RAPID INCREASES IN CYTOKININ CONCENTRATION IN LATERAL BUDS OF CHICKPEA (CICER-ARIETINUM L) DURING RELEASE OF APICAL DOMINANCE

We examined the role of cytokinins (CKs) in release of apical dominanc e in lateral buds of chickpea (Cicer arietinum L.). Shoot decapitation or application of CKs (benzyladenine, zeatin or dihydrozeatin) stimul ated rapid bud growth. Time-lapse video recording revealed growth init iation within 2 h of application of 200 pmol benzyladenine or within 3 h of decapitation. Endogenous CK content in buds changed little in th e first 2 h after shoot decapitation, but significantly increased by 6 h, somewhat later than the initiation of bud growth. The main elevate d CK was zeatin riboside, whose content per bud increased 7-fold by 6 h and 25-fold by 24 h. Lesser changes were found in amounts of zeatin and isopentenyl adenine CKs. We have yet to distinguish whether these CKs are imported from the roots via the xylem stream or are synthesise d in situ in the buds, but CKs may be part of an endogenous signal inv olved in lateral bud growth stimulation following shoot decapitation. To our knowledge, this is the first detailed report of CK levels in bu ds themselves during release of apical dominance.