Cereals
Senior 3 · Agriculture
Cereals
Lesson 1 of 4
25 min
Let's begin
Maize in a Nyagatare field can stand taller than a man; rice in a marshland in Rusizi stands knee-high in water; wheat on the slopes of Musanze grows in dense, bearded ears. They look very different, yet botanists put them in the same family, and a farmer who understands that family can grow any of them. In this lesson you will learn the features that all cereals share, how to tell them apart, and what is inside the grain you eat.
Definition
Cereal: a plant of the grass family (Poaceae, also called Gramineae) grown for its edible grain. Examples: maize, rice, sorghum, wheat, finger millet, barley, oats.
Monocotyledon: a flowering plant whose seed has only one seed-leaf (cotyledon). All cereals are monocotyledons.
Caryopsis: the one-seeded dry fruit of a grass, in which the fruit wall is fused to the seed coat. A "grain" of maize or rice is a caryopsis: botanically a fruit, not just a seed.
Inflorescence: the flowering head of a plant. Cereals carry small flowers without petals, grouped into spikelets.
Tiller: a side shoot that grows from the base of a grass plant and can carry its own head.
| Part | Cereal feature | What it means for the farmer |
|---|---|---|
| Roots | Fibrous: a mass of thin roots of similar size, with no tap root. Maize and sorghum also grow prop (brace) roots from the lowest nodes. | Roots hold topsoil well but stay shallow, so cereals need fertile topsoil and suffer in dry spells. Earthing up covers prop roots and stops lodging (falling over). |
| Stem (culm) | Jointed into nodes and internodes. Hollow in wheat and rice; filled with soft pith in maize and sorghum. | Growth happens just above each node, so a cereal can recover after hail bends it. |
| Leaves | Alternate, in two rows. Each has a sheath wrapped round the stem and a long, narrow blade with parallel veins; a small ligule sits where blade meets sheath. | Leaf colour shows nitrogen supply: pale, yellowing lower leaves signal a shortage. |
| Flowers | Small, green, without petals or scent, in spikelets. Pollinated by wind. | Varieties planted close together cross-pollinate, so seed for planting must come from a pure, certified source. |
| Fruit | A caryopsis (grain) with one cotyledon, the scutellum, and a large starch store, the endosperm. | Grain stores well when dry, which is why cereals are the basis of food security. |
| Cereal (Kinyarwanda) | Scientific name | Head | Stem | Tillers |
|---|---|---|---|---|
| Maize (ibigori) | Zea mays | tassel (male) and ear (female) | solid, pithy | few or none |
| Rice (umuceri) | Oryza sativa | panicle, drooping when ripe | hollow | many |
| Sorghum (amasaka) | Sorghum bicolor | compact or open panicle | solid, pithy, often sweet | some |
| Wheat (ingano) | Triticum aestivum | spike, often awned | hollow | many |
Soak a maize grain overnight and cut it lengthwise through the small pale patch on its flat face. You will see the parts in Figure 1.
Figure 1. Longitudinal section of a maize grain.
When a cereal germinates, the coleoptile pushes up through the soil like a spear, and the cotyledon stays in the soil (germination is hypogeal). This is why cereals can be sown a little deeper than beans.
Worked example 1: identifying a cereal from its features
Problem. A plant has fibrous roots, a hollow jointed stem, many tillers, and an unbranched head with spikelets sitting directly on the central stalk and long bristles. Name the plant and give your reasons.
Solution.
Answer: wheat, because it is the only one of the four with a spike.
Worked example 2: what a mill takes from the grain
Problem. By dry weight, a maize grain is about 82% endosperm, 11% germ, 6% pericarp and 1% tip cap. A miller who keeps only the endosperm as fine white flour mills a 50 kg bag of grain. How much flour, and how much bran and germ, does the bag give?
Solution.
Answer: 41 kg of flour and 9 kg of bran and germ, which is not waste: it is sold as animal feed. Whole-grain flour, which keeps the germ and bran, has more oil, protein, fibre and vitamins. (Percentages are typical published values, rounded.)
Warning
Common mistakes. (1) A grain is not "just a seed": the fused fruit wall makes it a fruit, a caryopsis. (2) Rice and sorghum heads are panicles, not spikes. (3) The tassel is not the maize "flower" and the cob a "fruit tree": both are inflorescences; the tassel carries the male flowers, the young ear the female flowers.
Tip
Memory hook: "Panicle branches, spike doesn't." Rice, sorghum and millet branch; wheat does not; maize splits the sexes, "tassel on top, silks below".
Ag PhD: "Farm Basics: Corn Tassels and Silks". Watch how pollen falls from the tassel onto the silks, and why every silk must be pollinated for a full cob.
Practice
Key points
Sources and credits
Written by Ganzaa: the text, the tables, Figure 1 and the worked examples. Grain composition percentages are typical rounded values.
This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.
