Soluble sugars in light-sensitive Grand Rapids lettuce seeds treated with red light, gibberellic acid and a plant-derived smoke extract

The escape time for far-red light reversal of red light induced germination of light-sensitive Grand Rapids lettuce seeds was determined to be 5h. Levels of soluble sugars were determined during the first 8h of imbibition in seeds treated with red light, gibberellic acid and an aqueous smoke extract all of which stimulate germination of the photoblastic achenes in the dark. Sucrose was the main reserve sugar in the dry seeds; glucose, fructose and rhamnose were also detected. An increase in sucrose was detected 2h after the start of imbibition, lasting 13h. This increase occurred in all treatments, including dark-imbibed control seeds. This suggests that breaking of dormancy is not totally dependent on utilisation of soluble sugars