The effect of cold treatment during seed imbibition on lettuce radicle length and the uniformity of seedling emergence

SUMMARY Two experiments were conducted to determine how a period of exposure to 0 o C, between two periods of imbibition at 20 o C, affected radicle development and the uniformity of seedling emergence. In both experiments cold treatments, given 12 h after seed imbibition began, produced shorter radicles than those given at 0, 4, 8, 16 and 20 h. Increasing the duration of exposure to 0 o C gave longer radicles and reduced the spread of seedling emergence. It is concluded that lettuce seeds are particularly sensitive to a temperature change about 12 h after seed imbibition starts.