Abstract: DifferentWelsh onion (A llium f istulosum L. ) varieties were used as materials to discuss the
relation between endogenous hormones and flower bud differentiation. The results showed that during the
p rocess of flower bud differentiation, the contents of abscisic acid (ABA) , gibberellin ( GA₃ ) and zeatin
( ZR) in the roots, cauloids and leaves ofWelsh onion peaked but indolylacetic acid ( IAA) decreased evi
dently when flower buds differentiation was basically comp leted, and the period of peak or valley of endoge
nous hormones appearing coincided with the time of flower bud differentiation comp leted, these indicating flow
er bud differentiation nearly connected with ABA, GA₃ , ZR and IAA. The contents and changing ranges of
endogenous hormones in different organs ofWelsh onion were significantly different, in which the contents and
changing ranges of ABA, GA₃ in leaves and ZR in roots were much more than that of the other organs, but
there was a little difference for that of IAA in roots and leaves. Further, ABA / IAA and ABA /GA₃ inWelsh
onion leaveswere obviously increasing along with the p rocess of flower bud differentiation, and peaked when
flower buds differentiation was basically comp leted, then decreased significantly, this illustrated the balance
between different endogenous hormones also p layed an important role in regulating and controlling flower bud
differentiation ofWelsh onion.

Key words: Welsh onion (Allium fistulosum L. ), Cultivation through winter, Flower bud differentiation, Endogenous hormone