Effect of Low Temperatures and Different Growth Regulators on Seed Germination in Cyclopia spp

The synthesis and action of ethylene are absolute requirements for seed germination in Cyclopia intermedia (resprouter) and C. subternata (seeder). Stratification at 2 °C in the dark resulted in the breaking of dormancy in the resprouter and the stimulation of the initial rate of germination in the seeder. The dormancy-breaking effect of low temperatures could be substituted for by treatment with ethylene, GA₃ or BA. However, in the seeder, only ethylene could mimic the effect of stratification on the rate of seed germination. Inhibition of ethylene action by NBD inhibited the dormancy-breaking effect of stratification, ethylene, GA₃ and BA in the resprouter and suppressed germination in the seeder to the levels of the resprouter. Stratification or treatment with GA₃ and BA resulted in the suppression of ethylene production due to the suppression of the conversion of ACC to ethylene. The results of this study indicate that the effects of stratification, GA₃ and BA on dormancy-breaking and germination could be ascribed to the effects of these treatments on the ability of the seeds to react to ethylene.