Induction of Flowering in Wild Lettuce (Lactuca Serriola L.)

SUMMARY Both seed and rosettes of Lactuca serriola L. are naturally vernalized during the winter. The response, measured by reduction in time required to flower, is greatest following vernalization of seed and declines with increasing age of the vegetative rosette. However, seedlings pass through a phase of minimum response to vernalization in the cotyledon stage (52% of seed response) after which it increases (73% at two‐leaf stage) before declining in older rosettes. The significance of the effect of stage of development at the start of vernalization is discussed in relation to control of phenology in the natural environment. Effects of photoperiod and temperature on induction of flowering are considered and comparison made with L. sativa.