The involvement of ethylene in determining seed vigor and the time required for the completion of germination

Differences in seed vigor influenced the ability of sweet corn and tomato seeds to produce ethylene during imbibition. High vigor seeds evolved a larger amounts of ethylene than low vigor seeds when exogenous 1-aminocyclopropane-1-carboxylic acid (ACC) was applied. ACC content remained higher in aged sweet corn and tomato seeds. Northern blot analyses of total RNA of sweet corn and tomato with a tomato ACC-oxidase antisense RNA probe detected a transcript 48 hours after imbibition in high vigor seeds on 5 mM ACC for sweet corn or water and 5 mM ACC for tomato. The ability to produce ethylene from seeds imbibed on ACC would be a biochemical marker positively correlated with seed vigor.; Exogenous application of ACC or ethylene reduced the time to complete germination in tomato, sweet corn, and Arabidopsis seeds. However, exogenous application of ethylene to tomato and sweet corn seed during imbibition caused either a decrease or an increase in the time required for radicle protrusion, depending on when seeds were first exposed to ethylene. Exogenously applied ACC could not replace gibberellic acid (GA) for the completion of germination in gib-1 tomato (GA deficient mutant). In addition, no interaction between GA and ACC was found. Exogenous ACC applied to high vigor sitw tomato (abscisic acid insensitive mutant) seeds showed no differences in time required for radicle protrusion. In contrast, low vigor sitw tomato seeds treated with ACC showed increased germination speed. In contrast, aba2 Arabidopsis , (ABA insensitive mutant) seeds treated with different concentrations of ACC had a reduction in time required for 25 and 50 percent germination.; Nr ethylene-insensitive, gain-of-function (GOF) tomato mutant seeds complete germination faster than wild type seeds. Both wild type and Nr seeds treated with ethylene action inhibitors (NBD and STS) required more time to initiate radicle emergence than non-treated seeds. In Arabidopsis, evidence was more compelling for ethylene's involvement in determining length of the lag phase of germination. Single GOF and loss-of-function (LOF) mutations in ETR1 generally resulted in slower germination. In addition, one of the double LOF mutants (etr1–6/etr2–3) had faster germination than wild type seeds.