A manual of rice seed health testing - IRRI books - International Rice ...

Morphology of the mature
plant
Mature plants of different varieties
vary in height from 1 to 5 m, depending
on heredity and environment.
Plants 1-2 m tall are common
for varieties grown in some ecosystems.
The mature plant (Fig. 2.2, 2.3)
is discussed below. (For further
reading, see Chang and Bardenas
1965, Vergara and Chang 1976, and
Vergara 1991.)
Root. Seminal roots disappear
quickly and are replaced by secondary
and adventitious roots which
develop at nodes both below and
above the ground. These roots
emerge in a whorl at the nodes
above the ground and can be seen at
maturity.
Culm. The rice plant’s culm (stem)
is composed of several nodes and
internodes. Leaves arise at the
nodes, with a bud in the axil. The
bud gives rise to a tiller. The
internodes are hollow or fistular,
with smooth outer surfaces, and
varying lengths. Lower internodes
are shorter and compressed near the
base, and are thick and solid. Tillers
arise alternately from the culm. Primary
tillers arise from the lowermost
nodes. In turn, they give rise to secondary
and tertiary tillers.
Leaves. The leaves are sessile and
are borne on the nodes. Each leaf
consists of a blade and a sheath. The
blades are flat and vary among varieties
in size, shape, color, angle of
insertion, and pubescence. The leaf
sheath envelopes the culm above the
node. The swelling at the base of the
leaf sheath is called the sheath
pulvinus and is often confused with
the node. The leaf associated with
thc panicle is called the flag leaf and
differs in shape from others. Veins
on the leaf are parallel and have a
prominent midrib. At the base of the
blade, on either side, are paired
small appendages called auricles.
Thcy may fall off in older leaves. The
place where the sheath and blade
join is called the collar or junctura.
Oh its inner junction is a membra-
2.2 Parts of a
primary and a
secondary tiller.
2.3 A mature rice
plant.
6 Rice seed health testing manual