Hormonal Regulation of Seed Dormancy in Hazel (Corylus avellanaL.) and Beech (Fagus sylvaticaL.)

Dormancy in seeds of hazel (Corylus avellana L.) and beech (Fagus sylvatica L.) has been studied with special reference to changes in growth-promoting and inhibiting substances during after-ripening. About 12 weeks at low temperature and under moist conditions is necessary for complete after-ripening. Gibberellic acid, kinetin, and thiourea stimulate germination in dormant seeds but have no effect on nuts with the pericarp intact. Gibberellin ‘D’ is ten times more active than gibberellic acid. Bio-assays, following chromatographic fractionation of seed extracts, have revealed no significant changes in the concentrations of auxins and inhibitors during after-ripening. Dwarf maize-leaf section assays have revealed low concentrations of gibberellin-like substances in purified extracts of chilled, dormant hazel seed but no gibberellin activity in extracts of dormant seed. Gibberellins are present in both dormant and germinating beech seeds but there appear to be differences in the chromatographic pattern of activity. The possible role of endogenous gibberellins in the after-ripening process is discussed.