Promotion by gibberellin of lettuce seed germiation as a function of presoaking period

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Abstract
Germination of lettuce seeds (Lactuca sativa L. cv. Grand Rapids) was examined in the presence of various doses (10−5.0–10−3.0 M) of gibberellic acid applied at various times (hour 0–8) of soaking. Germination promotion by gibberellic acid was greater as the dose of gibberellic acid was increased and attenuated with the length of the presoaking period. As an exception, ca. 95% germination was always evoked by the largest dose (10−3 M) of gibberellic acid given at any time of soaking. The dose-response curve obtained for each presoaking period had a distinct sigmoidal profile. Synergistic and photoreversible promotion by red light of the gibberellin-induced germination was also investigated. Far-red light pulse given 6 hr after the red pulse was still effective in removing the red light action. Application of enzyme kinetics to the gibberellin action and also to the synergism between gibberellin and red light was suggested.