2
Botanical Aspects of Cereals
Grasses
Cereals are cultivated grasses that grow through-
out the temperate and tropical regions of the
world. As members of the Gramineae (or grass
family) they share the following characteristics,
but these are developed to different degrees in
the various members:
Vegetative features of grasses
1. Conspicuous nodes in the stem.
2. A single leaf at each node.
3. Leaves in two opposite ranks.
4. Leaves consist of sheath and blade.
5. Tendency to form branches at nodes and
adventitious roots at the bases of nodes.
6. Lower branches may take root and develop
into stems as tillers.
Variation in vegetative features among species
may be illustrated by reference to maize and
wheat. In wheat branches occur only at the base
of the main stem or culm, to produce tillers (Fig.
2.1) (Percival, 1921). While all tillers have the
capacity to bear ears, the later formed ones may
not actually do so; this habit is characteristic of
most cereals.
In maize branches occur higher on the main
stems and they are much shorter as the internodes
do not extend (Fig. 2.2).
Leaf bases are very close together and the leaves
consist almost entirely of blades which surround
the inflorescence, and the shortness of its stalk
leads to branches that are almost entirely inflore-
scence. At the tip of the main culm there is also
an inflorescence as in wheat, but maize is unique
FIG 2.1 The pattern of branching
in the wheat plant.
FIG 2.2 The
pattern of
branching
in the maize
plant
among cereals in that, on the branches, only the
female organs develop in the florets and on the
main culm only male organs develop. The advent-
itious roots that develop at the base of the main
stem provide support for the aerial parts of the
plant (Ennos, 1991); in maize they are called
prop-roots and they are particularly well developed
as is appropriate to the large and heavy nature of
the aerial parts.
29
30 TECHNOLOGY OF CEREALS
Reproductive features of grasses
1. All stems and branches normally form terminal
2. Flowers are produced in spikelets.
3. Each flower is enclosed between two bracts,
the lemma and palea (pales or flowering
glumes).
4. At the base of each spikelet are two glumes
(empty or sterile glumes).
All cereal inflorescences are branched structures
but the type of branching varies. The loose
spreading structure found in oats is known as a
panicle (Fig. 2.3).
The main axis of the panicle, the peduncle,
bears several extended branches on which the
spikelets are attached through short stalks or
pedicels. Within the spikelet florets alternate
(Fig. 2.4); the two closest to the base are similar
in size but florets become progressively smaller
towards the tip.
Each floret (Fig. 2.5) contains the female
organs, a carpel containing a single ovule, with
its stigma; and the male parts, three stamens,
each consisting of filament and anther. Pollen
released from the anthers, which split when ripe,
is transferred by wind to the receptive stigma on
another plant. The elaborate feathery style has
an extensive sticky surface well suited to intercept-
ing wind-borne pollen. Before the anthers mature,
the time of flowering or ‘anthesis’ the pales are
forced open by the expansion of organs called
lodicules at their base (lodicules swell as a result
of an influx of water). The filaments of the
stamens rapidly extend, projecting the opening
anthers outside the pales, allowing the pollen to
be shed onto the wind.
Rice inflorescences are also panicles but spike-
lets contain only one floret. Glumes are mostly
insignificant small scales. Rice florets are unlike
those of other cereals in having six stamens. (Fig.
2.6)
In sorghum the situation is complex: inflore-
scences are panicles but they may be compact or
open (Hulse et al., 1980). Spikelets occur in pairs,
One is sessi1e and the Other borne On a short
pedicel. The sessile spikelet contains two florets,
inflorescences.
FIG 2.3 The oat panicle. Reproduced from Poehlman (1987)
by courtesy of Avi publishers, New yo&.
Rudimentary tertiary floret
they remain enclosed between the pales but at
ned primary floret
f‘oret
FIG 2.4 Spikelet of oat. Reproduced from Poehlman (1987)
by courtesy of Avi Publishers, New York.
BOTANICAL ASPECTS OF CEREALS 31
Poehlman (1987) by courtesy of Avi Publishers, New York.
Sterile spikelet Fertile spikelet
FIG 2.7 A pair of spikelets of sorghum. Reproduced from
Poehlman (1987) by courtesy of Avi Publishers, New York.
FIG 2.6 Reproductive organs of a rice floret. Note the six
stamens present. Reproduced from Poehlman (1987) courtesy
of Avi Publishers, New York.
one perfect and fertile and the other sterile. The
pedicelled spikelet is either sterile or develops
male organs only (Fig. 2.7).
In barley the type of inflorescence is a spike
(Fig. 2.8).
It is more compact than a panicle, the spikelets
being attached to the main axis or rachis by much
shorter rachillas. The rachis is flattened and
adopts a zigzag form, spikelets occur in groups
of three alternately on the rachis. In six-rowed
types all spikelets develop to maturity and each
bears a grain in its single floret. In two-rowed
types only the central spikelet in each three
develops in this way; the others are sterile. The
glumes are very small but the pales fully surround
the grain and remain closely adherent to it even
after threshing. The lemma tapers to a long awn
which does break off during threshing. Many
variants of the barley spike are illustrated by
Briggs (1978).
The inflorescences of wheat, rye and triticale
FIG 2.8 Spikes of barley, showing: a. the two-rowed and b.
the six-rowed forms.
32 TECHNOLOGY OF CEREALS
FIG 2.9 Spikes of A. wheat and B. rye. Wheat may be awned (bearded) (ii) or awnless (i).
are also spikes with spikelets alternating on a are many different species belonging to several
rachis, each spikelet however contains up to six different tribes (see Fig. 2.25) and no generaliza-
florets (Fig. 2.9). tions about their inflorescences are possible (details
It is unusual for all six florets in a spikelet to of most are given in Hulse et al., 1980.) Pearl
be fertile and those at the extremes of the millet has a spike which may be anything between
inflorescence may bear only one or even no fertile a few centimeters to a metre long. It is densely
florets. Variants of wheat spikes are illustrated packed with groups of 2-5 spikelets, surrounded
by Peterson (1965). As in oats the grains in the by 30-40 bristles (Fig. 2.11). Florets may be
two basal florets are the largest. Those in the bisexual or male only.
centre of the spike are larger than those at In maize the male spikes occurring at the top
the extremes (Bremner and Rawson, 1978). The of the culm bear spikelets in pairs, one being
variation in size occurs as a function of the ability sessile, and the other pedicellate. Both types
of each grain to compete for nutrients but also contain two florets, each with three anthers. The
of the period of development, the earliest to entire male inflorescence is known as the tassel
flower being those in the basal florets of the (Fig. 2.2). On the female inflorescences the
central spikelets (Fig. 2.10). spikelets again carry two florets but only one is
fertile, the upper functions while the lower one Millets are an extremely diverse group, there
j_
c
II
tl8-
g 9-
* 2 1 w a 10 12 11
0-l 14 15 13-
16 17
ie 19
20
I-
**
% \* (b)
- \e ‘It \.4
- 7) *i;
7- A\A \*
\+ A \‘*\
- +/:,a -
- f J1 */
I I
30 40 50 60
34 TECHNOLOGY OF CEREALS
FIG 2.12 Radial section of a maize cob, showing (i) a perfect
(fertile) and (ii) a rudimentary (empty) floret. Based on
A. L. and K. B. Winton (1932).
Nevertheless the quality of the grain is dependent
upon the condition of the plant; diseases that
affect the leaves, roots and stem can reduce the
photosynthetic area, the ability of the plant to take
up water and nutrients from the soil, and the ability
of the plant to stand. Agricultural scientists have,
through experimentation, determined the optimal
times for field treatments such as fertilizer, herbi-
cide and pesticide applications. For communicating
this information it has been found convenient to
define stages of plant growth and several scales
have been devized. Those that exist for wheat,
barley and oats have been compared by Landes
and Porter (1989). The decimal scale of Zadoks
et al. (1974) is illustrated here (Fig. 2.14).
