The effect of cold storing pre‐germinated lettuce seeds on radicle development and seedling emergence

SUMMARY The effects on radicle development and seedling emergence of cold storing batches of pre‐germinated lettuce seeds for up to 7 days at 0 or 2 °C were investigated in three experiments. Cold storage tended to delay emergence and increase its spread in time. Separate batches of pre‐germinated seeds gave different mean radicle lengths and different patterns of emergence and it is likely that small differences in mean temperature during germination were responsible since the length of radicles after germination was linearly related to accumulated day‐degrees during the germination period. This suggests that germinating seeds over a period during which a required number of day‐degrees is accumulated may produce radicles of the same length for different sowings. The elongation of radicles during cold storage was also linearly related to accumulated day‐degrees. At 2 °C it appeared that the longer radicles elongated faster than the smaller ones and this may account for cold storage tending to increase the spread of seedling emergence when the pre‐germinated seeds were sown into compost.