|Plants & Human Affairs (BIOL106) - Stephen G. Saupe, Ph.D.; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; email@example.com; http://www.employees.csbsju.edu/ssaupe|
Cereals - the Staffs of Life
maize, wheat - top three main crops worldwide
are among the first cultivated crops (barley, wheat, maize)
- important part of most cultures
culture, with the exception of high Andes, developed a cereal
food source for approx. 2 billion people
for Ceres - Goddess of crops
Why are cereals so important?
They are important because:
resist spoilage (i.e., low moisture);
highly caloric (provide at least one half of the worlds calories);
seeds in a cluster making them easy to harvest;
easily grown, most are self compatible
III. What is a cereal?
Member of the grass family (Poaceae, also called Graminae)
Grasses can be annual or perennial.
The roots of grasses are fibrous, which makes them good soil binders and the reason they are planted for erosion control.
Grass stems are called culms. These are usually hollow, except at the nodes. Branches that originate from near ground level are tillers. Many grasses have a rhizome, stolon, etc.
Typically alternate and in one plane. The leaf is made of three parts; blade, sheath and ligule. The sheath is usually not fused around the stem, but rather is open. The ligule is a small tissue found between the blade and sheath. It can be hairy, membranous, even absent, and is important taxonomically. There may also be auricles present, which are small ear‑like appendages at the junction of sheath and blade.
Perfect and imperfect (plants usually monoecious, rarely dioecious). The petals and sepals are absent, reduced to lodicules. There are 2 - 3 lodicules per flower. The function of the lodicules is to open up the flower (they absorb water and swell pushing apart the bracts surrounding the flower).
Usually three stamens, these typically dangle out of the flower at maturity.
The pistil has 2, feathery styles.
Grasses are adapted for wind pollination. Adaptations for wind pollination: copious amounts of pollen, plumose stigmas, anthers stick out of the flower when the flower is mature.
Caryopsis or grain, single seeded fruit in which fruit wall and seed
coat are fused and indistinguishable from one another.
Parts of the grain: embryo (germ) - rich in oil/protein; endosperm - rich in starch; aleurone layer - protein/oil, secretes enzymes to initiate germination; bran - fruit and seed walls. Polished grain - removed bran and aleurone. One advantage is that the grain will not spoil as readily; the disadvantage is that it removes much of the nutrional value of the grain.
The flowers are subtended by modified leaves called bracts. The outer bract (lemma) may form an extension called an awn. The palea is the inner bract. It is generally smaller, oriented toward the main stem axis, and 2 veined. A flower with lemma and palea is a floret.
Florets are arranged in clusters called spikelets. The bottom pair of bracts of a spikelet are sterile (no flower in axil) and are called glumes. A spikelet may be comprised of from one to many florets. The inflorescence is considered to be an arrangement of spikelets rather than individual flowers.
Plants that bear a superficial resemblance to the true grasses and/or have seeds that do and are used in similar ways as cereal grains. Examples are Amaranth, quinoa (Chenopodium quinoa) and buckwheat (Fagopyrum esculentum)
V. Domestication/Selection of cereals
The following is a series of trends in the domestication of cereals (these were also discussed in our Origin of Agriculture class)
Dwarf plants - minimize lodging
Unbranched - more grains per stalk and more synchronous ripening
Synchronization of ripening
Synchrony of tiller formation - ease of harvest, maximize yield
Fruit retention - eliminate shattering
Ease of threshing and winnowing - threshing is the process of separating the grain from the bracts (chaff); winnowing is the process of removing freed grain from the chaff. Traditional methods vs. modern.
grain size and quality
Maize (Zea mays)
Commonly called corn in N. America. However, corn is a generic name for any cereal in some parts of the world (i.e., Britain).
Tassel (male flowers) , silks (styles, female flowers), monoecious, imperfect flowers, ear - lateral shoot, short internodes, subtended by up to seven leaves (husks).
of maize - based upon the type and distribution of starch in the grain, and
the shape of the kernel (which is related to starch content).