Scales usually start at the time of seed germina-
tion but a life cycle is, by definition, a continuously
repeating sequence of events and, as such, has no
absolute beginning or end.
The beginning of each new generation occurs
when pollination is effected. As in all plants this
results when pollen produced in the anther con-
tacts the stigma on the carpel of another, or even
FIG 2.13 Cob of maize, showing the protective husk.
the same floret. Once on the stigma, pollen grains
have a mechanism whereby a pollen tube is
produced. The tube progresses towards the micro-
pyle and, having effected access by this route, it
allows nuclei from the pollen grain to pass into
the ovule and fuse with nuclei present there. The
primary fusion is of the sperm nucleus with the
egg nucleus. The product is a cell, the successive
divisions of which produce the embryo. A further
set of fusions, however, produces the first endo-
sperm nucleus. Three, not two, nuclei are involved,
one from the pollen and two polar nuclei from the
36 TECHNOLOGY OF CEREALS
germination vary with uses. In grains destined
for malting the requirement is for ready and
vigorous germination as soon after harvest as
possible but this must be combined with resistance
to sprouting, Or Premature germination Prior to
harvest. Resistance to sprouting is, in fact, desir-
able in all cereals, irrespective of their intended
use, because the growth of the embryonic axis is
accompanied by the production of hydrolytic
enzymes which render stored nutrients in the
endosperm soluble, thus reducing the amount of
starch and protein harvested. Additionally the
presence of high germination enzyme levels 5. Testa or seedcoat.
in cereals intended for flour production gives
rise to excessive hydrolysis during processing.
Bread-making flours are particularly sensitive
to such high enzyme levels as processing con-
ditions are well suited to enzyme-catalyzed
hydrolysis.
Germination is a complex syndrome, the details
of which are not fully understood. The important
events are shown in the flow diagram (Fig. 2.15)
below.
caryopsis), which is a type of achene. All achenes
are dry (rather than fleshy like many common
fruits). All fruits, whether dry or fleshy, typically
contain one or more seeds. In the case of caryopses
the number of fruits contained is one, and the
seed accounts for the greater part of the entire
fruit when mature. It comprises:
1. Embryonic axis;
2. Scutellum;
3. Endosperm;
4. Nucellus;
Starchy endosperm
Grain anatomy
The basic structural form of cereal caryopses
is surprisingly consistent, to the extent that a
‘generalized’ cereal grain can be described (Fig.
FIG 2.16 Generalized cereal grain, showing the relationships
among the tissues. The proportions that they contribute, in
individual cereals, are shown in Table 2.1.
2.16).
Although frequently referred to as seeds, cereal
grains are in botanical terms fruits. The fruits
of grasses are classified as caryopses (singular:
Embryo
The embryonic axis and the scutellum together
constitute the embryo. The embryonic axis is the
plant of the next generation. It consists of pri-
mordial roots and shoot with leaf initials. It is
connected to and couched in the shield-like scutel-
lum, which lies between it and the endosperm.
There is some confusion about the terminology
of the embryo as the term ‘germ’ is also used by
cereal chemists to describe part or all of the
embryo. If the botanical description is adopted
as above and ‘germ’ reserved for the embryo-rich
fraction produced during milling, then there can
be no confusion.
The scutellum behaves as a secretory and
Wote. Yxygen
Resting grain
If dormant
no change iw
ErnbryJ Horrnones 7
1 t L K%j~~r!hes’s
Growth of roots
and shoots
Solublllzatlon of cell walls,
proteins and starch
FIG 2.15 The main events involved in germination of a
seed.
BOTANICAL ASPECTS OF CEREALS
37
p
A
SA
FIG 2.17 Part of a transverse section of a grain of Hard Red Winter wheat, 14.4% protein content,
showing concentration of protein in subaleurone endosperm. Protein concentration diminshes towards
the central parts of the grain in all cereals. P, pericarp; A, aleurone layer; SA, subaleurone endosperm;
I, inner endosperm. (Reproduced from N. L. Kent, Cereal Chem. 1966,43: 5'85, by courtesy of the
Editor.)
Although the fusions of nuclei, occurring dur-
ing sexual fertilization, and leading to the forma-
tion of endosperm and embryo respectively, take
place approximately at the same time, the develop-
ment of the embryo tissue, by cell division, is
relatively delayed. When the embryo does enlarge,
it compresses the adjacent starchy endosperm
tissue giving rise to a few layers of crushed, empty
cells the contents of which have either been
resorbed or have failed to develop. The crushed
cells are described variously as the cementing,
depleted or fibrous layer .
absorptive organ, serving the requirements of
the embryonic axis when germination occurs.
It consists mainly of parenchymatous cells, each
containing nucleus, dense cytoplasm and oil
bodies or spherosomes. The layer of cells adja-
cent to the starchy endosperm consists of an
epithelium of elongated columnar cells arranged
as a pallisade. Cells are joined only near their
bases.
Exchange of water and solutes between scutel-
lum and starchy endosperm is extremely rapid.
Secretion of hormones and enzymes and absorp-
tion of solubilized nutrients occurs across this
boundary during germination. The embryonic
axis is well supplied with conducting tissues of a
simple type and some conducting tissues are also
present in the scutellum (Swift and O'Brien, 1970).
Endosperm
The endosperm is the largest tissue of the grain .
It comprises two components that are clearly
38 TECHNOLOGY OF CEREALS
distinguished. The majority, a central mass des-
cribed as starchy endosperm, consists of cells
packed with nutrients that can be mobilized to
support growth of the embryonic axis at the
onset of germination. Nutrients are stored in
insoluble form, the major component being the
carbohydrate starch. Next in order of abundance
is protein. In all cereals there is an inverse
gradient involving these two components, the
protein percentage per unit mass of endosperm
tissue increasing towards the periphery (Fig.
2.17).
Cell size also diminishes towards the outside
and this is accompanied by increasing cell wall
thickness. The walls of the starchy endosperm of
wheat are composed mainly of arabinoxylans,
while in barley and oats (1-3) and (1-4) p-D
glucans predominate. Cellulose contributes little
to cereal endosperm walls except in the case of
rice (see p. 64).
