The root system of sorghum is extensive, and there are many root hairs.
An embryonic or primary root first appears upon germination.
Several such roots develop, these are not branched or are sparsely
branched. Secondary roots develop from the first node.
It is these roots that develop into the extensive root system of the
The primary roots subsequently die. Brace roots may appear later
on the lowermost nodes and may be numerous if the plant is unadapted.
These roots are not effective in uptake of water and nutrients.
The culm, or stem, is made up of a series of alternating nodes and
The stem is slender to very stout, measuring 0.5 to 5 cm in diameter
near the base, becoming narrower at the upper end, and varying in length
from 0.5 to 4m.
It is solid, with a hard cortex or rind and a softer pith. Vascular
bundles are scattered throughout the stem, but there are more near the
peripheral area, where they are so closely associated that they form
almost a solid ring.
The vascular bundles in the central portion of the stem are larger
than those at the periphery. The central bundles branch into leaf midribs,
while the peripheral bundles branch to form the smaller veins in the
The node appears as a ring at the base of the leaf sheath. This is
the point at which the leaf is attached to the stem.
A bud forms at each node except at the node to which the flag leaf
These buds, at successive nodes, arise on alternating sides of the
stem. At times these buds will develop to form axillary tillers. Basal
tillers if any, form at the first node.
Leaves are variously distributed along the stem in sorghum; in some
types they may be concentrated near the base, while in others they are
more or less uniformly distributed.
Leaves are borne at different angles to the stem, varying from almost
vertical to near-horizontal. Leaves may be as long as 1 m and may vary
in width from 10 to 15 cm.
The number of leaves vary greatly. In well-adapted plants there are
usually 14 to 17 leaves, but less adapted plants may have as many as
The leaves are borne alternately in two ranks along the stem, and
consist primarily of a sheath and a blade.
The sheath is attached to a node and surrounds the internode, and
frequently the node above it, before the blade extends outwards
Frequently, the sheaths attached to lower nodes will cover the nodes
above, but those higher on the plant will not extend as far as the node
The sheath is frequently covered with a waxy bloom; at times the bloom
is quite pronounced.
The blades are broad at the base and taper upward to a fine point;
they are glabrous, except on the inside just above the ligule and on
the outside near the junction with the sheath.
The margins of the leaf are smooth or scabrid, especially on the
upper half. The midrib is prominent, greenish or white, flattened or
slightly concave on the upper surface and convex on the lower one.
The blades are thicker at the base than at the tip and along the midrib
than along the margins.
There is a short (1 to 3 mm) membranous ligule at the junction of
the leaf blade with the sheath.
Leaves of the wild species are frequently long (30 to 75 cm) and
slender (0.5 to 7 cm in width).
The panicle may be short and compact or loose and open; 4 to 25 cm
or more long, and 2 to 20 cm or more wide.
The central axis of the panicle, the rachis, may be completely hidden
by the density of the panicle branches or completely exposed.
The rachis differs greatly in its shape and length-from long and thin
to short and stubby. The rachis may be striated hairy or glabrous and
divided into nodes and internodes.
Several branches are borne at each node. Primary branches or rays
arise at each node.
They are arranged in whorls. Rays branch and rebranch, final branches
Spikelet is unit of inflorescence. Spikelets occur in pairs.. One
spikelet is always fertile, sessile and the other is sterile and pedicellate
except the terminal sessile spikelet which is accompanied by two pediceled
The racemes vary in length according to the number of nodes and the
length of the internodes.
There are 1 to 4 nodes in some species, and 5 to 8 nodes in others;
internodes vary in length, thickness, and hairiness depending on the
Sessile Spikelets : The sessile spikelet varies in shape from lanceolate
to almost rotund and ovate and is sometimes depressed in the middle
and bears the grain.
The colour is green at flowering, changing to shades of straw, cream,
buff, yellow, red, brown, purple, or almost black at grain maturity.
Glumes vary from quite hairy to almost hairless. The lower glume is
usually somewhat flattened and conforms more or less to the shape of
the spikelet, while the upper one is more convex or boat shaped.
The seed may be enclosed by the glume or may protrude from it, being
just visible to almost completely exposed. There are two lemmas, each
a delicate white tissue.
The lower lemma is elliptic or oblong, about equal in length to the
glume. The upper lemma is shorter, more ovate, and may be awned. There
are also two lodicules and a palea, but these are much reduced.
Sorghum has two pistils and three stamens. Each fluffy stigma is attached
to a short stout style extending to the ovary. The anthers are attached
to long threadlike filaments.
Seed or Caryopsis: Seeds are more or less spherical in shape, varying
to somewhat flattened on one side (turtle-backed). They range tremendously
in pericarp color (red, brown, white, yellow, cream) and have either
a dull or pearly luster.
The testa may also be coloured, usually a dark red to dark brown.
The endosperm is usually white, though it may be yellow.
Pediceled Spikelets : These are much narrower than the sessile spikelets,
usually lanceolate in shape.
They may be smaller, the same size, or longer than the sessile spikelets.
They are male or neuter sex, but (very rarely) may have a rudimentary
The lemmas are much reduced in size and only rarely does the upper
lemma have an awn.
When a seed is placed in moist soil, it takes up water and swells.
Germination occurs quickly, the coleoptile first appears above the ground
after 3 or 4 days.
As the seed swells the seed coat breaks, and a small coleoptile and
primary root (radicle) emerge. The coleoptile grows longer and several
more primary roots appear.
The coleoptile begins to emerge from the ground, and the first leaf
breaks through the tip. The young plant begins to grow, adding more
leaves, and the coleoptile remains as a sheath at the base of the plant.
