Zea mays

Zea mays

The corn (Zea mays L., 1753) is an annual herbaceous plant belonging to the Poaceae family and is one of the most important cereals in the world.

Systematics –
From a systematic point of view it belongs to the Domain Eukaryota, Kingdom Plantae, Division Magnoliophyta, Class Liliopsida, Order Poales, Family Poaceae, Subfamily Panicoideae, Tribù Andropogoneae and then to the Genus Zea and to the Species Z. mays.

Etymology –
The term Zea comes from zēa (derived from the Greek ζειά, zeia) spelta, a plant similar to the wheat mentioned by Pliny: the name used by Linnaeus for maize. The specific epithet mays derives from maíz, of Spanish origin (in turn from mahis of caribic origin), the plant comes from central-southern America where it was the basic ingredient of Aztec cuisine. The word vulgar “maize” or “maize” derives from Turkish grain, that is “exotic, colonial” (as opposed to the Triticum aestivum).

Geographic Distribution and Habitat –
Zea mays is a plant of Central American origin, in fact most historians believe that maize was domesticated in the Tehuacán Valley of Mexico. the Olmecs and the Mayans already cultivated many varieties in the Mesoamerica area. Starting from 2500 a.C. crops spread through most of the Americas. Today the corn is cultivated in all the temperate parts of the globe.

Description –
Zea mays is the only species of the genus Zea and exists only in the cultivated state. It is a monoecious plant (male and female flowers separated on the same plant), with a single, thick and fleshy stem, rarely set. The plant has many characteristics common to other Poaceae: the stem or culm (commonly called “stocco”) distinguished in nodes and internodes; a single leaf at each node and the leaves distributed on the culm in two opposite or distal rows; each leaf consists of an expanded lamina connected to a sheath that wraps the culm. Basal nodes tend to form ramifications or culms of growth (suckers) and develop adventitious roots.
The female inflorescence, which carries the kernels, is called correctly spadix, but is more often called improperly called “panicle”, while the panicle properly said is the male inflorescence placed on the top of the stem (stocco) of the plant, which is instead sometimes improperly called “spike” because of its appearance. The kernels are fixed to the wagons and the pollen is fixed to the plant.
The root system is of a collated type and therefore quite superficial, even if in optimal pedological conditions it can go beyond 2 m of depth. There are 3 types of roots: the primary or seminal roots, which originate directly from the seed and whose function is exhausted in the juvenile stages of the plant (up to 5-6 leaves); the secondary or adventitious roots, which originate from the crown, placed at the base of the feathers, 2-3 cm below the surface of the ground, and begin to develop just 3-4 days after the emergence of the seedling; the aerial roots, which originate from the first two to three nodes above ground and have a mainly anchoring function.
The culm can have a height ranging from 50 cm to 6 – 7, but normally it is around 2-3 m. It consists of a series of nodes and internodes; the latter of increasing length from the base towards the apex. In Italian environments it has a diameter of 3-4 cm and from 8 to 21 internodes.
The leaves are arranged alternately on the two sides of the stocco, one for each node, and as the nodes, are in variable number from a minimum of 8-10 to 22-24. Under normal cultivation conditions the length of the leaves is between 30 and 150 cm and the width can reach 15 cm. It follows that the average area of ​​a leaf is around 500 cm2 and the total leaf area per plant varies from 0.5 to 1 m2. Each leaf consists of three distinct parts: the sheath, which almost completely embraces the internode above the node of origin; the flap or lamina, which represents the real leaf, of lanceolate shape with parallel longitudinal ribs of which the median one is larger; the ligula, a kind of thickening, placed between the sheath and the flap, which tightly wraps the stamina, hindering the entry of water or any parasites and determining the more or less horizontal position of the lamina.
The leaf is made up of a tegumental tissue (the epidermis), a fundamental system (the chlorophyll or mesophilic parenchyma) and a vascular system (the cribrovascular bundles). The epidermis has the function of protecting the underlying tissues from desiccation, from the action of atmospheric agents and from the attack of parasites. Moreover, both for the characteristics of its cell walls and for the presence of the stomatological devices, it regulates the transpiration and the other gaseous exchanges between the internal tissues of the leaf and the external environment.
Frequently on the epidermis there are hairs (trichomes), which if abundant, can retain the water vapor that comes out of the stomata. In this way, the air surrounding the stoma tends to be saturated with steam and this causes a slowing down in the evaporation process inside the leaf.
The caryopsis is a dry, indehiscent fruit, placed on the cob through a spongy pedicel. The peduncle connects the seed to the tetanus and then to the vascular system of the stem.
The endosperm constitutes 85% of the weight of the ripe caryopsis, the embryo 10% and the pericarp with the pedicel 5%. The endosperm consists mainly of starch, the main reserve compound of plants.
The caryopsis contains about 4% of high quality oils due to the presence of unsaturated fatty acids (linoleic and oleic).
When ripe, kernels have colors ranging from white to black. The coloring is determined by the production of: carotenoids, which give the yellow-orange color, and anthocyanins, which give colors from red to black.
A well-developed spike produces approximately 800 kernels of corn. The caryopsis is basically composed of three parts: the germ, the endosperm and the pericarp. During the development of the grain, the photosynthesis products are transported inside the grain through the pedicel.
The chemical composition of the grain of maize is shown in the table. A dried kernel with 16% moisture content, on average contains 71% starch, 10% protein, 4.5% fat and other substances such as pentosans, fibers, cellulose and lignin, sugars and carotenoids.

