Dormancy Resulting from Gamma-irradiation of Lettuce Seed

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Abstract
Lettuce seeds given 300–1000 kr of gamma-rays show inhibition of germination when subsequently put into water. That this failure to germinate was caused by seed dormancy was suggested by the fact that such irradiated seeds did germinate if treated with any of the following germination-stimulating agents: gibberellic acid, kinetin, thiourea, pricking, or light. Germination was accompanied by cellular expansions and cell divisions, irrespective of radiation and chemical treatments. The first four agents mentioned were fully effective under conditions where continuous white light was not. The chemical treatments, which reversed the gamma-radiation effects on germination, gave no reversal of any of the following gamma-radiation effects: inhibition of respiratory rates, production of chromosomal aberrations, and reduction in seedling height. Consequently, the chemical treatments that enabled gamma-irradiated seeds to germinate had radioprotective activity specific for the germination process. These results further support the conclusion that gamma-radiation prevented germination by inducing (or maintaining) dormancy and preclude alternative explanations in terms of killing, mitotic inhibition, or general growth inhibition.