Influence of dimethyl sulfoxide on freezing resistance of lettuce seeds

DTA of lettuce seeds was used to study the cryoprotective mode of action of DMSO. Lettuce seeds were imbibed for 16 hr in 5, 10, 15 or 20% aqueous solutions of DMSO either with or without a 6 hr preimbibition in water. Seeds were frozen to postsecondary exotherm temperatures; exotherms were recorded; and germination was tested after freezing. DMSO had at least a twofold effect on the lettuce seeds: it increased the degree of supercooling, and it imparted a capacity to survive following freezing beyond secondary exotherm levels.