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Table Of Contents
TABLE OF
CONTENTS .........................................
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1
OVERVIEW AND
OBJECTIVES .......................................
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2
THREE GROWTH
PHASES
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2
GROWTH STAGES 0-9
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3
VEGETATIVE
PHASE
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8
Stage 0 - Germination to
emergence
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8
Stage 1 -
Seedling
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9
Stage 2 - Tillering
< br>.
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11
Stage 3 - Stem elongation
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14
REPRODUCTIVE PHASE
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17
Stage 4 - Panicle initiation to
booting
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17
Stage 5 -
Heading
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20
Flowering
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21
RIPENING PHASE
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24
Stage 7 - Milk
grain stage
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24
Stage 8 - Dough grain stage
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26
Stage 9 -
Mature grain stage
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27
PRINT VERSION
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29
PERIOD/GROWTH PHASES ..................
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1
Overview and Objectives
This reference guide discusses the
growth stages of the rice plant. The information
presented is
based on the data and
characteristics of IR64, a modern, high-yielding,
semidwarf variety, but
applies
generally to other rice varieties.
This reference guide will enable you
to:
?
recognize the 3 basic growth phases of
the rice plant and the stages of development in
each phase.
?
identify the growth stages of a rice
plant according to a 0-9 numerical scale. Each
number
in the scale corresponds to a
specific growth stage.
?
explain the specific physical changes
in a growing rice plant.
Three growth
phases
The growth of the rice plant is
divided into three phases:
1.
vegetative
(germination to panicle initiation);
2.
reproductive
(panicle
initiation to flowering); and
3.
ripening
(flowering to
mature grain)
?
?
?
In
the tropics, the reproductive phase is about 35
days and the ripening phase is about 30
days.
The differences in
growth duration are determined by changes in the
length of the
vegetative phase.
For example, IR64 which matures in 110
days has a 45-day vegetative phase, whereas
IR8 which matures in 130 days has a
65-day vegetative phase.
2
Growth stages 0-9
These 3
growth phases consist of a series of 10 distinct
stages. These stages are numbered and
described as follows:
Stage 0 is from germination to
emergence:
Stage 1 is called seedling:
3
Stage 2, tillering:
and Stage 3 is stem elongation:
4
These first 4 stages make
up the
vegetative phase
, the
first phase of rice plant growth.
Stage 4 is panicle initiation to
booting:
Stage 5 is heading or panicle
exsertion:
5
and Stage 6
is flowering:
Stages 4, 5, and 6 constitute the
reproductive phase
, the
second phase of rice growth.
6
Stage 7 is the milk grain stage:
Stage 8, the dough grain stage:
and Stage 9, the mature grain stage:
7
Stages 7 through 9
correspond to the
ripening
phase
, the last phase in the
development of the rice
plant.
Vegetative Phase
Stage 0 -
Germination to emergence
Seeds are usually pregerminated by
soaking for 24 hours and incubating for another 24
hours.
After pregermination the radicle
and plumule protrude through the hull.
8
By the second or third day after
seeding in the seedbed, the first leaf breaks
through the coleoptile.
The end of stage 0 shows the emerged
primary leaf still curled and an elongated
radicle.
Stage
1 - Seedling
The seedling
stage starts right after emergence and lasts until
just before the first tiller appears.
During this stage, seminal roots and up
to five leaves develop.
As the seedling continues to grow, two
more leaves develop. Leaves continue to develop at
the rate
of 1 every 3-4 days during the
early stage.
9
Secondary adventitious roots that form
the permanent fibrous root system rapidly replace
the
temporary radicle and seminal
roots.
This is an 18-day-old seedling ready
for transplanting. The seedling has 5 leaves and a
rapidly
developing root system.
10
Stage 2 -
Tillering
This stage extends
from the appearance of the first tiller until the
maximum tiller number is reached.
Tillers emerge
from the axiliary buds of the nodes and displace
the leaf as they grow and develop.
11
This seedling shows the position of the
two primary tillers with respect to the main culm
and its
leaves.
After
emerging, the primary tillers give rise to
secondary tillers. This occurs about 30 days after
transplanting.
12
The plant is now increasing in length
and tillering very actively. Here is a field with
plants at the early
tillering stage.
Note the tiller size and canopy development due to
increased leafing and tiller
development.
Besides numerous primary and secondary
tillers, new tertiary tillers arise from the
secondary tillers
as the plant grows
longer and larger.
13
By this stage, the tillers have
multiplied to the point that it is difficult to
pick out the main stem. Tillers
continuously develop as the plant
enters the next stage which is stem elongation.
Stage 3 - Stem
elongation
This stage may
begin before panicle initiation or it may occur
during the latter part of the tillering
stage. Thus, there may be an overlap of
stages 2 and 3.
14
The tillers continue to increase in
number and height, with no appreciable senescence
of leaves
noticeable. Ground cover and
canopy formation by the growing plants have
advanced.
Growth duration is significantly
related to stem elongation. Stem elongation is
more in varieties with
longer growth
duration. In this respect, rice varieties can be
categorized into two groups: the
short-
duration varieties which mature in 105-120 days
and the long-duration varieties which mature
in 150 days.
15