Induction of germination of skotodormant seeds of Johnson grass, Sorghum halepense (L.) Pers

Résumé: Zusammenfassung Germination of skotodormant (imbibed or redried dormant in the dark) seeds of Johnson grass [Sorghum halepense (L.) Pers.] is temperature dependent. There was better germination at 40°C than at lower temperatures. Alternating temperatures of 40/28 and 35/22°C were best, overall, for imbibed and re‐dried dormant seeds, respectively. For the imbibed, dormant seeds, there was apparent stimulation of germination by light, gibberelent A3 (GA3) and immersion in 700 mm sodium hypochlorite (NaOC1). However, the combinations of GA3+light, NaOC1+light, and NaOC1+GA3+light all had synergistic effects on the stimulation of germination of imbibed, dormant seeds. Germination of dry seeds treated with 900 min H2O2 was not affected, whereas the same treatment given to imbibed, dormant seeds resulted in about 40–60% germination. Stimulation of germination by H2O2 depends not only upon seed moisture content, but also upon concentration of H2O2 and previous NaOC1 immersion. Dry seeds immersed for 15 min in concentrated H2SO4 and incubated on water gave almost complete germination while no imbibed, dormant seeds germinated following this treatment. However, as little as 4 h of re‐drying of these imbibed, dormant seeds, prior to the same H2SO4 treatment, stimulated about 40% germination. It is suggested that the induction and breakage of skotodormancy in imbibed or re‐dried seeds in response to seasonal fluctuations in temperature and moisture may provide a survival mechanism for S. halepense. Induction de la germination des graines dormantes de Sorgho D'Alep, Sorghum halepense (L.) Pers. La germination de graines dormantes (imbibées ou ressechées à l'obscurité) de Sorgho d'Alep dépend de la température. La germination est meilleure à 40°C qu'à des températures plus basses. Des alternances de 40/28 et 35/22C étaient optimales respectivement pour les graines imbibées ou ressechées. Pour les imbibées, il y a une stimulation par la lumière, la gibberelline A3 (GA3) et l'immersion dans une solution 700 mm d'hypochlorite de sodium (NaOC1). Cependant, les combinaisons GA3+lumière; NaOC1+lumière, et NaOC1+GA3+lumière ont toutes des effets de synergisme de la stimulation de la germination des graines dormantes imbibées. La germination des graines sèches traitées avec une solution 900 mm de H2O2 n'est pas affectée tandis que le même traitement appliqué aux imbibées résulte dans 40 à 60%de germination des semences dormantes. La stimulation de la germination pour