Geographic variation and bud dormancy in beech seedlings (Fagus sylvatica L)

Italian populations of beech, originating from zones of similar altitudes but different latitudes (38 degrees 16'-43 degrees 49'N), were studied. The seedlings, 1 and 2 years old, were grown in Florence (43 degrees 45') under natural conditions or in climate-controlled chambers with short (SD) or long day (LD) after having been exposed, or not, to winter chilling (CH and NCH, respectively). Differences observed in precociousness of sprouting, thermal time, growth in length and duration of growing season all indicate a variation among the populations tied to the latitude of their zones of origin. Winter chilling was demonstrated to be the principal factor in the removal of dormancy in all the populations studied. In the northernmost populations a significant effect on sprouting was attributable also to photoperiodic regime. The interaction chilling x long day indicates that LD is able to partially substitute winter chilling and that once the need for removal of dormancy has been satisfied, temperature is presumably the principal environmental factor that controls sprouting.