Surrounding the starchy endosperm is the
other endosperm tissue, the aleurone, consisting
of one to three layers of thick-walled cells with
dense contents and prominent nuclei.
The number of layers present is characteristic
of the cereal species, wheat, rye, oats, maize and
sorghum having one and barley and rice having
three. Unlike the tissue they surround, aleurone
cells contain no starch but they have a high
protein content and they are rich in lipid. They
are extremely important in both grain deve-
lopment, during which they divide to produce
starchy endosperm cells, and germination, when
in most species they are a site of synthesis of
hydrolytic enzymes responsible for solubilizing
the reserves.
The balance between aleurone and scutellum
in the latter role varies among species. Both
tissues synthesize the enzymes in response to
hormones including giberellic acid, transmitted
from the embryonic axis (via the scutellum in the
case of the aleurone). A further function of
aleurone cells in some millets and sorghum is the
transfer of metabolites into the starchy endo-
sperm during grain maturation. This activity is
deduced from the knobbly, irregular thickenings
on their walls often associated with such transfers
(Rost and Lersten, 1970).
At maturity the starchy endosperm dies but
aleurone cells continue to respire, albeit at a
very slow rate, for long periods. The aleurone
tissue covers the outer surface of the embryo but
its cells in this area may become separated and
degenerate. Their ability to respire and to pro-
duce enzymes on germination is in some doubt
(Briggs, 1978).
Seed coats
Surrounding the endosperm and embryo lie the
remains of the nucellus, the body within the ovule
in which the cavity known as the embryo sac
develops. Following fertilization the embryo and
endosperm expand at the expense of the nucellus,
which is broken down except for a few remnants
of tissue and a single layer of squashed empty
cells from the nucellar epidermis. Epidermal cells
in many higher plants secrete a cuticle and a
cuticle is present on the outer surface of the
nucellar epidermis of many cereals.
The outermost tissue of the seed is the testa or
seed coat (the nucellar epidermis is also regarded
as a seed coat but its origin is different from that
of the testa which develops from the integuments).
The testa may consist of one or two cellular layers.
In some varieties of sorghum a testa is absent
altogether. Where two layers are present the long
axes of their elongated cells lie at approximately
90" to each other. Frequently the testa accumulates
corky substances in its cells during grain ripening
and this may confer colour on the grain and
certainly reduces the permeability of the testa. A
cuticle, thicker than that of the nucellar epidermis,
is typical, and this also plays a role in regulating
water and gaseous exchange.
Both testa and nucellus are tissues which once
formed part of the ovule of the mother plant.
They are thus of an earlier generation than the
endosperm and embryo which they surround and
to which they closely adhere.
Pericarp
The pericarp (or fruitcoat) is a multilayered
structure consisting of several complete and in-
complete layers. In all cereal grains the pericarp
BOTANICAL ASPECTS OF CEREALS 39
tube cells that contain chloroplasts in the immature
green grain. The ‘mesocarp’, outside the cross
cells, is not found as a true layer in mature grains
except in sorghums. It is in this pericarp tissue
that starch accumulates during grain maturation,
but in most cases becomes reabsorbed before
maturity.
The outermost layer of the pericarp and indeed
of the caryopsis is the outer epidermis or ‘epicarp’;
it is one cell thick. It is adherent to the ‘hypodermis’
which may be virtually absent, as in oats or some
millets, one or two layers thick, as in wheat, rye,
sorghums and pearl millet or several layers thick,
as in maize. The outer epidermis has a cuticle
which controls water relations in growing grains
but generally becomes leaky on drying (Radley,
1976). Hairs or trichomes are present at the
nonembryo end of wheat, rye, barley, triticale
and oats. They are collectively known as the
‘brush’ and they have a high silicon content.
Trichomes have a spiral sculptured surface that
is dry at maturity consisting of largely empty
cells. During development it serves to protect and
support the growing endosperm and embryo. At
this time chloroplasts are present in the innermost
layers and starch accumulates as small granules
in the central layers. By maturity all starch has
disappeared and the cells in which it was present
are largely squashed or broken down. An excep-
tion to this is provided by some types of sorghum
in which at least some of the cells and some of
the starch granules persist.
The innermost layer of the pericarp is the inner
epidermis or epicarp. In many cereals this is an
incomplete layer. Its cells are elongate and thus
termed ‘tube cells’. They are sometimes squashed
flat in mature grains. Outside this layer lies the
‘cross cell layer’. Unique to grasses, this layer
takes its name from the fact that the long axes of
its elongate cells lie at right angles to the grain’s
long axis. They are arranged side by side, in rows,
in wheat, rye and barley. It is the cross cells and
TABLE 2.1
Proportions of Parts of Cereal Grains (%)
Embryo
Pericarp and Starchy Embryonic
Cereal Hull testa Aleurone endosperm axis Scutellum
Wheat
Thatcher - 8.2 6.7 81.5 1.6 2.0
Vilmorin 27 - 8.0 7.0 82.5 1 .o 1.5
Argentinian - 9.5 6.4 81.4 1.3 1.4
Egyptian 7.4 6.7 84.1 1.3 1.5
Barley
Whole grain 13 2.9 4.8 76.2 1.7 1.3
Caryopsis - 3.3 5.5 87.6 1.9 1.5
Whole grain 25 9.0 63.0 1.2 1.6
Caryopsis (groat) - 12.0 84.0 1.6 2.1
Rye - 10.0 86.5 1.8 1.7
Rice Y-
Whole grain 20 4.8 73.0 2.2
Indian - 7.0 90.7 p .9 1.4,
Egyptian - 5.0 91.7 313
Oats “
I
Caryopsis
Sorghum - 7.9 82.3 9.8
Maize
Flint - 6.5 79.6 1.1 10.6
Sweet - 5.1 ,::: 8l 76.4 -2.0 13.2,
Dent - 6 1 2“
Proso millet 16 3 6.0 70 5
Sources as in Kent (1983).
40 TECHNOLOGY OF CEREALS
differs among cereals allowing their origin to be
determined when they are found detached from Maze Rye Wheat Sorghum M"let Ragi
the grain (Bennett and Parry, 1981).
The tissues described above are present in
cereal grains even if they are of the naked or
free threshing type. In some cereal grains, such
as oats, barley, rice and some millets, the pales
are closely adherent and are thus not removed by
threshing. These are therefore part of the grain
as traded and their additional contribution to
grain mass has to be borne in mind when compar- Barley Oats Rice Barley Oat Rice
ing the relative proportions of nutrients in different caryopsis (groat) caryopsis
species (Table 2.1).
00"
@Q8
Covered grain
01 (a80
? 7 1,O mm
Grain characteristics of individual FIG 2.18 Grains of cereals showing comparative sizes and
shapes. The caryopses of the three husked grains (barley,
oats, rice) are shown with and without their surrounding
pales.
side to the embryo. At the inner margin of the
crease there lies between the testa and the endo-
sperm, a column of nucellar tissue (Fig. 2.19).
