purple-flowered plants of impatiens balsamina maintained floral develo
pment on transfer from inductive short days (SD) to long days (LD), a
treatment in which red-flowered plants of Impatiens are known to rever
t to leaf production. An investigation into the nonreverting nature of
purple-flowered plants was carried out to establish whether these pla
nts achieved meristem commitment or whether their non-reverting state
was controlled by the leaves. When the leaves that had unfolded during
the inductive SD treatment were removed at the time of transfer to LD
, the purple-flowered plants did revert. This result suggests that, as
in red-flowered Impatiens, meristem commitment is absent, but that pu
rple-flowered plants maintain flowering in LD conditions because of a
more permanent supply of signal from their leaves than occurs in red-f
lowered plants. A working hypothesis is proposed to explain how a sign
al from the leaves can retain a controlling role during flower develop
ment.