References:

Plants and Society, pages 188-205

On Food and Cooking, pages 230-249

The major grasses that are cultivated:

Wheat
Barley
Rye
Oats
Rice
Millet
Sorghum
Maize (corn)
Sugar Cane

The origin of wheat
The origin of rice
The origin of corn

The physical characteristics of grasses
The structure of a grass flower

Flowers of grass plants occur as parts of inflorescences. The flowers are small inconspicuous flowers that lack sepals and petals. Typically, the flowers will contain 3 stamens and one carpel. Two modified leaves called BRACTS surround each flower, and outer LEMMA and inner PALEA. The flower and two bracts make up a FLORET. One to 12 florets form a SPIKELET.

The fruits of grasses are called GRAINS. The bracts surrounding the grain are called the CHAFF. The outer wall of the fruit (caryopsis), consists of the seed coat (TESTA) fused to the pericarp (carpel wall), and this outer wall is the bran, as we have discussed earlier. Just inside the bran is the aleurone layer, which surrounds the endosperm and the embryo of the seed. The embryo is often called the GERM. When bran is separated from the rest of the seed (the endosperm and the embryo), the aleurone is usually included with the bran. The remaining endosperm and embryo is also called the germ (actually, it is only in Plants and Society that I have seen anyone call just the embryo the germ!).

The bran contains the fiber and vitamins such as B vitamins, 25% of the protein, as well as oils. Despite the added nutritional value of the bran, traditionally the milling and refining of wheat involves the removal of the bran to produce a white flour that has generally been considered a status symbol; white flour is somehow "purer" than whole grain flour. White flour is also more expensive to produce. White flour is, however, much less nutritious than whole grain flour.

However, there is some advantage to white flour. The fiber in the bran complexes with proteins, inhibiting their absorption. Wheat bran contains phytic acid, which makes calcium unavailable to the body. The nutrition section of "On Food and Cooking" points out that while fiber can aid in digestion and perhaps limit certain diseases, the diseases in question are caused by an over consumption of animal fats, and given an over consumption of animal fats, it is unlikely that fiber would be of any help. It is also interesting to note that cereal products made with refined wheat (bran removed) are fortified with B vitamins.
 

Origin of Wheat

The origin of wheat has been pretty much fully resolved by crop scientists. It is important to know the genetic background of crop plants as it allows us to breed crops to suit specific demands, at least as much as possible.

Wheat is in the genus Triticum. There are several species of Triticum, and more than one species of Triticum is ancestral to what we call wheat. Another genus of grasses, Goat Grass, genus Aegilops, is also ancestral to modern wheat.

The ancestry of wheat was determined by analyzing chromosome numbers in different grass species thought to be related to wheat. It was determined that modern wheat is the result of hybridization between different ancestral grasses, and chromosome doubling (POLYPLOIDY).

Recall that we each have 2 sets of chromosomes, one set from our mother and one set from our father. During sexual reproduction, cells called gametes are formed by the cell division called meiosis. Gametes have one set of chromosomes (gametes are haploid). During normal sexual reproduction, one gamete with say 23 chromosomes will combine with another gamete with 23 chromosomes to form a diploid (2 sets of chromosomes) cell with 46 chromosomes. That diploid cell can divide many times by mitosis to produce a sexually mature adult that can then produce gametes (with 23 sets of chromosomes).

Consider a hybridization, however, between a species (A) with 14 chromosomes and a species (B) with 28 chromosomes in each cell. Gametes of species A would have 7 chromosomes and gametes from species B would have 14 chromosomes. The diploid hybrid cell would have 21 chromosomes. This cell could divide many times by mitosis to produce a large diploid individual, but it would be sterile sexually because meiosis would be impossible. Meiosis would be impossible because at the start of meiosis, each of a pair of chromosomes are physically connected to each other (they pair up), the chromosome 1 from your father pairs with the chromosome 1 from your mother, and etc. for the rest of the chromosomes. In our hybrid plant, we have a chromosome 1 from species A and a chromosome 1 from species B, but they are different; they cannot pair up, so the hybrid is sterile. Even if the two species whose gametes combined to form the hybrid had the same number of chromosomes, they would not pair up at the beginning of meiosis, because the DNA on the chromosomes in a pair must match very well, and the chromosomes from different species do not match up well enough, and thus the hybrid would be sterile.

The basic number of chromosomes in the wheat group is n = 7, the number in gametes of plants with the smallest chromosome number. Thus the basic diploid chromosome number is 14. Einkorn wheat (Triticum monococcum) has 14 chromosomes, and is one of the first cultivated species of wheat. Einkorn wheat  hybridized with a species of Goat Grass to give rise to emmer wheat. The goat grass species has 7 chromosomes in each gamete, as does einkorn wheat, and the fusion of a gamete from einkorn wheat and a gamete from the goat grass produces a cell with 14 chromosomes, but none of the chromosomes match, so the hybrid is sterile.