Whereas elsewhere in the grain the nucellar
epidermis is all that remains of that tissue, several
layers of parenchymatous cells persist to maturity
in the crease. They carry the remains of vascular
tissue by which nutrients were transported into
the developing grain and it is likely that their
final passage into the endosperm was via the
nucellar cells.
cereals
In spite of structural similarities, there are wide
variations among cereal grains in size and shape.
Comparisons in size and form are shown diagram-
matically in Fig. 2.18, and mass differences are
given in Table 2.2.
Wheat
Wheat exhibits few differences from the general-
ized structure described (Fig. 2.16). Its most
striking morphological characteristic is a crease
or elongated re-entrant region parallel to its long
axis, and on the ventral side - that is the opposite
TABLE 2.2
Dimenstons and Wezght per 1000 Grains of the Cereals
Dimensions Weight per 1000 (grains)
Length Width Average Range
Cereal (mm) (mm) (g) (g)
Millets
Teff 0.14-0.2
Proso 6
Pearl 2 1.C2.5 7 5-10
AY e 4.j-iG i.5-3,j 2i - i 346
Rice 5-10 1.5-5 27
Oats 6-13 1.04.5 32
Triticale 36 28-45
Barley 8-14 1.04.5 35 32-36
Wheat 5-8 2.5-4.5 37
Maize 8-17 5-15 324
-
Sorghum 3-5 2-5 28 8-50
CWRS:27
English:48
150-600
i
Source: Kent (1983).
BOTANICAL ASPECTS OF CEREALS 41
vides the best collection of detailed descriptions
of cereal tissues).
Among cereals wheat has a relatively high
protein content in the starchy endosperm (say 8-
16%). Two distinct populations of starch granules
are present, two thirds of the starch mass being
contributed by large lenticular granules between
8 and 30 pm and one third by near-spherical
granules of less than 8 pm diameter (see Ch. 3).
p
\
starchy
endosperm
-
Rye
Rye grains are more slender and pointed than
wheat grains but they also have a crease and
indeed share many of the features described for
wheat. The beadlike appearance of the cell walls
of the pericarp is less distinct than in wheat. Rye
grains may exibit a blue-green cast due to pigment
present in the aleurone cell contents. Two popula-
tions of starch granules are present as in wheat;
the larger granules, seen under the microscope,
often display an internal crack.
Barley
Barley grains mostly have a hull of adherent
pales which is removable only with difficulty. It
amounts to about 13% of the grain (by weight)
on average, the proportion ranging from 7 to 25%
according to type, variety, grain size and latitude
where the barley is grown. Winter barleys have
more hull than spring types: six-row (12.5%)
more than two-row (10.4%). The proportion of hull
increases as the latitude of cultivation approaches
the equator, e.g. 7-8% in Sweden, 8-9% in
France, 13-14% in Tunisia. Large and heavy
grains have proportionately less hull than small,
lightweight grains.
Grains are generally larger and more pointed
than wheat though they are not less broad. They
have a ventral crease which is shallower than those
of wheat and rye and its presence is obscured by
the adherent palea. Cross cells are in a double
layer and their walls do not appear beaded. Only
one cellular testa layer is present. Two to four
(mostly three) aleurone layers are present, cells
being smaller than those in wheat; about 30 pm
in each direction. Blue colour may be present due
A aleurone 0 pigment strand
C nucellar epidermis F conducting tissue
B nucellar projection E crass cells
FIG 2.19 Transverse section of a wheat grain showing the
tissues of the crease region. Modified from A. L. and K. B.
Winton (1932).
Outside the nucellar projection (as the column
is called) there is a discontinuity in the testa, in
which lies a bundle of corky cells forming the
pigment strand. Its name is derived from the dark
colour which it exhibits in red wheats. It is not
highly pigmented in white wheats. Between the
nucellar projection and the endosperm lies a void
known as the endosperm cavity.
Wheat aleurone tissue is but one cell thick, the
cells being approximately cubic with 50 pm sides.
Some remnants of the mesocarp remain as inter-
mediate cells. The disintegration of most of the
mesocarp leaves a space between cross cells and
outer epidermis, which is thus only loosely attached
except in the crease where the mesocarp persists.
The tube cells are separated by many large gaps
except where they cover the tips of the grain.
The cellular nature of the tissues is shown in
Fig. 2.20 (although an old publication The Stucture
and Composition of Foods by Winton and Winton
(1932), from which this illustration is taken, pro-
42 TECHNOLOGY OF CEREALS
FIG 2.20 Bran tissues of wheat in surface view. 1-6 are pericarp components. 1. Fragment of epidermis
with brush hairs; 2. epidermis on body of grain; 3. hypodermis; 4. intermediate cells; 5. cross cells,
6. tube cells; 7. outer and inner testa layers; 8. nucellar epidermis. 9. aleurone cells. Modified from
A. L. and K. B. Winton (1932).
to anthocyanidin pigmentation. In the starchy
endosperm two populations of starch granules are
present in most types, though in some mutants,
exploited for their chemically different starch,
only one population may be present.
Oats
The oat grain is characterized by pales that are
not removed during threshing. As they do not
adhere to the groat (the name describing the
actual caryopsis of the oat) within, they can be
removed mechanica11y* Oats are traded with the
husk b~ place. In this condition they have an
extremely elongated appearance and even with
the husk removed groats are long and narrow.
Within a spikelet the two grains present differ in
form, the lower being convex on the contact face
while the upper grain has a concave face (Fig.
2.21).
The groat’s contribution to the entire grain
mass varies from 65 to 81% in cleaned British-
grown oats (average 75%). Differences are due to
Lemma
& Palea
w Lemma
FIG 2.21 Diagrammatic transverse section through an oat
spikelet showing the relationship between the grains within,
accounting for their different shapes.
both variety and environment. The groat contri-
bution tends to be higher in winter-sown than in
spring-sown types, in Scottish-grown than in
English-grown samples, and in small, third grains
than in the large, first (main) grains of varieties
with three grains per spikelet (Hutchinson et al.,
1952).
BOTANICAL ASPECTS OF CEREALS 43
FIG 2.23 Transverse section through a rice grain showing the
‘locking’ mechanism of the lemma and palea. Modified from
A. L- and K. B. Winton (1932)-
together by a ‘rib and groove’ mechanism (Fig.
2.23).
FIG 2.22 Bran coats of oat in surface view. 1. Outer epidermis;
2. hyperdermis; 3. testa; 4. aleurone. Modified from A. L.
and K. B. Winton (1932).
Naked Oats Avena nuda L* is a type Of Oat which
readi1y loses its husk during threshing, thus
Once the pales are removed, the Outer epi-
dermis of the pericarp is revealed as the Outer
obviating any need for a special dehulling stage
contents, and a high energy value.
Only two pericarp layers can be distinguished
in oats, an epidermis with many trichomes on the
outer surface (unlike the Triticeae fruits, these
are not restricted to the non-embryo end) and a
hypodermis, consisting of an irregular, branching
collection of worm-like cells with long axes lying
in all directions (Fig. 2.22).
The testa comprises a single cellular layer with
cuticle. In cross section the nucellar epidermis
can be seen as a thin colourless membrane, its
cellular structure cannot be discerned, and a
cuticle separates it from the testa.