Countless. Food, silage, fermented into beverages (beer, bourbon) and gasoline additives, corn syrup, cellulose for rayon
Where did maize come from and how did it evolve?
1. Mexico - approx 6000 BC
Recent studies by John Doebley and colleagues, Hugh Iltis, and others have shown that corn and teosinte differ by about five different genes. This is fewer than originally anticipated and suggests why corn rapidly appears in the archaeological record.
Wheat (Triticum sp.)
Evidence for wheat as early as 8-7,000 BC; domesticated in Near East
Einkorn (Triticum monococcum).
This was the first cultivated wheat. Wild forms (they shatter) are known). It has 14 chromosomes (2n = 14).
Emmer (Triticum turgidum).
This is a hybrid between einkorn and a wild wheat and resulted from a doubling of the chromosomes. It has 28 chromosomes (4n).
Durum (Triticum durum).
Probably a mutation that was derived from emmer wheat. The main differences between emmer and durum is that durum wheat is: (a) free threshing; and (b) good quality protein (gluten). Makes semolina flour that is used extensively in pastas. Grown in northern US especially ND and Canada. Has 28 chromosomes (tetraploid).
Bread (Hard/Soft, Red or Club; Triticum aestivum).
This is the major wheat in cultivation. It has a high protein content and good gluten. It has 42 chromosomes - is a hexaploid and is a result of a cross with Aegilops squarrosa.
The success of the wheat crop in the US was dependent on:
VIII. Rice (Oryza sativa)
- sacred symbol of fertility in the Orient; extremely important crop,
perhaps one of most important; domesticated in Asia (Thailand/Burma) around
7000 BC. Feeds more people than any other cereal.
are two sub-species of rice:
1. Oryza sativa var. indica - Long grain. This is dry, separates on cooking. Grown in tropical and subtropical areas. The amylopectin content is greater than the amylose content.
2. Oryza sativa var. sativa - Japonica or short grain rice. Soft and gluey texture because of amylopectins and dextrose. More temperate.
Rice requires much water. Upland rice - wet but not standing water; Paddy rice - prefers standing water. Most of the world's rice is grown in paddies. Air chambers in the stem help to move oxygen (air) to the roots that are embedded in the rather anaerobic (oxygen-free) soils. An aquatic (floating) fern (Azolla) is often cultivated with rice as a type of green manure. Azolla is able to fix nitrogen and act as a natural fertilizer for the rice. Traditionally, seedlings are individually planted in the paddies. In the US, rice is usually seeded directly in the field, sometimes by airplane.
White rice - remove bran and seed coat. Polished rice - removes bran, seed coat embryo and aleurone layer. Obviously removes most of the nutrients. Beri-beri - deficiency of vitamin B1 (source of thiamine).
Rye (Secale cereale)
to SW Asia.
a seed in barley fields = secondary crop
about 3000 BC
hardy - cold & drought tolerant
for forage, feed, erosion control, fermented to whiskey
common host for ergot
x rye hybrid
yield and nutritionally superior
Oats (Avena sativa)
domesticated cereal (ca 1000 BC)
used as a forage crop
Barley (Hordeum vulgare)
domesticated cereal 7-10,000 ybp in Fertile Crescent (Iran, Iraq, Turkey)
row vs. 6 row
- rubbed against disks
used in pastes, toasted, porridges, breads, beers
half of crop feed to cattle, one quarter for beer making
Wild Rice (Zizania aquatica)
New World (i.e., MN)
now paddy grown
Sorghum (Sorghum bicolor)
(a) grain - food; (b) sweet or sorgho - animal feed; (c) Sudan grass;
(d) broom corn
hot regions, tolerates low rainfall
Last updated: 01/07/2005 / � Copyright by SG Saupe / URL:http://www.employees.csbsju.edu/ssaupe/index.html