J. Wyman et al., CELL-CYCLE ACTIVATION DURING IMBIBITION AND VISIBLE GERMINATION IN EMBRYOS AND MEGAGAMETOPHYTES OF JACK PINE (PINUS-BANKSIANA LAMB), Annals of botany, 78(2), 1996, pp. 245-253
Flow cytometric determination of cell cycle activation during imbibiti
on and visible germination in Five families of jack pine (Pinus banksi
ana Lamb.) embryos and megagametophytes revealed that in seeds that ha
d undergone no imbibition the majority of cells were in the 2C state.
As the imbibition period increased, less of the nuclei were blocked in
the G0/G1 state and more become active in the cell cycle. The augment
ation in the nuclei active in the 2C-4C cycle as well as those with DN
A levels higher than the 4C state occured gradually and preceeded radi
cle emergence. In megagametophyte tissue examined at various stages of
imbibition, cell cycle activity became apparent rapidly following imb
ibition. In nuclei of green and white embryos examined separately the
chi(2) frequency distributions were significantly different for all th
ree families after 144 h. As imbibition period increased, fewer nuclei
from the green embryos were blocked in the 2C state, and more became
active in the 2C-4C cell cycle. This was not the case for white embryo
s where no significant linear relation was noted. Cell cycle activity
in the hypocotyl + cotyledons region and the emerging radicle were exa
mined separately. Functional relations found in the hypocotyl + cotyle
dons region were not evident in the radicle. As visible germination pr
oceeded, cell cycle activity in the hypocotyl + cotyledons region for
this period of germination showed a reversal of the activity noted dur
ing imbibition: Fewer nuclei were active and once again a higher propo
rtion were found in the 2C state. (C) 1996 Annals of Botany Company