In the endosperm there is a single aleurone
layer. The cell walls are not thick, as they are in
wheat and rye. Conversely, the starchy endo-
sperm cells have thicker walls than in wheat.
Starch granules are polydelphous (compound)
consisting of many tiny granufi which fit together
to form a spherical structure. Possibly eighty or
more granuli up to 10 pm diameter constitute a
single compound granule- Individual free granuli
are also Present in the spaces among the agflegates-
Endosperm cells of the oat have a relatively high
oil content.
Rice
grain only with difficulty, as they are locked
layer of the caryopsis. Unlike the other small
have a crease. It is laterally compressed and
the surface is longitudinally indented where
broader ribbed regions of the pales restricted
expansion during development. Distinctively, in
all except one of the tissue layers (the tube
cells) surrounding the endosperm, the cells are
elongated transversely (in other grains only the
cross cells are elongated in this direction). Cells
Of the ePidermis have waV wal1s making them
quite distinct from those of the hypodermis, with
their flat Profiled walls- Cross cells have many
intercellular spaces and the cells are worm-like;
similar to, but lying at right angles to, the tube
cells. The testa has one cellular layer, with an
external cuticle. Cells of the nucellar epidermis
are similar to those of the testa but the walls
have a beaded appearance in section. Aleurone
cells are similar to those of oats, but the number
of layers varies around the grain from one to
three.
Starch granules in the starchy endosperm cells
are similar to those of oats. Unusually, the
embryo of rice is not firmly attached to the
endosperm.
The proportion of husk in the rice grain
averages about 20%. Varieties of rice are class-
The pales of rice are removed from the ified according to grain weight, length and shape
-which is described as round, medium or long,
in mi1ling* Naked Oats have high protein and Oil
grained cereals described above, rice does not
44 TECHNOLOGY OF CEREALS
and defined by their aspect ratio (length to
breadth). In shape, grains of the indica type are
section; grains of japonica rice are long, narrow
and slightly flattened in shape.
Maize (Dent corn)
Although there are many types of maize and
their morphology and anatomy vary (Watson
1987), it is possible only to describe one type
here; dent corn is the moSt abundant1y grown FIG 2.24 Section through a sorghum grain. Modified from
and this explains its selection. The maize grain A. L. and K. B. Winton (1932).
is the largest of cereal grains. The basal part
Sorghum
(embryo end) is narrow, the apex broad. The
embryonic axis and scutellum are relatively large.
The pericarp is thicker and more robust than The following description applies essentially to
that of the smaller grains. It is known as the hull the type of grain sorghum which is grown in the
and the part of the hull overlying the embryo is U.S.A. but variations found in other types are
known as the tip-cap. An epidermis is present as also noted. Grains are near-spherical with a
the outermost layer, no hairs are present. Beneath relatively large embryo. A single outer epidermis
the epidermis lie up to 12 layers of hypodermis, of the pericarp surrounds the grain. Within
which appear increasingly compressed towards it are two or three hypodermis layers. The
the inside. Both tube cells and cross cells are mesocarp is one of two unusual features of the
present, cross cells occuring in at least two layers. sorghum grain; it consists of parenchymatous
Cell outlines are extremely irregular and there are cells that still contain starch at maturity. The
many spaces among the anastomosing cells. No cells are not crushed as in other cereals (Fig.
cellular testa layer is present but a cuticular skin 2.24).
persists to maturity. The same applies to the The starch granules are up to 6 pm diameter;
nucellus. smaller than those in the endosperm. Cross cells
In spite of the great size of the endosperm of do not form a complete layer, they are elongated
maize, individual aleurone cells are small, compar- vermiform cells aligned in parallel but separated
able to those of oats and rice. One layer of them by large spaces. Tube cells on the other hand are
is present. In blue varieties it is the aleurone cells numerous and closer packed. The second unusual
that provide the colouration. In the starchy feature of sorghum anatomy is the absence of
endosperm many small starch granules (average the testa. The nucellar layer is, however, well
10 pm) occur. Protein (zein) also occurs in tiny developed; in fact it is the most conspicuous of
granular form. Horny endosperm occurs as a deep all the bran layers and may be up to 50 pm thick
cap surrounding a central core of floury endosperm. and coloured yellow or brown. There are different
The designation ‘dent’ results from the indenta- opinions among authors as to the identity of the
tion in the distal end of the grain which contracts seed coat layers. Some refer to a testa rather than
on drying. The dent is not found in other types a nucellar epidermis. There is general agreement
of maize such as flint maize, popcorn, and sweet- that it may be clear or coloured and also that it
corn. The most significant differences among may be incomplete.
maize types lie in the endosperm character and Aleurone cells are similar in size and appearance
shape. The covering layers are similar but other to those of maize as are the inner endosperm
types may have fewer hypodermis layers than cells and the starch granules that they contain.
dent corn. Peripheral endosperm cells however are less
short, broad and thick, with a round cross-
pericarp
nucellar epidermis
endosperm
BOTANICAL ASPECTS OF CEREALS 45
such confusion and, indeed, in practice it un-
doubtedly clarifies communications. However,
experts are not agreed on all details and several
systems of scientific nomenclature exist. Attempts
have been made to reach a concensus and the Inter-
national Standards Organization has published a
list of the agreed names. These are given in Table
2.3 which, in addition to systematic and common
names, includes the number of chromosomes
typical of each species.
clearly distinguished from the aleurone cells to
which they are adjacent.
In some sorghums pigmentation occurs; all
tissues may be coloured, but not all together.
The starchy endosperm may be colourless or
yellow, the aleurone may or may not contain
pigmentation. The pericarp and nucellar layers
may contain variable amounts of tannins: poly-
phenolic compounds responsible for red coloura-
tion. Types with large proportions of tannins in
the pericarp are known as ‘bird proof’ or ‘bird
repellant’ because, it is assumed, of the unpalat-
ability of the polyphenols. They are certainly
attacked less by birds than are white types (cf. The primary objective of plant classification is
Ch. 4). the grouping of plants and populations into
An African sorghum ‘kaffir corn’ does not have recognizable units with reasonably well defined
the usual conspicuous nucellus described above. boundaries and stable names. Modern taxonomists
The hypodermis is more robust due to thicker strive to establish a phylogenetic arrangement of
cell walls. Both white and red varieties are the taxa, based on known or presumed genetic
cultivated. Further information may be found in relationships.
