A few studies have pointed out the
involvement of CKs with floral transition, acting
as a signaling component of the process (Bernier et
al., 1993; Kinet et al., 1993). The data showed that
in the samples taken 5 d after transfer to the
flowering inductive medium (1.8 mM TDZ) the total
endogenous CK level of the explants reached a
maximum value (Fig. 1A), which was mainly due to
higher levels of [9R]iP, [9R]Z and Z (Fig. 1B). A
second increase in total CKs (5 d before flower buds
were first visible) was detected in the samples
taken at day 25, although not as pronounced as the
first one; [9R]iP accounted for most of this
increase. From 25 to 40 d of culture [9R]iP levels
did not exhibit a significant variation while the
other CKs dropped to levels relatively similar to
those detected in the control treatment. The total
endogenous CKs of the shoots in the non-inductive
medium remained relatively constant throughout
the collecting period (Fig. 1C).