Stimulation of Lettuce Seed Germination by 6-(Substituted) Purines

Presoaking several varieties of seed, especially lettuce, in various 6-(substituted)aminoand thiopur ine solutions has been found to increase their rate of germination (3, 5, 6). Recently it was also reported that these purine derivatives are synergistic with gibberellin in inducing these biological responses whereas gibberellin alone was only moderately active in stimulating germination of Early Curled Simpson lettuce seed (7, 8). The mode of biochemical action of these purine derivatives and gibberellin (2) in affecting the rate of germination is as yet unknown, although it has been observed that seed activation by white light is augmented by pretreatment of the seed with various 6-(substituted)purine solutions (6). Recently Miller (4) demonstrated that maximal purine-activation of Grand Rapids lettuce seed germination is somewhat dependent on the presence of light. The action spectrum for the influence of light on germination is not necessarily the same in the presence of 6-(substituted) purines as in their absence ( 1 ) ; far-red light initiates appreciable germination after pretreatment with kinetin, even though the far-red light is less effective than red light.