Yoshida - 1981 - Fundamentals of Rice Crop Science

52 FUNDAMENTALS OF RICE CROP SCIENCE
Table 1.13. Duration of each development stage for a panicle
or a spikelet. a
Developmental stages b
Duration (days)
1953 c 1954 d
Differentiating stage of the neck node 2.0 2.0
Increasing of bracts stage 1.0 1.0
Duration of differentiation
of bracts 3.0 3.0
Early differentiating stage of
primary rachis-branches 1.5 1.0
Middle differentiating stage of
primary rachis-branches 2.0 2.0
Late differentiating stage of
primary rachis-branches 2.2 1.0
Duration of differentiating stage
of primary rachis-branches 5.7 4.0
Early differentiating stage of
secondary rachis-branches 1.2 1.0
Late differentiating stage of
secondary rachis-branches 2.0 1.5
Duration of differentiating of
secondary rachis-branches 3.2 2.5
Initial stage of spikelet
differentiation 1.0 1.0
Early differentiating stage
of spikelets 3.0 3.0
Middle differentiating stage
of spikelets 1.0 1.2
Late differentiating stage
of spikelets 4.0 3.2
Duration of differentiation
of spikelets 9.0 8.4
Differentiating stage of pollen
mother cell 2.5 1.8
Reduction division stage 2.0 1.8
Early stage of extine formation 1.2 1.6
Extine formation stage 3.3 2.5
Early ripe stage of pollen 2.0 2.0
Ripe stage of pollen 5.5 5.0
Total 37.4 32.6
a Matsushima (1970). b The topmost spikelets were used. c Unusual
weather. d Normal weather.
For example, when a 14-leaf and a 18-leaf variety have developed 6 leaves on the
main culm, their leaf number indexes are 43 and 33, respectively.
The leaf number indexes ate related to the developmental stages of a growing
panicle (Table 1.14). Such relationship holds only for terminal spikelets and for
16-leaf varieties. The neck-node differentiation occurs when the leaf number
index is around 77, or when the plant has developed 12.3 leaves. The spikelet
differentiation stage comes at a leaf number index of around 90, or when the plant
has 14.4 leaves.