In plants is is quite common for chromosomes to double (polyploidy) as the result of a simple mutation called non-disjunction. It is thought that the sterile einkorn wheat/goat grass hybrid underwent such a mutation to produce a cell with 28 chromosomes, 2 of each of the einkorn wheat and goat grass chromosomes, resulting in a plant that was not sterile; emmer wheat. Emmer wheat has 28 chromosomes, where 14 are similar to goat grass and 14 are similar to einkorn wheat. Emmer wheat was probably produced naturally, as early cultures cultivated both emmer and einkorn wheat.

The next event in the history of wheat was a sterile hybrid of emmer wheat and another goat grass, Aegilops squarrosa, which has 14 chromosomes (7 in gametes). Emmer wheat gametes each have 14 chromosomes, 7 from einkorn wheat and 7 from a goat grass. Fuse an emmer wheat gamete with an A. squarrosa gamete and you get a cell with 21 chromosomes that don't match. But get non disjunction; chromosome doubling, and you get a plant with 42 chromosomes, 2 sets of einkorn wheat chromosomes, 2 sets of the first goat grass' chromosomes and 2 sets of A. squarrosa chromosomes. The resulting plant is Triticum aestivum, bread wheat, which we like for it's high gluten content, and it has more protein as well. T aestivum appeared about 8,000 years ago.

It is my opinion that we may be under rating the abilities of early farmers in the area of genetic engineering. If they knew how to cross plant species, they could easily have produced the wheat's described above. I personally believe that they were able to make such crosses, and did do some experimentation with different plants to produce those with the desired characteristics, like high gluten content. The certainly were able to selectively breed individuals of each species where the chaff separated easily from the grain; a characteristic of cultivated wheat that is not found in wheat growing in the wild.

After learning the origins of wheat, we have been able to engineer wheat species by making specific crosses, and produce plants that can grow under specific conditions as required. We have also been able to produce very high yield plants that grow faster than their ancestors.

As we have mentioned before, refining wheat to produce the white wheat flour results in a great loss of nutrients. Wheat, among grains in general, is very nutrient rich, and removal of a good potion of the nutrients is rather foolish, especially when you consider the fact that we then "fortify" products made from white wheat flour by adding the nutrients back.

Origin of Corn

Corn is in the genus of grasses called Teosinte. Wild Teosinte species look nothing like corn. They have far fewer kernels in ear ear, and the husks of wild teosinte species shatter easily to allow for seed dispersal. Cultivated corn could not survive in the wild with the large ears producing many seeds that remain in the husk and thus cannot be dispersed.

There have been several species of teosinte proposed as ancestral to corn.  It is possible that the wild ancestors to corn are now extinct (whereas the wild ancestors of wheat are not), and thus it is difficult to determine the ancestry of corn.

Species of teosinte are described by the genus name Zea. Corn is Zea mays, as the natives to the new world called corn maize. It is likely that popcorn was more popular in early cultures because all you had to do was heat it to get it into an easily consumable food. Popcorn has a hard starch layer surrounding softer starch on the inside. The softer starch has a high water content, about 13%, and when heated, the water on the inside turns to steam, which expands and creates a pressure. When the pressure from the steam is high enough the kernel explodes, producing popped popcorn.

Popcorn is a good staple food, and has been used as such in the past. Today it is used mainly as a snack, as we all know.

Many corn species with softer endosperm have been produced, although such corn varieties are more susceptible to insect damage (it is tough for the insects to break through the hard starch layer of popcorn).
In most corn species, the endosperm contains starch. Sweet corn, however, contains sugar in the endosperm.

The color of the grain in corn has also been selected in cultivation. Grain color can result from variation in the color of the aleurone and the pericarp. In yellow corn, there is no color in the aleurone or the pericarp, and the yellow color is the color of the endosperm. In white corn, the endosperm has no color. The pericarp of indian corn can be red, orange, brown, or a mixture of these colors, while the aleurone can be red, blue purple, bronze and brown. Mixing different colors of pericarp with different colors of aleurone over the yellow endosperm can produce a variety of shades of colors, from red to green to brown to purple to even black.

Corn grows best in moderate conditions, but it does require nutrient rich soil. Corn is one of the most intensively bred plant species, and there are many varieties of corn to match a variety of environmental condition. Hybrid corn, which is sterile because chromosomes don't match up, is widely used in cultivation. Hybrid corn is produced from inbred lines of corn that are then hybridized and hybridized again. The hybrid corn grows rapidly, and is generally used by growers. Hybridization involves the removal of the tassel from the plant (emasculation) to prevent selfing, and taking the pollen from a plant with tassels and fertilizing the emasculated plant with that pollen. To better aid in hybrid corn production, female only plants have been produced (males sterile lines). These plants cannot possibly self fertilize, and thus offspring must be hybrids.

There is a price to hybrid corn. In the past, hybrid corn was produced using male sterile lines. Male sterile lines were useful, as we do not use the male part of the plant, only the female. However, a fungus appeared that attacked the male sterile lines, and caused great corn crop failures. Other male sterile lines have been developed since then.

