Agriculture Reference
In-Depth Information
understanding of the functions of rapidly increasing number
of genes involved in rice fl ower development. The genetic
framework of rice fl ower development is in part similar to
that of model edicots. However, rice also probably recruits
specifi c genetic mechanisms, which probably contribute to the
establishment of specifi c fl oral architecture of rice (Yoshida
and Nagato 2011).
The initiation of panicle primordium at the tip of the
growing shoot marks the start of the reproductive phase. The
panicle primordium becomes visible to the naked eye about
10 days after initiation. At this stage, 3 leaves will still emerge
before panicle fi nally emerges.
In short duration varieties the panicle becomes visible as
white feathery cone 1.0-1.5 mm long. It occurs fi rst in the main
culm and then in tillers where it emerges in uneven pattern.
The young panicle that emerges inside the bottom of the last
node is fi rst a little feathery cone shaped organ 1-1.5 mm, which
is visible only if the stem is dissected. In fact, the cone becomes
visible only about 10 days after it is formed. At this stage the
number of spikelets in the panicle is already determined.
In short duration varieties, maximum tillering, internode
elongation, and panicle initiation occur almost simultaneously.
These stages occur in the above mentioned order in medium
to long duration varieties. Timing of panicle initiation in rice is
infl uenced by many factors, among which some constants are
inherent to variety, temperature and photoperiod (Fig. 31).
Root growth measured as root length, is rapid and linear
during vegetative development of the rice plant. Maximum
root length is observed by panicle initiation or booting and is
maintained at nearly constant level until heading following
heading, root length declines until milk stage where it may