Cultivation –
Corn is a hot season plant that requires abundant light and higher growth temperatures than other cereals. Temperatures below 10 ° C or above 45 ° C result in an interruption of growth or in any case a very slow development. The best crops are found in areas where the crop takes from 130 to 150 days to mature. The maturation rate is influenced by the length of the day and short photoperiods favor early blooms. For the cultivation technique, the following sheet can be consulted.

Uses and Traditions –
Zea mays, according to archaeological and historical findings, should have been tamed about 10,000 years ago by the indigenous peoples of central Mexico and then in prehistoric times. According to research in 2002, it appears that corn is the result of a single domestication in southern Mexico dating back to around 9,000 years ago.
After the discovery of the Americas, European explorers and traders introduced it to other countries. Present in the early sixteenth century in Spain and Portugal, it spread rapidly in southern France, northern Italy, in the Balkans, then in other parts of the Mediterranean basin, along the west coast of Africa, and arrived in China around 1540-50 . Maize, or maize, today represents the food base of the populations of Latin America and some regions of Europe and North America. In temperate regions it is mainly intended for feeding domestic animals, in the form of grains, flours or other feeds, or as silage, generally collected when waxy. It is also intended for industrial transformation for the extraction of starch and oil or fermentation, in order to produce by distillation alcoholic beverages or bioethanol for energy purposes.
This plant, with all its varieties, hybrids and transgenic derivatives, is one of the most important cereals, widely cultivated both in the tropical and in the temperate regions, in the latter case in the spring-summer cycle.
Among the various uses of corn we find the grinding to create flour, the squeezing from which corn oil is obtained and fermentation and distillation in alcoholic beverages such as bourbon and whiskey. Corn also finds use in the chemical industry.
From a nutritional point of view the properties of this plant are modest. Apart from a good amount of carbohydrates, corn contains few nutrients and few B vitamins and PP group, which are present in non-assimilable form. In addition, its protein component is low in lysine and tryptophan, two amino acids essential for food. For this reason, in times of past and famine, the disease of pellagra also struck in Italy, and especially in Veneto and Friuli, the peasants who, for lack of other kind of food, fed almost exclusively with polenta.
The stigmas of this plant can be taken through herbal teas, these produce a diuretic effect and are recommended in calculosis and cystitis. From corn you can make an oil that, applied to the skin with a light massage, makes it softer and more elastic.
Moreover, corn can be used to make a starch to produce biodegradable plastics to make, for example, bags for the collection of biodegradable urban waste (wet). These bags decompose and return to nature through the composting process.
The European community has adopted the Reg. 1126/2007 which foresees a limit of presence in the fumonisins maize (indicated by many researches as responsible for oncological risk), a toxin produced by the fungi parasites of the corn. Since October 2007, a limit of 4,000 parts per billion has been set in maize for human food consumption.

Preparation Mode –
The history of human food starting from corn is lost in the mists of time. In Aztec cuisine, corn was the essence of the meal, as is rice for the Asian people and wheat for us Europeans. Nowadays this cereal supports the daily diet of many people who consume it with innumerable ways and recipes. They range from boiled corn with cobs, popcorn (prepared from a specific variety of corn) to polent consumed in many continents. In addition, corn is part of the preparation of salads, pies, fillings, biscuits, etc.
Being one of the world-wide cereals, its preparation and its use for human nutrition, obviously suffer from the various traditions and popular cultures.

Guido Bissanti

Sources
– Acta Plantarum – Flora of the Italian Regions.
– Wikipedia, the free encyclopedia.
– Treben M., 2000. Health from the Pharmacy of the Lord, Advice and experience with medicinal herbs, Ennsthaler Publisher
– Pignatti S., 1982. Flora of Italy, Edagricole, Bologna.
– Conti F., Abbate G., Alessandrini A., Blasi C. (edited by), 2005. An annotated checklist of the Italian vascular flora, Palombi Editore.

Warning: Pharmaceutical applications and alimurgical uses are indicated for informational purposes only and do not in any way represent a medical prescription; there is therefore no liability for their use for curative, aesthetic or food purposes.




Leave a Reply

Your email address will not be published. Required fields are marked *