Hulse et al. (1980), Winton and Winton (1932) Living organisms are classified in a hierarchical
and Hoseney and Variano-Marston (1980). system in which descending groupings indicate
progressively closer relationships. The lowest
taxonomic level to which all cereals belong is
the Family. A Family may be divided into
The Millets
Not all types can be described here as there sub-families, each of which is further divided
are many and not all are well documented (Hulse into tribes. Within a tribe there may be several
et al., 1980). Some details are given of the most genera and there may be several species within a
widely grown: pearl millet. genus. The species is the highest level at which
The grain is about one third the size of sorghum routine natural breeding among members would
grain, the epidermis/hypodermis combination be expected.
being thicker than that of sorghum; cross cells Within a species there may be several cultivars,
and tube cells are spongy. No cellular seed coat which, if accepted by an appropriate authority,
is present but a membranous cuticle is. A single may be recognized as commercial varieties. At
layer of aleurone cells surrounds a starchy endo- the species level binomial designation applies, the
sperm with horny and floury regions. The aleurone first part of the name being that of the genus, for
cells have conspicuous knobbly thickening. Similar example ‘Hordeum’. Addition of the trivial name
cells have been noted in foxtail millet and assigned ‘vulgare’ completes the specific name: Hordeum
a transfer function. vulgare. (In the case of barley the two-rowed and
four-rowed types are distinguished at the ‘convar’
level - this lies between species and cultivar in the
taxonomic hierarchy.) It is customary to print speci-
fic names in italics or to underline them. Designa-
tion of taxonomic status is somewhat arbitrary.
Those competent taxonomists responsible for
establishment of species are credited by their
name being suffixed to the species name, either
in full or in shortened form. The most frequent
Classification
Tax0 n o m y
The names commonly applied to individual
species are sometimes confusing as many different
names may be used for the same plant. Worse
still, the same name may be applied to more than
one plant or its fruit. Theoretically the application
of systematic nomenclature should remove all
46 TECHNOLOGY OF CEREALS
TABLE 2.3
Taxonomic Details of Cereals
Cereal type Systematic name (Chromosomes) Common name
Wheat Triticum aestivum L. emend Fiori et Paol wheat, breadwheat
(2n = 42)
(2n = 42)
(2n = 28)
(2n = 28)
(2n = 14)
(2n = 28)
(2n = 42)
(2n = 42)
(2n = 28) wheat
Triticale Triticosecale ssp Whitmark triticale (hexaploid or octaploid)
(2n = 42 or 56)
(2n = 14)
(2n = 14)
(2n = 14)
(2n = 14)
(2n = 42)
Avena byzantina Karl Koch
(2n = 42)
Avena nuda L.
(2n = 42)
(2n = 24)
(2n = 24)
(2n = 20)
(2n = 20)
(2n = 20)
(2n = 20)
(2n = 20)
(2n = 20)
(2n = 20)
(2n = 20)
Triticum aestivum ssp compacturn Hosteanum
Triticum dicoccum Schrank emmer wheat
Triticum durum Desfontaines durum wheat
Triticum nwnococcum L.
Triticum polonicum
Triticum spelta L.
Triticum sphaerococcum Percival
Triticum turgidum L.
club wheat
small spelt, einkorn
diamond wheat, Polish wheat
spelt wheat, dinkel
shot wheat, Indian dwarf wheat
English wheat, rivet wheat, poulard
Rye Secale cereale L. rye
Barley Hordeum vulgare L. sensu0 lato barley
Hordeum vulgare convar distichon
Hordeum vulgare convar hexastichon
two-rowed barley
six-rowed barley
Oats Avena sativa L. common oats, white oats
Algerian oats, red oats
naked oats, hull-less oats
Rice Oyza sativa L. rice
Oyza rujipogon (Griffiths)* red rice
Maize Zea mays L. maize, corn
Zea mays convar amylacea
Zea mays convar ceratina
Zea mays convar everta popcorn
Zea mays convar indentata
Zea mays convar indurata
Zea mays convar saccharata
Zea mays convar tunicata
soft maize, flour maize
waxy maize
dent maize
flint maize
sweet corn, sugar maize
pod maize
* May be classed as a millet.
BOTANICAL ASPECTS OF CEREALS 47
TABLE 2.3
Continued
Cereal type Systematic name (Chromosomes) Common name
Sorghum Sorghum bicolor (L.) Moench sorghum, guinea-corn, great millet,
Egyptian millet, kaffir corn, dari,
milo, waxy milo, jowar, cholain,
milo-maize, kaoliang, feteritas,
shallu, broomcorn
(2n = 20)
Millets Brachiaria deflexa (Schumacher) Hubert fonio
(alphabetical)
Coix lanyma-jobi L.
Digitaria exdis (Kippist) Stapf.
Digitaria iburua Stapf. black fonio
Echinochloa crus-galli (L.) P. Beauvoir
adlay, Job’s tears
acha, fonio, hungry rice
(2n = 20)
(2n = 54)
(2n = 54)
var fimentacea (Roxburgh)
(2n = 36 or 54) W. F. Wight cockspur grass
Eleusine coracana (L.) Gaertner
(2n = 36)
Eragrostis tef (Zuccagni) Trotter
(2n = 40)
Panicum miliaceum L.
(2n = 36 or 72)
Japanese millet, barnyard m., Billion
dollar grass, white panicum,
finger m., ragi, Indian m., birdsfoot
teff, teffgrass
common m., Australian white m.,
m., African m., marica
Chinese red m., hog m., Moroccan
yellow m., plate m., proso (cheena)
m., Turkish yellow m., U.S.A.
proso m. (cheena), U.S.A. red m.,
corn m., samai, broomcorn
Panicum miliare Lamarck little m.
Paspalum scorbiculatum L.
Pennisetum glaucum (L.) R. Brown
(2n = 36)
kodo m., ditch m., kodra, kodon,
varagu, scrobic
pearl m., inyati m., babala seed,
bulrush m., cattail, pale rajeen
grass, bajra, African m., candle
m., cumbu
foxtail m., German m., Australian
m., Chinese yellow m., seed of
Anjou sprays, seed of Burgundy
sprays, seed of Italian sprays,
Hungarian m., Italian m.
(2n = 14)
Setaria italica (L.) P. Bauvois
name suffured is Linnaeus or L., crediting the
Swedish biologist who devized the system.
Several classifications of the Gramineae family
exist. One is shown in Table 2.3. In Fig. 2.25 a
suggested family-tree is shown. The diagram
also indicates the photosynthetic pathway adopted
by members of some of the groupings. The C3
is typical of temperate plants, and the C4 is
appropriate to tropical plants.
Breeding
The process of fertilization described earlier in
this chapter is typical of outbreeding species.
Some of the most important species of cereal do
not conform to this pattern however. Although
other mechanisms may also be involved, one
certain barrier to cross-pollination is the failure of
anthers to emerge from the pales before shedding
Gramineae
- Arundinaideae
- Bambusoideae
Chlarideae (C4) Eteusine
_I Eragrosteae (C4)
- Chloridoideae
- Oryzoideae (C3) Oryzeae Oryza
Brachoria
Digi toria
Echmoch(oo
Panicum
Paspa(um
Pennise tum
+ Setaria
-4 Andopoganeae (C4) -E :!hum
Paniceae (C3 and C4)
Avena
Hordeum
- Panicaideae
- Poideae (C4)
BOTANICAL ASPECTS OF CEREALS 49
FIG 2.26 Reduction in vigour in maize with successive generations of inbreeding. So represents the
original inbred plant and S14 successive inbred generations. Reproduced from Poehlman (1987), by
courtesy of Avi Publications, New York.
