Classification
Kingdom Plantae
Division Magnoliophyta
Class Liliopsida
Order Cyperales
Family Poaceae
Subfamily Panicoideae
Genus Zea
Species Zea mays
Subspecies mays
Introduction
Maize (Zea mays L., 2n=2x=20, family Poaceae) is the world’s most significant cereal crop, behind wheat and rice, and is the first in Sub-Saharan Africa (SSA), where it provides food, income, and livelihood to over 80% of the people.
Maize’s Origin
The word “maize” is supposed to have evolved from the Sarawakian word “mahiz” (Ortega et al., 1980). The maize crop is thought to have originated 10,000 years ago in Meso America (today’s Mexico, Guatemala, and Honduras) from wild grasses known as teosintes. Maize and teosinte coexist as independent entities because of a low rate of gene flow (intercross) (AGOGTR, 2008). In terms of genome assembly, maize is related to sorghum (Sorghum bicolor L.). The two crops are thought to have split up roughly 12 million years ago.
Maize is said to have been domesticated for use as a food source some 6000 years ago. The crop was initially introduced to the Americas after European travelers discovered the continent in the 15th century, and it then expanded to Sub-Saharan Africa and the rest of the world. Each region has developed its maize varieties that have adapted to its environment over time.
Maize Taxonomy
The cultivated maize, commonly known as “corn” in some areas of the world, is a member of the genus Zea, which belongs to the Andropogoneae tribe of the Poaceae family, subfamily Panicoideae.
There are six other wild species of maize in the same genus, but they are wild grasses (known as teosintes) and are not cultivated. Except for Zea perennis (Perennial teosinte with 2n=2x=40), all six maize species have the same chromosome number of 2n =2x=20.
Maize Plant
1. Maize is a monoecious annual plant having separate male and female blooming parts on the same plant.
2. It is a tall, determinate monocotyledon plant.
3. Shanks form in the leaf axis and evolve into a female inflorescence (an ear). More than one shank may form on a single maize plant depending on the type, but usually, only 1-2 develop into economically viable ears (cobs).
4. Several leaves (husks) cover the ears, and each cob bears an even number of rows (8-30) of kernels.
5. Each ovary has one ovule that develops into a kernel. Between 300 and 1000 kernels are included in one ear of maize.
6. The maize stalk’s apical meristem develops into a tassel, which consists of a central spike and up to 40 lateral branches containing male flowers.
7. A robust peduncle supports the tassel structure on top of the plant.
8. The protective epidermis protects layers of sclerenchyma tissues in maize stems, resulting in a sturdy stalk. Unlike their temperate relatives, tropical/sub-tropical species are generally taller.
Root System
A normal maize plant can produce 4-6 adventitious roots that are about identical in size. Because of their adventitious nature, maize roots are shallow and lack a tap root. Nodes beneath the soil surface give rise to adventitious roots. The root length can reach 1.5 meters laterally and 2.0 meters deep. The roots are essential for water and nutrient uptake from the soil.
STEM
A standard maize plant has a single stem that is about 0.5-5 m tall, depending on the variety and environmental conditions in which it is grown (measured from the soil surface to the point where flag leaf is attached to the peduncle). The stem is solid, cylindrical, and divided into nodes by internodes. Internodes are cylindrical in the upper part of the plant and alternatively grooved in the lower portion of the plant, with a bud in each groove, and one or two lateral branches in the leaf axils. Grooves are necessary for optimal ear placement.
LEAF
The photosynthetic organs responsible for food generation are leaves. The higher leaves are more responsible for light interception and contribute a significant amount of photosynthate to grain filling. On a single plant, 8-30 leaves can grow and are spirally aligned on the stem. Stomata are distributed in rows throughout the entire leaf surface, with more on the underside than on the upper surface. The leaves curl inwards, water loss due to evaporation is reduced because the leaf surface exposed to the air is decreased.
FLOWER
Maize is a monoecious plant, meaning it has two morphologically completed flowers (male and female). The male flower is just made up of stamen, whereas the female flower is made up of pistil. Although the two reproductive organs are on the same plant, they are located on opposite sides of the plant.
Tassel (Male flower): Tassel is a male flower that grows on the top of a maize plant and is supported by a peduncle. The apical meristem of the maize stalk produces the tassel. Normally, each maize plant has only one tassel, which consists of a central spike (tassel rachis) and 20-50 tassel limbs (branches). Each male stamen has three anthers swinging out on a short filament, and each male stamen has numerous male stamens. Anthers are male organs that produce and disperse millions of pollen particles into the air.
Female flower: The female reproductive portion of maize is the ear, which develops from the shanks (stalk-like structures) that develop from the axillary bud to the middle of the stem length.
Fruit and Seed
After fertilization, maize seed is created, which is a combination of both fruit and seed (also known as kernel or grain). Seed is primarily composed of 72 percent starch, 10% protein, 4% fat, and 1.4 percent ash, with an energy density of 365 Kcal/100 g. Maize seed also contains riboflavin and nicotinic acid, as well as vitamins A and E. It is a single-seeded dry indehiscent fruit (caryopsis) with three primary compartments: the fruit wall (brand), the endosperm, and the embryo.
Reproduction system in Maize
A sexually reproducing creature with well-developed male and female reproductive systems, the maize plant is a sexually reproducing organism. Although no evidence of asexual reproduction in maize has been identified, under advanced laboratory circumstances, vegetative components of maize, such as embryos, can be managed using tissue culture techniques to grow into a whole morphological corn plant. Maize reproduction requires several phases of development.
Pollination and Fertilization
Pollination is the process of pollen grains being transferred from the anther to the silk. Fertilization is the process by which male pollen gametes combine with female ovule gametes to generate a zygote. Only when cell division is complete can fertilization take place. Pollen grains are first transferred onto the female reproductive organ (silk) by wind, animals (particularly insects), or direct physical contact between plants. Maize, unlike other creatures, has two types of fertilization: embryo and endosperm fertilization.
Maize seed Production
Any component of a crop that geminates or reproduces to form the same crop and meets expectations in terms of desired qualities is referred to as a seed. As a result, the seed must be made available to farmers to increase productivity. However, because maize is an out-crossing crop, any seed production activity (OPV or hybrid) must closely adhere to the laws and standards. To produce maize seeds of suitable quantity and quality, various management approaches and techniques have been used.
PLANTING
Planting is the act of placing a seed into a seedbed in preparation for the growth and development of a crop. Maize planting begins as soon as the land preparation is finished and the soil moisture and temperature are appropriate. Maize planted in soil under unfavorable environmental circumstances, such as drought, excess water, or severe soil temperatures, may not germinate and hence perish. Maize is usually planted at a depth of 5 cm (heavy soil) to 10 cm (light soil) (sandy soil). Spacing and plant population number are two further techniques to consider. The amount of the plant population is governed by whether the system is rain-fed or irrigated, as well as the current environmental circumstances and the variety used. When opposed to a rain-fed system, maize planted under irrigation usually has a higher plant density.
Uses of Maize
1. Maize is important for industrial purposes as well as animal feed in SSA, where it is directly used by the majority of the population as food, drinks, animal feeds, and cooking energy.
2. Maize is processed into a variety of products, including starch, corn syrup, sweeteners, oil, beverages, glue, alcohol, and fuel ethanol.
3. Because maize seedlings have inadequate root and shoot systems, they must rely on nutrients stored in the caryopsis beneath the earth.
4. The seedling begins to capture more sunlight and manufacture its food as the leaves develop and the roots expand (photosynthesis).