| Lettuce germination is strongly dependent on the temperature of imbibition and subject to complex hormonal and developmental regulation. The objective of this research was to establish the role of ethylene in germination of thermosensitive ‘Dark Green Boston’ and thermotolerant ‘Everglades’ seeds at supraoptimal temperatures, in continuous light and dark. In order to achieve the research objective, the ethylene action inhibitor silver thiosulfate and the ethylene precursor, 1-aminocyclopropane-l-carboxylic acid, were applied to ‘Dark Green Boston’ and ‘Everglades’ seeds, and germination of transgenic lettuce lines with reduced ethylene perception or altered ethylene biosynthesis as well as seeds matured at elevated temperatures was examined. Germination of ‘Dark Green Boston’ seeds was stronger inhibited by silver thiosulfate than ‘Everglades’ germination. Silver thiosulfate was more effective in reducing germination at supraoptimal temperatures than at optimal temperatures. Maturation of ‘Dark Green Boston’ and ‘Everglades’ seeds at elevated temperatures (30°/20°C) led to increased ethylene production, and consequently, germination as compared to seeds matured at 20°/10°C. Imbibition in dark led to reduced ethylene production as compared to light. Application of 1-aminocyclopropane-1-carboxylic acid increased germination of seeds matured at 20°/10°C in light to the level of 30°/20°C germination. ‘Dark Green Boston’ seeds with reduced ethylene perception were more thermosensitive than wild-type ‘Dark Green Boston’ seeds. ‘Everglades’ seeds with reduced ethylene perception had similar germination to wild-type ‘Everglades’ seeds at optimal temperature in light and dark and at supraoptimal temperature in light. At supraoptimal temperature, in dark, their germination was significantly reduced as compared to wild type ‘Everglades’ germination. The results of the research indicated that the ability of lettuce seeds to germinate at supraoptimal temperatures was dependent on the ethylene production and was reduced if sensitivity to ethylene was decreased. |