Hybridization its parents, this being referred to as the mid-
parent value. In practice, hybrid vigour is the
The crossing to produce heterozygosity and
increase in size and vigour over the better parent
selection of a pure line from an advanced line
as this is the only achievement of interest to
following the cross is known as hybridization. It
growers or processors~
When growing hybrid maize, the farmer gener-
should not be confused with the breeding of
ally obtains fresh hybrid seed each year from
hybrids in which the F1 generation is grown
commercially. The FZ generation is the first filial
growers who specialize in its production. The
generation or that produced immediately from
specialized grower chooses an isolated field on
the cross. This method is used most effectively
which he grows two inbred lines of maize in
with species such as maize and sorghum which
naturally outcross. The simplest method of pro-
to about four rows of female parent plants. At the
duction is to grow the F1 of a cross beween inbred
appropriate time, the femde plmts are detasselled,
frequent1y used. These inc1ude modified sing1e adjacent male parent plants. Seed is later collected
crosses, backcrosses, synthetic varieties and com- method of producing hybrid maize is by use of
posites. Explanations of these terms can be found male sterility, which may be genetic or cytoplasmic.
in specialized texts such as that of Poehlman Before 1970, over 90% of maize seed in the
(1987). Whereas conth~d inbreeding of Out- U. S.A. produced in Texas utilized male-sterile
breeding species leads to loss of vigour, F1 cytoplasm, but after 1970, when the fungus
hybrids produced from inbred lines exhibit Helminthosporium may& race T caused much
heterosis, or hybrid vigour. This is the increase damage, cytoplasmic male-sterility was not used
in size or vigour of a hybrid over the average of for a few years. It subsequently made a return
alternate strips, one row of male parent plants
lines, but more “Phisticated techniques are now
and are subsequently fertilized by pollen from the
or three-way crosses, double crosses, multiple
from the female parent only. An alternative
50 TECHNOLOGY OF CEREALS
but the detasselling method is most frequently An example of an allopolyploid produced by
used. design is triticale (Triticosecale), a hybrid of wheat
As both male and female reproductive parts and rye which contains complete genomes of both
occur in the same spikelets of sorghum, produc- parents. Triticales have been produced indepen-
tion of hybrid sorghum seed awaited development dently with several wheat parents (rye is always the
of male-sterile types. Hybrid sorghum was first pollen parent). Both hexaploid triticales, produced
grown commercially in 1956. F1 hybrids are from a tetraploid wheat and diploid rye, and octo-
commercially successful in millets also. ploid triticales, with a hexaploid wheat parent,
Attempts have been made to produce F1 hybrids have been produced. The philosophy behind
from inbreeding cereals and this has been achieved, triticale breeding has been the combination of the
but not yet commercially, in wheat, oats and hardiness of rye with the grain quality of wheat
barley. In China there are reports of successful (cf. Ch. 4.) The most successful triticales have been
commercial rice F1 hybrids (Poehlman 1987). secondary triticales, those resulting from a cross
between primary triticale (rye x wheat) and wheat.
Other cereal intergeneric hybrids have been bred
experimentally but none has reached commercial
Intergeneric hybrids
Genes capable of coding for all plant characters scale production. The future of triticale as a
are accommodated on a relatively small number widely grown commercial cereal remains uncertain.
of chromosomes. In wheat the minimum number
Breeding objectives
is 7. Somatic (non-reproductive) cells are diploid,
that is, they contain two sets of chromosomes;
they thus have two genes for each character. One To the grower the most important characters
gene of each pair may be dominant and it is this of a cultivar may be related to the responses of
that is expressed. Other degrees of co-operation the whole plant to environmental pressures, while
are also possible. In some plants there are two or to the processor: the miller, the maltster or the
three or even four pairs of chromosomes per cell starch manufacturer it is the grain characteristics
instead of the usual one pair. Those with only that are most important. Poehlman (1987) lists
one pair are termed euploid, while those with objectives for a number of cereals, acknowledging
more are polyploid. Polyploid plants may arise that the emphasis may vary from one part of the
as a result of duplication of the inherent chromo- world to another.
somes to form autopolyploids, or by combining The primary objectives for all species are yield
chromosome complements (genomes) from two potential, yield stability (including: optimum
or more species, leading to allopolyploids. Poly- maturity date, resistance to lodging and shatter-
ploids of both types can occur in nature or they ing, tolerance to drought and soil stress, and
can be induced by breeders. They are larger than resistance to disease and pests) and grain quality.
either parent and generally exhibit greater vigour The factors involved in yield stability are to some
also. An example of a natural allopolyploid is bread extent linked, for example resistance to lodging
wheat, Triticum aestivum. It is hexaploid, with six (the tendency of standing crops to bend at or near
of each type of chromosome in each somatic cell. ground level, thus collapsing) might involve the
The three different genomes (each of 2 x 7 chromo- height of the plant, the size and weight of the ear
somes) came from three different species of grass, in relation to culm strength and resistance to stem
none of which had all the characteristics of rot pathogens and to insects such as the corn borer.
the resulting species. Other wheats have fewer In some cereals additional objectives include
genomes, for example T. durum is tetraploid and the production of hull-less varieties of oats and
T. monococcum is diploid. Oats and some millets barley and the adaptation to mechanized harvest-
are further examples of natural allopolyploid ing of sorghum and millets. In barley, low yield
(hexaploid) species grown commercially. For the remains a problem and varieties with smooth
ploidy of other cereals see Table 2.3. awns are also desirable. Some winter-sown cereals
BOTANICAL ASPECTS OF CEREALS 51
such as wheat, oats and barley provide herbage HOSENEY, R. C. and VARIANO-MARSTON, E. (1980) Pearl
for stock grazing on vegetative parts of immature millet: its chemistry and utilization. In: Cereals for Food
and Beverages, INGLETT, G. E. and MUNCK, L. (Eds.)
plants in the autumn, and good fodder properties Academic press I~~, NY. U.S.A.
may thus be desirable. Fodder aspects also feature HOSHIKAWA, K. (1967) Studies on the development of rice
in breeding programmes for millets and sorghum. 2. Process of endosperm tissue formation with special
reference to the enlargement of cells, and 3. Observations on
Aflonomic characters Of hpoflance to breeding the cell division. Proc. Crop Sci. SOC. Japan. 36: 203-216.
programmes include the seasonal habit. Winter- HUBBARD, C. E. (1954) Grasses. Penguin Books Ltd.
sown crops of a given cereal produce greater Harmondsworth~ Middx.
HULSE, J. H., LAING, E. M. and PEARSON, 0. E. (1980)
yields than those Sown in Spring. SPring-sown
Sorghum and the Millets: Their Composition and Nutritive
types need to grow rapidly in order to complete Value. Academic Press Inc. London.
the necessary phases of growth in a relatively HUTCHINSON, J. B., KENT, N. L. and MARTIN, H. F. (1952)
The kernel content of 0ats.J. mtn. Inst. agric. Bot. 6: 149.
short period* They must not require a period Of I.S.0.5526 (1986) Cereals, pulses and other food grains -
cold treatment known as stratification when it Nomenclature. International Standards Organization.
promotes germination or vernalization when it is (Dua1 numbered as B.S.l. 6860 1987).
