited and thermo-inhibited germination of lettuce seeds

Abstract

Abstract - Germination of May Queen lettuce (Lactuca saliva L.) seeds is completely prevented either by 10-4 M abscisic acid (ABA) or at 31.5 °C. Gibberellic acid (GA3) and N-substituted phthalimide, AC 94,377, are almost ineffective in overcoming ABA-induced inhibition and thermo-inhibition, but fusicoccin (FC) completely reverts both tpes of inhibition. An interaction between FC and GA3 (as well as between FC and AC 94,377) is evident in stimulation of germination under both inhibitory conditions. The extent of interaction, calculated as a ratio of percent of seeds germinated under simultaneous action of stimulators and the sum of their separate effects is 2.25 for ABA­and 1.61 for thermo-inhibited seeds. The obtained data point to the promotive synergism as the type of interaction. The highest interaction occurs if the application of FC is delayed after GA3 application, the optimal time lag being 36 h for ADA-inhibited, or 24 h for thermo-inhibited seeds, respectively.