The mesocotyl grows during this period, and a node is formed at the
base of the coleoptile just below the ground line. Secondary roots begin
to develop from this node when the plant is 3 to 7 days from emergence.
The young seedling is using food stored in the endosperm during this
About the time the secondary roots have begun to develop, the mesocotyl
begins to die and the major root system develops from secondary or adventitious
roots. Some sorghums tiller profusely, especially the sudangrasses and
The grain sorghums vary in their capacity to tiller, but usually do
so only if there is adequate moisture or a poor stand.
In normally tillering varieties, tillers develop from adventitious
buds at the basal node soon after the secondary roots develop.
The plant remains in a vegetative phase for about 30 to 40 days, during
which all leaves are formed. After this period, growth occurs by cell
The floral initial forms 30 to 40 days after germination when the
plants are 50 to 75 cm tall. Floral initiation marks the end of the
vegetative growth due to meristematic activity.
Sorghum usually flowers in 55 to 70 days in warm climates, but flowering
may range from 30 to more than 100 days.
The sorghum head begins to flower at its tip and flowers successively
downward over a 4 or 5 day period.
Because all heads in a field do not flower at the same time, pollen
is usually available for a period of 10 to 15 days.
At the time of flowering, the glumes open and the three anthers fall
free, while the two stigmas protrude, each on a stiff style.
Flowering frequently occurs just before or just after sunrise, but
may be delayed on cloudy damp mornings.
The anthers dehisce when they are dry (but not in heavy dew or rain)
and pollen blows into the air.
Sorghum is primarily self pollinated (about 2 to 10% or more cross-pollination).
The pollen drifts to the stigma, where it germinates; the pollen tube,
with two nuclei, grows down the style, to fertilize the egg.
The glumes close shortly after pollination, though the empty anthers
and stigmas still protrude.
The ovule begins to develop as a light green, almost cream-coloured
sphere; after about 10 days it begins to increase in size and becomes
a darker green.
It takes about 30 days for the seeds to reach maximum dry weight (physiological
During this development, the seed passes through three stages : "milk",
"early dough" and "late dough".
The seeds contain about 30% moisture at physiological maturity; they
dry to about 10 to 15% moisture during the following 20 to 25 days.
The seed is ready for harvest at any time from physiological maturity
to seed dryness; however, seed with more than 12% moisture must be dried
Lower leaves begin to die and dry up during this period. By the time
the grain begins to dry, four or five of the lower leaves may dry up
and drop from the plant.
There is a distinct varietal difference in the rate of senescence
of remaining leaves.
All leaves may be dried, or almost dried, at grain maturity, or the
plant may remain green.
Eusorghum, which includes cultivated grain, syrup, fodder and broomcorn
varieties. The cultivated and wild grass sorghums are grouped under
subsection Arundinacea and johnsongrass and related 20 haploid chromosome
perennials, under subsection Halepensia.
Para-sorghum, includes the wild, grassy, 5-chromosome species in which
the upper sheath nodes are bearded. The Arundinaceae subsection has
Series a., Spontanea, includes the cultivated sudangrass and tunisgrass
together with some wild species of grass sorghum. The grain and sweet
sorghums are grouped into Series b., Sativa.
This series includes six sub series viz., Drummondii, Guineensia,
Nervosa, Bicoloria, Caffra, and Durra. Thirty-one species were described
within the six subseries.
Subseries I, Drummondii, includes the so-called "chicken corn" and
similar cultivated or wild types with long, slender, pointed, nearly
hairless glumes and with spikelets that often are deciduous, of the
species, S. aterrimum, S. drummondii and S. nitens.
Subseries II, Guineensia, includes the shallus and other types characterized
by glumes that spread open at maturity and with margins that usually
become involute. The kernels often change positions by turning, after
the glumes open. Many of the varieties grown in western and central
Africa show these characters, but the panicles are usually more compact
than the shallus and usually lack the yellow plant pigment that characterized
most shallus. The species are S. conspicuum, S. exertum, S. gambicum,
S. guineense, S. margaritiferum, S. mellitum, and S. roxburghii. The
roxburghii group includes the shallus and similar lax-panicled varieties.
Subseries III, Nervosa, includes S. nervosum the kaoliangs and the
"broom kaoliangs" S. membranaceum, S. basutorum, S. ankolib, S. melaleucum,
and S. spendidum are other types also having outer (lower) glumes that
are conspicuously striately nerved in the upper half.
Subseries IV, Bicoloria, varieties usually have obovate spickelets
with obscure nerves. Included are the broomcorns, many of the sorgos
and numerous grain sorghums. Important types are S. bicolor with stiff
panicle branches; S. dochna, with lax panicles and long adherent glumes,
which includes the broomcorns; and S. elegans with oblong or umbelliform
panicles. Other species are S. miliiforme, S. simulans, and S. motabile.
Subseries V, Caffra, includes varieties mostly with compact or mid-compact
panicles, and often with glumes almost as wide as long and that open
to expose 1/3 or more of the grain at maturity. This subseries includes
most of the kafirs and the hegaris (S. caffrorum); some sorgos; the
feteritas, and other types (S. caudatum) with large, dense panicles
and large rounded grains, S. nigricans with grains rounded at the tip
as in Suma sorgos. Other species are S. coriaceum and S. dulcicaule.
Subseries VI, Durra, includes types with broad spikelets bearing kernels
as long as, or longer than, the glumes. Most of the varieties have dense,
compact panicles. The types within this series are the durras S. durra
and S. subglabrescens, which include milos and other varieties with
a pronounced transverse wrinkle on the glume, S. cernuum which is somewhat
intermediate between the above types with a less pronounced transverse
wrinkle, and S. rigidum.