JULIANO, B. 0. and BECHTEL, D. B. (1985) The rice grain
necessary to promote production of reproductive and its gross compsition. In: Rice: Chemistry and Technology,
structures in the first flowering season (some JULIANO, B. 0. (Ed.) Amer. Assoc. of Cereal Chemists
Inc. St Paul MN. U.S.A.
cerea1s are natura11y perennia1s a1though they KENT, N. L. (1966) Subaleurone endosperm of high protein
are treated as annuals in agriculture). A more content. Cereal Chem., 43: 585.
ambitious objective may be the breeding of crops KENT, N. L. (1966) Technology of Cereals, 1st edn, Pergamon
with special qualities previously not associated Press Ltd, Oxford.
KENT, N. L. (1983) Technology of Cereals, 3rd edn, Pergamon
with the species concerned. An example of the Press Ltd, Oxford.
successful achievement of this objective is the KIESSELBACH, T. A. (1980) The Structure and Reproduction of
Corn. University of Nebraska Press. (Reprint of 1949 edn).
breeding Of maize with high amy1ose Or high LANDES, A. and PORTER, J. R. (1989) Comparison of scales
amy1opectin starch, Or high lysine maize. Breeding used for categorizing the development of wheat, barley,
objectives related to processing are discussed for rye and oats. Ann. appl. Bot. 115: 343-360.
NICHOLSON, B. E., HARRISON, S. G. MASEFIELD, G. B. and
WALLACE, M. (1969) The Oxford Book of Food Plants.
individual cereals in Ch. 4.
Oxford University Press.
PALMER, G. H. (1989) Cereals in malting and brewing. Ch. 3.
References
In: Cereal Science and Technology, PALMER, G. H. (Ed.)
pp. 61-242, Aberdeen University Press, Aberdeen.
BENNET~ D. M. and PARRY, D. w. (1981) E1ectron-probe PERCIVAL, J. (1921) The Wheat Plant. Duckworth and Co.
microanalysis studies of silicon in the epicarp hairs of the London. Reprinted 1975.
caryopses of Hordeum sativum Jess, Avena sativa L., &de
PETERSON, R. F. (1965) Wheat: Botany, Cultivation and
cereale L. and Triticum aestivum L. Ann. Bot. 48: 645-654. Utilization. Leonard Hill Books, London.
BREMNER, p. M. and RAWSON, H. M. (1978) The weights POEHLMAN, J. M. (1987) Breeding Field Crops. 3rd edn. AVI
of individual grains of the wheat ear in relation to their Publishing Co. Ltd Westport, Connecticut. U.S.A.
growth potential, the supply of assimilate and interaction RADLEY, M. (1976) The development of wheat grains in
between grains. Aust. J. Plant Physiol. 5: 61-72. relation to endogenous growth substances.J. exp. Bot. 27:
BRIGGS, D. E. (1978) Barley. Chapman and Hall, London. 1009-1021.
BRIGS, D. E. and MACDONALD, J. (1978) Patterns of REXEN, F. and MUNCK, L. (1984) Cereal Crops for Industrial use
modification in malting bar1ey.J. Inst. Brew. 89: 260-273. in Europe. The Commission of the European Communities.
BUSHUK, W. (1976) Rye, Production, Chistry and Technology. ROST, T. C. and LERSTEN, N. R. (1970) Transfer aleurone
Amer. Assoc. of Cereal Chemists Inc. St Paul MN. U.S.A. cells in Setaria lutescans (Gramineae) Protoplasma. 71:
ENNOS, A. R. (1991) The mechanics of anchorage in wheat 403408.
Triticum aestivum L. 2. Anchorage of mature wheat against SWIFT, J. G. and O'BRIEN, T. P. (1970) Vascularization of
lodging. J. exp. Bot. 42: 1607-1613. the scutellum of wheat. Aust. J. Bot. 18: 45-53.
EVERS, A. D. and BECHTEL, D. B. (1988) Microscopic WANOUS, M. K. (1990) Origin, taxonomy and ploidy of the
structure of the wheat grain. In: Wheat: Chemistry and millets and minor cereals. Plant Varieties and Seeds. 3:
Technology, POMERANZ, Y. (Ed.) Amer. Assoc. of Cereal 99-112.
Chemists Inc, St. Paul MN. U.S.A. WATSON, S. A. (1987) Structure and composition. In: Corn:
FULCHER, R. G. (1986) Morphological and chemical organ- Chemistry and Technology, WATSON, S. A. and RAMSTAT,
ization of the oat kernel. In: Oats: Chisny and Technobgy, P. E. (Eds). Amer. Assoc. of Cereal Chemists Inc, St.
WEBSTER, F. H. (Ed.) Amer. Assoc. of Cereal Chemists Paul, MN. U.S.A.
Inc. St Paul MN. U.S.A. WINTON, A. L. and WINTON, K. B. (1932) The Structure
GOULD, F. W. and SHAW, R. B. (1983) Grass Systematics. and Composition of Foods. Vol. I. Cereals, Starch, Oil seeds,
Texas A and M University Press. Nuts, Oils, Forage Plants. Chapman and Hall. London.
52 TECHNOLOGY OF CEREALS
ZADOKS, J. C., CHANG, T. T. and KONZAAK, C. F. (1974) BEWLEY, J. D. and BLACK, M. (1982) Physiology and
A decimal code for the growth stages of cereals. Weed Res. Biochemistry of Seeds in relation to Germination. Vol. 2.
14: 415421. Viability, Dormancy and Environmental Control. Springer-
ontogeny of the pigment strand in the caryopsis of wheat. BLAKENEY, A. B. (1992) Developing rice varieties
Aust. J. Bot. 23: 107-110. with different textures and tastes. Chemy Aust. Sept.
475476.
BUSHUK, W. and LARTER, E. N. (1986) Triticale: production,
chemistry and technology.Adv. CerealSci. Tech. 8: 115-158.
MAUSETH, J. D. (1988) Plant Anatomy. Benjamin/Cummings
Publ. Co. Inc. Menlo Park, CA. U.S.A.
POMERANZ, Y. (Ed.) (1989) Wheat is Unique. Amer. Assoc.
RINGLUND, K., MOSLETH, E. and MARES, D. J. (Eds.) Fifth
Internatirmal Symposium on Pre-Harvest Sprouting in Cereals.
Westview Press, Boulder, Colorado. U.S.A.
ZEE, S.-Y. and O’BRIEN, T. P. (1970) Studies on the Verlag. Berlin.
Further Reading
ANON. (1989) Biological Nomenclature. Institute of Biology,
BEWLEY, J. D. and BLACK, M. (1978) Physiology and of Cereal Chemists Inc. St. Paul MN. U.S.A.
London.
Biochemistry of Seeds in relation to Germination. Vol. 1.
Development, Germination and Growth. Springer-Verlag.
Berlin.