Corn, as we have seen, is a good source of carbohydrates fats and protein, although it is low in lysine and tryptophan as well as the vitamin niacin. Corn meal, corn starch, corn oil, corn syrup and grits are well known corn products. Corn is found in many prepared foods, and is widely used in breakfast cereals and snack foods. One billion dollars worth of corn based snack foods are produced annually in the US. Corn also has industrial uses, and is used to make biodegradable plastics, ethanol based fuels, glue, and lubricants. Corn oil is naturally highly polyunsaturated, and is popular as salad oil, cooking oil, margarine and in salad dressings.

The Origin of Rice

The cultivation of rice began at about 4500 B.C. The species Oryza sativa is the main species cultivated. Rice is thought to have originated in flooded regions of the tropics. Adaptations to growing in flooded regions include air spaces in the stems that air into submerged parts of the plant, especially the roots, that will not have any other direct access to oxygen for respiration. Rice is grown almost exclusively for food, and feeds over 2 billion people in the far east, where it is the principle staple. Rice is also grown in the US, and is widely used as a food product, although the US only produces about 2% of the total world rice crop.

Rice fields usually have a small aquatic fern called Azolla growing in the water. Azolla are inhabited by a bacterial species, Anabaena azollae, that FIXES NITROGEN, it takes inorganic nitrogen and puts it into a form that can be used by other cells. If it were not for nitrogen fixing organisms, we could net get the nitrogen that we must have to make proteins. Azolla float on the surface of the water. The relationship between the Azolla and the Anabaena is called a SYMBIOTIC ASSOCIATION, because each derive benefit from the relationship, the Azolla get nitrogen in a form they can use and the Anabaena get hydrocarbons.

Rice has traditionally been milled in a manner similar to that of wheat, the pericarp/seed coat layer and the aleurone are removed to produce POLISHED rice, which it the white rice with which we are most familiar. As in wheat bran, the aleurone layer in particular of rice contains nutrients. It is important to remove the aleurone layer from rice, as the fat in the aleurone will become rancid and limit greatly the storage life of the grain.

Traditionally, it was very difficult to produce polished rice, as the process required a lot of labor. Thus polished rice was historically available only to wealthier people, who had much more diverse diets than the rest of the population. However, with the advent of large scale mechanical rice milling equipment, it became cheap to produce polished rice. Polished rice is the preferred form as it cooks more easily and can be stored longer. Unfortunately, as polished rice became available to all, the consequences of the removal of nutrient containing bran layers began to manifest themselves among people for which rice was the staple of the diet. In particular, removal of thiamine (vitamin B) from the rice caused epidemics of a disease called BERIBERI.

Beriberi was not a problem in India, however, even though polished rice was the staple. In India, as part of the milling process, the whole grain was boiled, which allowed nutrients to diffuse into the endosperm from the aleurone, and thus nutrients were not lost during the milling process.

The rice that we buy in the store is usually fortified with the addition of vitamins, including vitamin B but dusting them with a powder containing the needed vitamins. If the rice is rinsed prior to cooking, however, the vitamins will be washed off. The vitamins will also be lost if the rice is boiled in too much water. Such fortified rice is called CONVERTED RICE. Converted rice cooks a little slower than regular rice.

Rye, Oats, Barley, Sorghum and Millet.

Rye was most likely developed as a cereal crop  because if it's hardiness. Attempts to produce a hybrid of rye  (genus Secale) and wheat (genus Triticum) to produce Tritosecale, or Triticale have in fact produced grasses that are hardier, have higher protein content and higher lysine content. Triticale, however, lacks appropriate gluten content, and bread made with Triticale flour is very heavy, and not springy, because the gluten breaks down when the dough is kneaded. Rye is commonly added to wheat to make Rye breads.

Oats, Avena sativa, is another hardy grass plant. Oats are very nutritious, with 15% protein and a good mix of vitamins, minerals and oils. Traditionally, oats were used exclusively as animal food. Romans, for example, would not eat oats. However, in places like Scotland, oats were used as food for humans, with the development of truly wonderful food items such as oatmeal, haggis and meade. We use oats quite widely in the production of breads, breakfast cereals and processed foods. In particular, it is a current fad to add oat bran to food for its nutritive value, with some believing that it reduces the chance of diseases like cancer.

Barley, Hordeum vulgare, is one of the oldest of cultivated crops. Barley was an important food crop for humans, and has also been used as food for animals. Today barley is mainly used in the production of malt for the brewing of beer and as an additive to soups. The barley used in soup is polished barley, with the polishing process removing the bran and aleurone layers, resulting in the usual drop in the nutritive value of the grain.

Sorghum and Millet

While we do not use these cereal grains as food in North America, they are widely used in Africa, India and China. Sorghum is very similar to corn, with the exception that flowers of sorghum are perfect (both male and female parts present in each flower), as opposed to corn, where flowers are either male or female. Sorghum is grown mainly for animal feed in the United States, although it is also used to make syrup.

In the United States we use millet primarily as birdseed, but it is a major cereal crop in India and China. Millet is very drought tolerant, and thus is ideal as a crop in many parts of the world.